Jump to content

Question about 700R4 Tranny


McCall72

Recommended Posts

Just took the Monte for a little highway trip and just can't take the TH350 2:73 combo anymore so I'm in the market for a 700R4 and will be switching to a 3:55 rear gear. Now I'm searching Craigslist around my area and have found several pretty cheap. I'm going to have which ever one I buy rebuilt, but I need to know what to look out for in terms of year-Will any year work for my '72? Also, will the drive shaft need to be shortened?

Link to comment
Share on other sites

It is worth that as a core deffinetly. I think in 85 is when they swapped to to 30 spline input shaft vice the 27 spline. The 30 spline is suppose to be stronger, but if you get the 27 spline and are going to get it rebuilt anyway they can up date it no problem.

 

The 700R4 is 3 inches longer than a 350 Turbo. so you would have to shorten your drive shaft. I currently have a 27 spline 700R4 but don't have the correct torque converter for it. So to keep from having to get my drive shaft shortened even more (its a custom shaft from putting an Olds 3.73 posi 12 bolt in my Monte) I'm going to find me a 200-4r which is the same lenght as the 350 Turbo.(All three transmissions can use the same output yoke to my knowledge.) The 200-4r has more evenly spaced gearing and a slightly higher OD ratio (0.67 vice 0.70) if I'm not mistaken... The 200-4r's can also take some abuse, especially when properly prepped... Buick GN Turbo's came with them stock.

Link to comment
Share on other sites

I don't want to revist this post again lol. All kidding aside I did a post last year with the different trans we have turbo 400 turbo350 and a 700r4. 92 would be a good stopping point for a 700r4 or a 4l60. 93 GM came out with the 4l60e which has a computer to control the trans. Now I am a odd ball and probably one of the few who is running a 700r4 trans with 2.73 gears and a power trax unit, my rear tires are 26" high(255/50/16) and in o.d I'm turning 1727rpm's @ 70 mph. From a stand still that 3.06 first gear and the 2.73 is fun. Car hasn't been out of the garage since Labor day but we did put 40 miles on it round trip to a show and burn up a 1/4 tank of fuel. Aaron I would give 700r4.com a call and talk to them they did the one in my Monte along with the one in my dad's Nomad. What kills 700's are heat so add a trans temp gauge and make sure the tv cable is set right.

Allan is right on the 350 parts you will want to use the 350 yoke where it slides into the trans. The 350 yoke is stronger then the 700's is. As for the drive shaft some has had to shortern theirs, mine is not short at all just new u-joints. I have about an 1" space from the tailhousing to the front of the yoke.

Some other parts you will need will be a bracket for the tv cable to slide into, a brake switch from a car that has cruise control, and if you plan on doing any towing with the car or going up and down alot of hills a switch to unlock the convertor. trans after reading the post the shaft was cut.

Link to comment
Share on other sites

I have a 700-R4 with 3.55 gears and am extrmely happy with that combination. I would recommend checking with local transmission shope (a bunch) and see if they have one on hand and price to do the conversion. I did mine about a year ago and total cost was $1,000. that included the driveshaft shortning and lockup torue converter.The only thing that I supplied was adaptor that went with the newly installed Hollly carb and the lock-up kit for the torque converter. After I got it running I bought the correct speedometer drive and driven gear and he installed it at no cost. Recommend that you might want to purchase them prior to installing the transmission. Good luck.

Link to comment
Share on other sites

Great info guys. Thanks a lot. Just talked to the shop that rebuilt my 350 turbo about 8 years ago and they said they could do the entire conversion for about 1000-1100 dollars. Music to my ears after listening to this thing roar at 70mph yesterday on I-85.

Link to comment
Share on other sites

I know that the two transmissions aren't the same length. My driveshaft had to be shortened. I have a early 80s 700R4 and it seems to work well. I'm not going to be doing a lost of cruising with mine and more than likely I'll be going to a TH400. The overdrive is good, but I've gone to far with mine and I think next year it will become a trailer queen and hauled everywhere we go. I have two drivers and the Monte will become

Link to comment
Share on other sites

Allen;

 

What do you think of powerglide?? I see alot of people running them. Seems, like the majority run powerglide. Guess it's all about the first gear, and only shifting twice. I guess that any trans can be built to hold the torque and HP. I've thought about one of those TCI w/3500 stall. It's research time.

Link to comment
Share on other sites

The PG is an awesome Race trans but there is quite a bit more work and planning that would need to be done on the drivetrain to make sure you were utilizing every bit of power you can. IE, taller gears but not too tall that you run out of motor before the traps.

The PG is a good trans for racing for two reasons, 1. they have been building race ready, trans brake equipt, heavy duty PG's for many many years so they know what to do. 2. only one shift.

 

wouldn't that be shorter gears?

Link to comment
Share on other sites

Powerglide is the same in top gear as TH350 and TH400: 1:1 ratio.

 

Choose any one of them and your trap rpms will be unchanged.

The big trick is the other gears. Powerglide works real well with a lightweight car that doesn't need a lot of gear multiplication to get it moving. I think the powerglide 1st gear is almost like starting in 2nd with a TH.

 

So the powerglide isn't missing the top gear, it's more like it's missing first gear.

Link to comment
Share on other sites

I think you're both right. The PG is not heavy car friendly and would require some low rearend gears (at least 4:56) with a steep stall of 45-5000. If Royce would still want to put some time on the street that would be a beast of a combo. For double duty but serious track I still think the 400 with about a 3500 stall is the best all around piece....Royce has the same motor I do in the Chevelle so I know it works pretty good...JMO... grin

Link to comment
Share on other sites

Glides make good drag racing transmissions most cars that make use of them are light and they spin the wee out of the motor. 52 to 5800 stall converters behind big blocks are not uncommon. Most of them have no GM parts in them including the case.

A three speed TH350 or 400 would be a better choice for you monte. 350 sucks a little less power and the rotating mass is lighter. 400's have a heavier output shaft bigger drums and clutch packs and more rotating mass to stop and start but generally last a little longer

Link to comment
Share on other sites

Robert is correct about the cruising RPM in the 1700 range with the 2:73 gears Thats what I run with a s/b 400 . I might actully dip in the high 1600 range with converter locked up . I want to change rear gears because I feel its to low of an RPM , almost lugging at times . I only use the lock up on interstate driving .

Link to comment
Share on other sites

I was driving mine over the weekend and figured out the one thing I am not use to anymore....3 spd auto's. Anyway, was searching on here and one of the places listed in the parts section. Well they recommend the 200r4. I figured down the road I would do this swap to the 4spd auto but, The 200r4 is losted as the same length as the TH350 and PG. And there are a few places that say they can be built to handle just about any HP rating. Would this be a good thought the 200r4 was thinking the 355 or 373's in the rear then. Also is there a detent to make the col shifter work with the 4spd shifting? The thought of this is new for me and was just looking to the future with her and I want her to be a driver and thought the 4spd would be a cool change. Thanks guys in advance.

 

Rick

Link to comment
Share on other sites

I'm in the process of swapping my TH350 trans for a 200-4R as well. I went with the 200-4R to avoid having to get the driveshaft shortened and what not. I was able to pick up a good core with stock torque converter from an 85 Monte SS for $50. I plan to buy a good rebuild kit and some hardened interals and hope to get it into a tranny shop this winter for a rebuild. Then I'll be able to install it and have nice overdrive performance come spring smile I'll keep you posted how things come along.

 

I'm running original 3.31 rear gears in my 70 Monte.

Link to comment
Share on other sites

700r4 is *SIX* inches longer then a 350.. not 3"

 

i had a short tail TH350c in my monte, and had to take 6" out of the driveshaft to make it all fit.

 

there are 3 different tail housings for a TH350 which is part of the confusion... they are 6, 9 and 12 inches long.. which is why you have the 6 inches, 3 inches, and same length discrepancies.

plus there is a 4x4 tail housing too smile

 

 

what's wrong with the 2500rpm @ 70mph? heck right now with my o.d not working at all, I'm doing 3300 @ 70 for an hour at a time :P~~~

Link to comment
Share on other sites

  • 2 weeks later...

I've preached till I'm blue in the face, but i'll try one last time. If you are doing a 700R4 swap stock type internals will not hold up to anything over 300HP for any length of time. By design the 700R4 is weak and doesn't have a lot of holding capacity. The good news is that there are all kinds of hardened parts out there for this tranny. There is also a lot of import junk out there as well. The sunshell is the weakest link followed by the input and output shafts. The pump drive drive isn't real strong either and doesn't have near enough vanes for a performance application. Like anything else if you wanna play, you gotta pay. If you don't pay after a series of street/strip launches with powershifts you will be picking tranny parts up off the ground. Just so you know I've had two 700R4's and the second one was built to withstand 700ftpds of torque(very expensive, but worth the piece of mind with an almost 700HP engine) JMHO. Believe who you want as most folks have their mind made up already.

Link to comment
Share on other sites

  • 2 weeks later...

Can someone refresh my memory? Which brakelight switch is used to wire an electrical torque converter lockup control through?

Seems like I remember it had two contacts sets and interchanged with a stock switch.

I converted my drive train to 700R4 and 3:55 gears and love the combo. Still trying to get a better handle on the converter lockup. Probably going to a TCI kit wired through the brakelight switch.

 

All the best,

Jabo

Link to comment
Share on other sites

  • 4 weeks later...

Do you happen to know what year, make and models used the same brake light switch as the first generation Montes? I may have more luck locating a switch from a cruise control car if there are several options.

 

Thanks,

Jabo

Link to comment
Share on other sites

just about ANYTHING GM with cruise control.

or anything GM after about 1986 up to around the mid 90's I would think.. that had a factory lock up converter.

 

my switch I'm using was a spare one for my '89 olds cutlass cierra...

 

Link to comment
Share on other sites

If it were me I'd just install a toggle switch. That way you decide when the torque converter goes into lock-up. That will save a lot of lock-up hunting making for longer converter life. It's only another 200-300rpm drop when engaged. I had this setup in the past and loved having it setup that way. You just have to remember to unlock your converter when coming to a stop light/sign, or you will chug when taking off again.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...