Drivetrain questions............

[NavyCPO]

Ok so I'm building a 383 for my monte and I'm going to pull the original 350 2bbl, have hardened seats and a valve job on the original heads, re-seal and completely re-gasket the original motor then preserve it and put it on a stand in case I ever sell the car I can let the buyer have his choice of all original or my version of the monte.  So back to my 383 build, I can do the engine no problem, but it's going to be a pretty healthy 383, I'm estimating 450-500 HP.  I bought a 2500 stall converter and I also bought a 700R4 complete core and was going to have it rebuilt and put it in the Monte for the overdrive, but when I talked to the guy at the local transmission shop he said that the 700R4's are not a very strong transmission, and you have to set them up to run without the electrical stuff and I hear folks constantly battling the TV cable etc. etc. so now I'm leaning towards just keeping my 3 speed Turbo 350 tranny and just put a shift kit in it.  My Monte only has about 70k original miles on it (a true survivor) and I thought about rebuilding it with HP clutches and shift kit, but I'm thinking maybe I'll just have a shift kit in it and use up whatever remaining life the stock clutches have left in them.  Tranny rebuild with HP clutches will be 1-1.2k even just on the bench, me pull and carry home, but  shift kit I figure maybe $300?  Been a while since I messed with this stuff.  But then I'm going to have to also do something with my I'm assuming 2.73 1 legged rearend.  So I've been thinking about getting a posi and putting some gears in it since the cam wants gears too.  I have the 8.2" 10 bolt and I am thinking of going with 3.55 or maybe 3.31 gears.  Any recommendations on which way to go here?  And when I change the gears I'll have to change the plastic gear in the tail shaft of the tranny to match the new gears because I want my factory speedometer to be right.  Does anyone know where I can find a link or a list of the correct color code gear to use with these gear ratios?  I know they are color coded for different gear ratios but I wouldn't know where to find that info or where to find the part either.  I do know how to change it though! LOL I also have a T400 tranny sitting on the floor of my shop that I believe to be a good one that may have already been built a bit, my tranny guy said the 350 is just as good as the T400.  If I go with the T400 or the 700R4 I'd have to find a driveshaft shop and shorten the drive shaft and on the 400 go with bigger Yoke and probably those special U-joints (I forget what you call them, short on one side and bigger on the other side), so I think I'll just stay with my T350 for now and may consider a tranny swap later depending on the feedback I get about both of those other tranny's.  So blah blah blah, what I'm looking for is......

1. Feedback on the 700R4 vs the T350/T400.  What do you think of you 700R4's?

2. Link or info about which speedometer gear to get when I change my differential gear ratio and help on where I can get it from.

3. Opinions on 3.31 or 3.55 gear ratio.  I thought about 3.73 to but I'm not going to Race the car and I think I'd be revving too high to get 70-80mph highway speeds these days.  And with a 3 speed tranny even the 3.55 might be a stretch but I want a good hole shot and be able to turn the tires easily and have a good 1/4 mile time.

[714024SPEED]

Sounds like you have a good plan for the engine. I would use the turbo 350 with the 3:31 gear. I think you would be happy with that gear . I would also recommend a Detroit trutrac position unit,have had good luck with them.

[Jason72]

IMHO, the 700r4 is not the best choice if it’s just a stock rebuild. If the transmission shop knows what they are doing it can be done. Your driving style at your power level will have a huge impact on this as well. You could always go with a well built 200r4. They can be built much stronger and are much better than the 700

as far as gears for the speedometer, I’ll look in my notes for the guy I use when I get to my shop today. I also think tci has the information on their website, some sort of calculator. 
 

gears in the rear will depend on the transmission and what your using the car for. So decide on that after you pick a transmission

[Jason72]

https://www.tciauto.com/speedometer-gear-calculator

speedo gears

[stangeba]

Great set of driveline questions!

I wonder if there is a website where your questions and others like them are answered?

My former boss (current brother in-law) Did this sort of thing for the 235 cu in INLINE SIX Cylinder engine.

 

Langdon's Stovebolt Engine Co. is not in business anymore but Tom still has a ton of used 6 Cyl engine parts for sale.

[Scott S.]

Hey Wilbur,

I went through a lot of what you're planning, and you'll probably find contrary opinions no matter which way you go. 

I chose to go the 200r4 route..... But most of the mechanics I know recommended the 700r4 for strength. 

With the 700, you'll have to make a few alterations as opposed to the 200r4's ability to pretty mush bolt straight in. 

As for the T.V. cable and lock up torque.... T.C.I. and Summit, as well as B&M all make kits to make the wiring issues a snap.

The real secret is finding a transmission guy that specializes in high performance rebuilds. The guy I used had done several, and has over 40 years in the business. So he knew what needed to be upgraded. It cost me a little over $3000.00 Can.

As for the speedo gears, T.C.I. has a chart to figure out what to use that includes wheel diameter in the calculation. Helps with the accuracy. 

With regards to the differential, the 8.2" isn't probably the best choice for anything other than stock..... There are still pieces available, but if you plan on lighting up the tires,it won't take it for long.

I swapped in a factory 12 bolt, but for the price, aftermarket ones may be a stronger option. 

Presently running 3.31 gears..... and with the overdrive my LT-1 spec 350 turns about 2250-2300 rpms at 70 mph. But it doesn't have the off the line bite I was hoping for. The 3.55 gears would give you more of that, but you'd start getting rpms in the 2500 range at highway speeds. 

I've added a few things that might come in helpful. Best of luck on your "adventures".   

Scott.

GearRatioChart.pdfGearRatioChart.pdf

[72 Monte Carlo]

I agree with Scott, and I was also thinking that a very nice built TH200-4R trans with give you overdrive when you need it on the highway but give you a nice solid trans to play with on the strip/street. 

[bob 71]

ive got a turbo 350 rebuilt w/shift kit n goodies 2500 stall converter 12 bolt posi 355 gears 28 inch tall tires. 65 mph turning 2800/3000 rpm. 396 small block 

[Scott S.]

21 hours ago, 72 Monte Carlo said:

I agree with Scott, and I was also thinking that a very nice built TH200-4R trans with give you overdrive when you need it on the highway but give you a nice solid trans to play with on the strip/street. 

The mechanic that built my 200r4 built and tested it for a limit of 750 hp.

Don't think I'll be pushing that anytime soon.  

[420ponies]

My .02 Cents, I've had a 2004r with a 420 Hp SBC in my Monte since'13 ( I'm thinkin'), Worked well with the 2:73 ratio posi. I was under the assumption it was a 3:42 gear from a Camaro (wrong again). Anyway, If you could find a 2004r it would give about 500 rpm less in OD. A turbo 350 has a better (lower ),1st gear than a Turbo 400. You need to move that car faster off the start no matter what. Now, they do make a lower 1st gear for a turbo 400 (what I have in mine with the new 427 BBC). I replaced the rear axle with a built 3:73 Yukon posi, Richmond gears, Moser street axles, disc brakes. Cook brothers driveshaft with spicer u-joints. The stall converter is 2,500 stall (as with the 2004r), stall was around 2,200 with that set-up. At 70mph with 257/60/15 in OD was around 1,900rpm. 1st-2nd was very firm shift. With the 2004r it had a toggle switch to lock out the OD. Sounds like you have good plan. Now about that 383......... are we talking aluminum heads,JE pistons, or a Scat Crank Kit? Ohio Crankshaft  has a good kit for SBC 383. Like to see how you are making out with the build.

 

[NavyCPO]

On 5/8/2025 at 7:27 AM, Jason72 said:

IMHO, the 700r4 is not the best choice if it’s just a stock rebuild. If the transmission shop knows what they are doing it can be done. Your driving style at your power level will have a huge impact on this as well. You could always go with a well built 200r4. They can be built much stronger and are much better than the 700

as far as gears for the speedometer, I’ll look in my notes for the guy I use when I get to my shop today. I also think tci has the information on their website, some sort of calculator. 
 

gears in the rear will depend on the transmission and what your using the car for. So decide on that after you pick a transmission

I think I may stick with my TH350 tranny.

[NavyCPO]

On 5/8/2025 at 7:29 AM, Jason72 said:

https://www.tciauto.com/speedometer-gear-calculator

speedo gears

Thank You!

[NavyCPO]

On 5/8/2025 at 2:17 PM, Scott S. said:

Hey Wilbur,

I went through a lot of what you're planning, and you'll probably find contrary opinions no matter which way you go. 

I chose to go the 200r4 route..... But most of the mechanics I know recommended the 700r4 for strength. 

With the 700, you'll have to make a few alterations as opposed to the 200r4's ability to pretty mush bolt straight in. 

As for the T.V. cable and lock up torque.... T.C.I. and Summit, as well as B&M all make kits to make the wiring issues a snap.

The real secret is finding a transmission guy that specializes in high performance rebuilds. The guy I used had done several, and has over 40 years in the business. So he knew what needed to be upgraded. It cost me a little over $3000.00 Can.

As for the speedo gears, T.C.I. has a chart to figure out what to use that includes wheel diameter in the calculation. Helps with the accuracy. 

With regards to the differential, the 8.2" isn't probably the best choice for anything other than stock..... There are still pieces available, but if you plan on lighting up the tires,it won't take it for long.

I swapped in a factory 12 bolt, but for the price, aftermarket ones may be a stronger option. 

Presently running 3.31 gears..... and with the overdrive my LT-1 spec 350 turns about 2250-2300 rpms at 70 mph. But it doesn't have the off the line bite I was hoping for. The 3.55 gears would give you more of that, but you'd start getting rpms in the 2500 range at highway speeds. 

I've added a few things that might come in helpful. Best of luck on your "adventures".   

Scott.

GearRatioChart.pdfGearRatioChart.pdf 44.43 kB · 2 downloads

Thank you for all the helpful info Scott and for taking the time to upload photo's too.  Did I tell you guys the story about my '68 Camaro with a 540 cid BBC with full Lunati Pro Mod Rotating Assy, @ 740 HP motor alone and a BIG SHOT N2O system jetted at 225 HP and my 8.2" Richmond Geared, Moser 28 spline axeled, c-clipped rearend without a stud girdle?  I never had a problem with that Rearend despite the huge HP BBC in the car.  Granted, I only had slapper bars and could never really hook-up and truly Launch, but I used to burn the crap out of those tires all the time and that lil 8.2" held up fine.  Personally, I think they are under-rated. LOL

[NavyCPO]

On 5/8/2025 at 4:54 PM, 72 Monte Carlo said:

I agree with Scott, and I was also thinking that a very nice built TH200-4R trans with give you overdrive when you need it on the highway but give you a nice solid trans to play with on the strip/street. 

Ok, now I've been out of it for a while, but here's my extent of transmission knowledge, I know there is a Powerglide, TH350, TH400, 700R4, 4l60, 4l80 full stop.  Never heard of a 2004R and transmissions ain't my thang, "there's ALIEN STUFF IN THERE" way beyond my comprehension.  I leave those to the experts, pressures, transmission data are all greek to me.  $3k for a transmission build is out of my league, $1k for a transmission rebuild is about as much as I want to pay for a bench rebuild where I bring you the tranny, you rebuild it and I pick it up and reinstall it.  For $3k I expect to get a ………..a beer and a shot at his wife, DOH!! LOL  But seems the general consensus is that the 2004R is STRONGER than the 700R4 if I want to go with an OD Tranny, But a 700R4 is not ALL THAT BAD.  I won't be taking it to the strip, not doing a 4 link, ladder bars or none of that, just want to be able to spin the tires readily, maybe hook a reasonable amount for some Saturday night fun.  I feel like I'm still a kid when it comes to cars.

[NavyCPO]

On 5/9/2025 at 1:37 PM, bob 71 said:

ive got a turbo 350 rebuilt w/shift kit n goodies 2500 stall converter 12 bolt posi 355 gears 28 inch tall tires. 65 mph turning 2800/3000 rpm. 396 small block 

So if I went with the 3:31 I might be expecting 2500-2800 maybe?  Good Guess?  I like the sound of that 396 small block, how'd you get that?  I just picked up a virgin 400 block today and I've always wanted to build a 427 small block, might do that someday.  May do a 400 again is I can stay with the standard bore, maybe a 406 if I have to bore, but I think it'd be so cool to put a 4" stroker crank in it with standard bore and build a true 427 sbc.  But what I'm finding so far on Desktop Dyno is that I don't really gain that much horsepower over a 383 build, but it does make signigicantly more TQ.  Only showing about 20HP gains over 383 but that's sticking with same 200cc heads, cam, 800cfm carb etc.  May have to play with the other goodies to get the real gains from those extra cubic inches and maybe that's just too much for a small block with those BBC heads.  Things that make you go hmmmmmmm..........................

[NavyCPO]

On 5/11/2025 at 7:19 AM, 420ponies said:

My .02 Cents, I've had a 2004r with a 420 Hp SBC in my Monte since'13 ( I'm thinkin'), Worked well with the 2:73 ratio posi. I was under the assumption it was a 3:42 gear from a Camaro (wrong again). Anyway, If you could find a 2004r it would give about 500 rpm less in OD. A turbo 350 has a better (lower ),1st gear than a Turbo 400. You need to move that car faster off the start no matter what. Now, they do make a lower 1st gear for a turbo 400 (what I have in mine with the new 427 BBC). I replaced the rear axle with a built 3:73 Yukon posi, Richmond gears, Moser street axles, disc brakes. Cook brothers driveshaft with spicer u-joints. The stall converter is 2,500 stall (as with the 2004r), stall was around 2,200 with that set-up. At 70mph with 257/60/15 in OD was around 1,900rpm. 1st-2nd was very firm shift. With the 2004r it had a toggle switch to lock out the OD. Sounds like you have good plan. Now about that 383......... are we talking aluminum heads,JE pistons, or a Scat Crank Kit? Ohio Crankshaft  has a good kit for SBC 383. Like to see how you are making out with the build.

 

Well I'm just a poor country boy, I think I have TRW Forged Pistons in my shortblock but it's just an old stock ext. balanced cast stock 400 crank with stock 5.7 chevy I beam rods, chinese aluminum 200cc 2.02 int/1.6 exh valves, nothing fancy (my BBC 540 in my old' '68 Camaro I had the good stuff AFR fully CNC Ported Race Ready 335cc BBC Heads World Products 540 block, Lunati all forged PROMOD rotating assembly, TM2R Intake, Demon 850, N20 Big Shot System, MSD 7AL, MSD billet Distributor, Griffin Aluminum Radiator, TCI Reverse pattern Manual Valve Body T400, etc. etc) oh back to my 383 valve train 1.5 I think they're ProForm Roller Rockers aluminum, haven't decided on pushrods yet, 3/8" screw in studs and guide plates, Crane Stud Girdle (to add strength to the 3/8" studs), may go with some thicker walled .080 or maybe .120" 5/16 push rods, Edelbrock 800CFM 1413, Torker II single plane intake and either a Edelbrock Performer RPM, but I'm leaning towards the Comp Cams XE284H flat tappet camshaft.  Again I'm a poor boy right now and ROller setups are just getting ridiculously priced, maybe later, but I'm also considering a Comp Big Muthr Thumpr that I just saw on Marketplace for $150.  With machine work and all I'm on a shoestring budget right now.  Now having said all that, I've talked to guys that have built some killer motors with so called JUNK Parts that make really good power and will run up and down the drag strip all day long.  Just sayin'..................  And by the way, I haven't actually started on the build yet, the 383 is sitting on the stand waiting to get put back together, it was running when I pulled it, but needed cam bearings for a low oil pressure at idle issue.  Just need to get the snout threads repaired on the crank, maybe get it polished, hone the block from sitting, going back with the same pistons and new rings/bearings/gaskets then adding the new heads/intake and carb and HEI distributor but I am about to get started on it real soon.  Still gathering parts and making a plan right now.  I'm still undecided if I'm actually going to put it in my Monte or not.  My '70 Monte is a True Survivor with only 69k miles on it, never went through a showroom as the original owner worked at the GM plant in Van Nuys, CA and purchased it right off of the assy line and has been garage kept it's entire life.  They moved back to OKlahoma, He died, wife had it, She died passed it to the daughter who immediately put it up for sale, now I have it.  If I do put it in the Monte, I'm taking the original motor getting the heads reworked with hardened seats, resealing and regasketing the entire motor and will preserve it and store it on an engine stand in case I want to sell the car someday.  I'm thinking about getting another car now to play with instead (I like Nova's, Chevelle's esp 66 and 67's, El Camino's and maybe even another Monte that is not so Original that I would feel better about playing with and that might actually have a 12 bolt in it with a SBC 400)and if I do that then my '70 Monte might only get a mild cam, dual exhaust and I'll switch to a 4bbl intake as unfortunately my Monte is a 350 2bbl, but she is a sweety.

[Scott S.]

10 hours ago, NavyCPO said:

Well I'm just a poor country boy, I think I have TRW Forged Pistons in my shortblock but it's just an old stock ext. balanced cast stock 400 crank with stock 5.7 chevy I beam rods, chinese aluminum 200cc 2.02 int/1.6 exh valves, nothing fancy (my BBC 540 in my old' '68 Camaro I had the good stuff AFR fully CNC Ported Race Ready 335cc BBC Heads World Products 540 block, Lunati all forged PROMOD rotating assembly, TM2R Intake, Demon 850, N20 Big Shot System, MSD 7AL, MSD billet Distributor, Griffin Aluminum Radiator, TCI Reverse pattern Manual Valve Body T400, etc. etc) oh back to my 383 valve train 1.5 I think they're ProForm Roller Rockers aluminum, haven't decided on pushrods yet, 3/8" screw in studs and guide plates, Crane Stud Girdle (to add strength to the 3/8" studs), may go with some thicker walled .080 or maybe .120" 5/16 push rods, Edelbrock 800CFM 1413, Torker II single plane intake and either a Edelbrock Performer RPM, but I'm leaning towards the Comp Cams XE284H flat tappet camshaft.  Again I'm a poor boy right now and ROller setups are just getting ridiculously priced, maybe later, but I'm also considering a Comp Big Muthr Thumpr that I just saw on Marketplace for $150.  With machine work and all I'm on a shoestring budget right now.  Now having said all that, I've talked to guys that have built some killer motors with so called JUNK Parts that make really good power and will run up and down the drag strip all day long.  Just sayin'..................  And by the way, I haven't actually started on the build yet, the 383 is sitting on the stand waiting to get put back together, it was running when I pulled it, but needed cam bearings for a low oil pressure at idle issue.  Just need to get the snout threads repaired on the crank, maybe get it polished, hone the block from sitting, going back with the same pistons and new rings/bearings/gaskets then adding the new heads/intake and carb and HEI distributor but I am about to get started on it real soon.  Still gathering parts and making a plan right now.  I'm still undecided if I'm actually going to put it in my Monte or not.  My '70 Monte is a True Survivor with only 69k miles on it, never went through a showroom as the original owner worked at the GM plant in Van Nuys, CA and purchased it right off of the assy line and has been garage kept it's entire life.  They moved back to OKlahoma, He died, wife had it, She died passed it to the daughter who immediately put it up for sale, now I have it.  If I do put it in the Monte, I'm taking the original motor getting the heads reworked with hardened seats, resealing and regasketing the entire motor and will preserve it and store it on an engine stand in case I want to sell the car someday.  I'm thinking about getting another car now to play with instead (I like Nova's, Chevelle's esp 66 and 67's, El Camino's and maybe even another Monte that is not so Original that I would feel better about playing with and that might actually have a 12 bolt in it with a SBC 400)and if I do that then my '70 Monte might only get a mild cam, dual exhaust and I'll switch to a 4bbl intake as unfortunately my Monte is a 350 2bbl, but she is a sweety.

A sweetie with a documented history...... And that makes her more valuable as an original than modifying her.   

[Scott S.]

10 hours ago, NavyCPO said:

So if I went with the 3:31 I might be expecting 2500-2800 maybe?  Good Guess?  I like the sound of that 396 small block, how'd you get that?  I just picked up a virgin 400 block today and I've always wanted to build a 427 small block, might do that someday.  May do a 400 again is I can stay with the standard bore, maybe a 406 if I have to bore, but I think it'd be so cool to put a 4" stroker crank in it with standard bore and build a true 427 sbc.  But what I'm finding so far on Desktop Dyno is that I don't really gain that much horsepower over a 383 build, but it does make signigicantly more TQ.  Only showing about 20HP gains over 383 but that's sticking with same 200cc heads, cam, 800cfm carb etc.  May have to play with the other goodies to get the real gains from those extra cubic inches and maybe that's just too much for a small block with those BBC heads.  Things that make you go hmmmmmmm..........................

You'll probably be running around 2800 rpm @ 60 mph with those gears. 

Montelishi was pulling 2700 rpm @ 60 mph with 2.73 gears. 

[Scott S.]

10 hours ago, NavyCPO said:

Ok, now I've been out of it for a while, but here's my extent of transmission knowledge, I know there is a Powerglide, TH350, TH400, 700R4, 4l60, 4l80 full stop.  Never heard of a 2004R and transmissions ain't my thang, "there's ALIEN STUFF IN THERE" way beyond my comprehension.  I leave those to the experts, pressures, transmission data are all greek to me.  $3k for a transmission build is out of my league, $1k for a transmission rebuild is about as much as I want to pay for a bench rebuild where I bring you the tranny, you rebuild it and I pick it up and reinstall it.  For $3k I expect to get a ………..a beer and a shot at his wife, DOH!! LOL  But seems the general consensus is that the 2004R is STRONGER than the 700R4 if I want to go with an OD Tranny, But a 700R4 is not ALL THAT BAD.  I won't be taking it to the strip, not doing a 4 link, ladder bars or none of that, just want to be able to spin the tires readily, maybe hook a reasonable amount for some Saturday night fun.  I feel like I'm still a kid when it comes to cars.

The 200r4's were most popular in the '85-'87 Monte SS's, Buick Grand Nationals/T-Types, Hurst Olds, and some Pontiac Grand Prix...... But could be ordered in Camaros/Firebirds too. 

The one's made from '82-'84 can be found in just about any G.M. model, including Cadillacs. They were upgraded in '85, but if you're having it rebuilt above stock specs, either one will work. 

[Scott S.]

11 hours ago, NavyCPO said:

Thank you for all the helpful info Scott and for taking the time to upload photo's too.  Did I tell you guys the story about my '68 Camaro with a 540 cid BBC with full Lunati Pro Mod Rotating Assy, @ 740 HP motor alone and a BIG SHOT N2O system jetted at 225 HP and my 8.2" Richmond Geared, Moser 28 spline axeled, c-clipped rearend without a stud girdle?  I never had a problem with that Rearend despite the huge HP BBC in the car.  Granted, I only had slapper bars and could never really hook-up and truly Launch, but I used to burn the crap out of those tires all the time and that lil 8.2" held up fine.  Personally, I think they are under-rated. LOL

Like I was saying, there are parts to upgrade an 8.2", but as a stock unit, they could be prone to breakake. 

One thing of note also is that a Camaro is a few pounds lighter and the axles are a few inches narrower. Not to mention that they were also the heavier version as well.   

People love to abuse Camaros...... It's just fun. 

[NavyCPO]

On 5/14/2025 at 1:08 PM, Scott S. said:

Like I was saying, there are parts to upgrade an 8.2", but as a stock unit, they could be prone to breakake. 

One thing of note also is that a Camaro is a few pounds lighter and the axles are a few inches narrower. Not to mention that they were also the heavier version as well.   

People love to abuse Camaros...... It's just fun. 

These are good points and I take note.

[Jason72]

I “built” my 8.2.  
axles, carrier, c clip eliminators and gears, I could have bought a moser muscle pack and been done…

[BobW]

This will help you figure out the numbers: https://spicerparts.com/calculators/transmission-ratio-rpm-calculator

My new to me motor with a mild cam of unknown heritage, idles at 900-1000rpm. Engaging drive drops to 600 rpm and pulls fairly strong, the stock TH350 converter stall feels too low, around 1200 according to search. I'll have to pay someone to drop the trans to change the converter, so at that point I'm considering changing to a 200r4.

Stock TH350 has 151K on it, works fine, but if it comes out, rebuild & new converter $$ would balance with the 200r4.

Then I get into rear gearing.........

[Scott S.]

I like the overdrive of the 200r4 for the highway, which is where I do most of my driving. 

[BobW]

15 hours ago, Scott S. said:

I like the overdrive of the 200r4 for the highway, which is where I do most of my driving. 

What are you 200r4 guys using to engage the converter lock? Is there a simple manual switched "1 wire" conversion?