Rear End Question

[Guest 72RustBucket]

So we finally got my Monte put up on the lift. Got the exhaust and driveshaft off, also dropped out the gas tank and took the back of the rear end off to get a look at teh gears. It's a 12 bolt, but it's not posi, and its got 2.56 gears. My goal is to make it posi, and get maybe 4.10 or 3.73 gears. I don't know a whole lot about rear ends yet, so my question is if anybody knows a place where I can get maybe a kit to get what I have to what I want. Let me know what you guys think, any input is appreciated

[Archie]

I am ordering a whole 12 bolt from Moser. They seem to be reasonably priced too.

[FerrariTruck]

Well you can put an eaton lock right in there yourself in about 2 hours all by yourself. They run about $400. I dont about the gears though

[Sam (Bones)]

setting up a ring and pinion has to be done correctly, it requires some special tools and knowledge, if you haven't done it, I would highly recommend taking it to someone who knows what they are doing.

 

I am a ex-heavy truck mechanic, I took mine to a ring and pinion shop, the pinion bearing pre-load & tooth contact pattern, pinion depth, and back-lash MUST be done right for it to last and proform correctly

[Mo's70MCs]

Sam,

 

Good advice! Minimum a dial indicator, and not everyone has one of those in their tool box. It's not rocket science, but I agree with you if you haven't done it before, I would not attempt. I'd say a takes a lil practice to get them done correctly, it's not a trial & error method. The proper mesh of gears is so important!

 

Rod

[RichG]

How are you going to use the car? If it's mostly for the street, 3.31, 3.42 or 3.55's would be your best choice. Any higher numerical gears and your rpm's are way up there, sucking $4 a gallon gas like crazy! It's been discussed here a lot and most folks that have had the 4.10's and 3.73's either drop down a few or wish they had. Folks that use the cars mainily on the strip like the higher numerical gears.

[1972mc]

I did the same. Bought a non-posi 12 bolt unit, gutted it and bought an Eaton posi unit and Richmond 373 gear set from Summit. They can answer any questions you will have re: install kit etc.., As for setting up the gears, I'm with Sam- I do all of my own work, but sent the rear to a friend that knows how to setup gear lash.

 

I did this in Jan of 07 and hopefully will know this summer how well he did!!

 

Carl

 

[kc8oye]

just call curry and buy a Ford 9" housing with the a-body suspension mounts?

 

as for installing the gears...

 

Quote:

if you've never done it, take it someone

then how would you ever learn how to do it?

 

i've not done it personally but after seeing a couple of how-to shows on how to do it, its' not that compliated, it just requires patience and attention to detail.

 

 

as for gear selection, if you aren't running o.d i'd err on the low side.. like 3.30's or similar..

 

I run 3.55's with over drive and I spin 2250 rpm @ 70mph and that's more then enough.. w/o the o.d it's a bit over 3000 iirc.

 

[502ci]

My goal is to make it posi, and get maybe 4.10 or 3.73 gears.

 

Not to beat a dead horse but a 4.10 gear will have you wishing you went lower...a 3.73 is even too high unless you don't care about mileage or plan on racing it often.

 

I have a 4.11 gear in mine and drove it for many years like that...but gas was sooo much cheaper back then. I still have the 4.11 but have an overdrive in it now to make it more bearable on the street..."my" overdrive is capable of being turned off with a push of a button and every once in awhile I turn it off at like 70 mph to see just how bad it is with the 4.11...I can almost see the gas gauge start to go down...

 

Bill

[Guest crazyirish71mc]

As stated before it all depends on your intended use of the car!

if its a daily driver, I would take Rich's advise and use 3.31 or 3.42.

[Phil]

I had a 4.11 in mine and couldn't wait to get rid of it the engine was screaming all the time, now it has a 3.42 and i like it a whole lot better. It's a street car though.

[kc8oye]

for a street car w/o over drive... I really wouldn't go higher then the 3.3x gears.

 

if you have over drive, then 3.55 is a great choice.

 

if you plan do a lot of strip time with only some street driving, then you could run 3.55's w/o o.d w/o too much trouble.

 

just my .02

 

 

[Guest 72RustBucket]

Thanks for the input guys. I really don't care about mileage much at all to be honest. Only because it's gonna be a the type of car i only drive in super nice weather/to shows. And I will be taking it to the strip when I can. And it WILL have overdrive.

 

As for the installation, my grandpa is gonig to help me with it. He is actually helping me with everything. He has a machine shop of his own... he doesn't do a whole lot anymore but he has had his own business for the last 40 or so years. He is also an undefeated pull-truck driver/builder and has had quite a few street/strip cars. as well as some strictly strip vehicles. these days he just helps my cousin with his stock car, and does random engines, trannies, rebuilds etc for his friends and stuff. So I'm fairly certain he knows what he is doing

 

 

PS- I just found a guy about 100 miles from me who has a 12 bolt posi carrier and 4.10 Richmond gears for 350$. Barely used

[Jared Richey]

I'm going with a 4:10 Gear in my rearend. No overdrive/350 Turbo Tranny, racing built.

 

I will not get over 8 hwy miles a gallon with this car and I don't care really, heck gas is so high I won't be able to drive it much anyway. Maybe gas will come back down to 2-3 bucks a gallon one day. I'd be thrilled to see 93 back to $2.50.

 

Street gear, a 3:31 is good. Sounds like your plan is similar to mine, drive it ONLY locally, and on pretty days, every once in a while sucking that 93 Octane gas at 3.75 a gallon(headed there). So I say go for a 4:10. Might as well do the Disk Brake Conversion also!

[footballubet]

as for installing the gears...

 

Quote:

if you've never done it, take it someone

then how would you ever learn how to do it?

 

i've not done it personally but after seeing a couple of how-to shows on how to do it, its' not that compliated, it just requires patience and attention to detail.

 

You are so right Tim. Not complicated at all. But very, very expensive if you don't have it set up correctly. It takes some special tools and common sense. I have rebuilt a couple (well over 100 of them) and to the best of my knowledge, they are still going strong. I like when the shade tree mechanics try to setup a diff, they usually bring it in to our shop in pieces, with their tail between their legs. Then they cry about the cost to get it right.

[Mo's70MCs]

Quote:

I like when the shade tree mechanics try to setup a diff, they usually bring it in to our shop in pieces,

 

 

Pick-up a dial indicator that's out of calibration and waste the whole Mudda-fuxxca..

 

 

Minimum Backlash Def: Minimum backlash is the minimum transverse backlash at the operating pitch circle allowable when the gear tooth with the greatest allowable functional tooth thickness is in mesh with the pinion tooth having its greatest allowable functional tooth thickness, at the tightest allowable center distance, under static conditions. What!

[footballubet]

Pick-up a dial indicator that's out of calibration and waste the whole Mudda-fuxxca..

 

 

Minimum Backlash Def: Minimum backlash is the minimum transverse backlash at the operating pitch circle allowable when the gear tooth with the greatest allowable functional tooth thickness is in mesh with the pinion tooth having its greatest allowable functional tooth thickness, at the tightest allowable center distance, under static conditions. What!

 

That's exactly what I'm talking about!

 

Clear as mud!

[7tonemonte]

Wow

I got a headache trying to figure that out.

And Scott, set me up a rear in your spare time, can I have it by june??

[footballubet]

And Scott, set me up a rear in your spare time, can I have it by june??

 

Anything for you Tony!!

[kc8oye]

lol.. yeah leo gets a few those.. 'when you can get around to it...' I need it next week.

 

[KLASSIK1]

that is the truth , Jim JD RACING from the club builds all my rearends and all my customer rearends why do it yourself when you can have a honest expert do it correctly , we all have our talents and skills and Jim is the best i have run across and he gets all my business

 

Leo

[Phil]

Jim did mine and it worked out well. Here is a link for anybody.

 

www.jdrace.com

[kc8oye]

leo.. your rear tires seem to be on fire...