umrpunter

Hey anyone have a recommendation on a good shop to deal with to refresh my rear end and swap it from 2.xx gears to a 3.54/3.73? It's a 36. I'm doing a bushing, drive shaft, etc refresh on the old girl (160k miles) and want to do this small change to increase my smiles per mile.

Wheel Stander

If you're anywhere close to Maryland, contact Gallant's Automotive in Bel Air. They are Corvette specialists and do great work. Rob, the owner, has been working on Corvettes for over 20 years.

Zrxmax

I take it you have the 2.59 ratio currently. If you go to the 3.07 ratio I believe you will be pleasantly surprised.

I have never owned an LT-1 auto car before but have driven a few and they were very strong on the launch.

ghoastrider1

My 86 has a 307. It will set you back in the seat at starting line

Mr. Peabody

The nice thing about going from a 2.59 to a 3.07 is that you don't have to swap out the rear diff. the 3.07 was a $50.00 "performance upgrade" option.

Before I bought my 95 a dozen years ago I drove several 2.59's and 3.07's and there is a very noticeable SOTP difference in just moving up to the 3.07. Your highway mileage will suffer a little but it will be worth it.

Generally the higher numerical rear ratios of 3.45, 3.54, 3.73 etc came in the heaver duty Dana 44 that came on the manual trans cars.

I believe that the two stock ratios for the auto equipped LT1 Dana 36 were the 2.59 and the 3.07. I think that you may be able to purchase higher ring and pinion sets in the after market but those were the two ratios that came stock from the factory.

Zrxmax

No real need to go deeper than 3.07... you will be traction limited at times with 3.07s and going deeper will only make it worse unless you start doing other modifications where running the 1/4 was a top priority.

I have a ZR-1 and started with 4.10s, then went to 4.33s... what a mistake that was! I currently run 3.07s and do a lot of commuting because it is my daily driver. over 19,000 miles this year already.

I left the 3.07s in after running the 150 class in the Silver State ORR because 5th gear is 'the gear' to run those speeds with. The 3.07s while in 6th gear is like having a 7th gear for cruising.

A ZF-6 trans will not tolerate 6th gear and a lot of torque at high speeds.

psychodiagnostik

I have a 3.73 in my otherwise stock 1993, I LOVE it! It's a quantum leap over the 2.59 that was in it. It jumps off the line now (although a really nice launch is a challenge now because wheelspin) but the best thing is that the car is much more responsive at all speeds.

I wanted to do a 3.07, that's probably the easiest route, just be patient & find somebody selling a whole complete D36 diff/housing with 3.07 because there were plenty that came from the factory. However I got lucky and found a D36 that somebody already swapped in a 3.73. Probably not the best route, most recommend doing a full D44 swap with new driveshaft etc if you go 3.73. But getting into a D44 is way more expensive than just picking up a drop-in D36 with 3.07.

fredk

I had 3.54 then went to 3.73 should have stuck with the 3.54 big performance gain.

umrpunter

where did you source it?

I appreciate everyone's views on the 3.07 but I am heading the .54/.73 route. This car is a weekend cruiser and I want it to struggle for grip and accelerate like crazy on the twisty mountain roads around here.

I plan on sending in my 36 housing to somebody to put in aftermarket gears and refresh it. Anyone done this and can recommend a vendor?

fredk

Do you have a performance shop in the area.

Mike Holmen

Randy ring and pinion

https://www.ringpinion.com/DiffWizard.aspx

They have yukon gear sets for $435 for 3.54

I would buy another center section and swap the new gears into it. That way you could always have two sets of gears. Dana 36 centers are priced decent so why not.

It should take an afternoon to swap center sections out, if you ever want to go back to the old gears.

umrpunter

thank you

Polo Vert

I swapped my 2.59 D36 for a 3.07 unit from an 85. Car jumps off the line now and in my experience, highway mileage is still good at 25/26 mpg. I kept my old diff but I seriously doubt I will ever put it back in. Only real pain was having to buy a Hypertech programmer just to recalibrate the speedo. No shops around here have OBD 2 diagnostic equipment anymore and the dealer didn't want any part of it. Something to consider.

qwiketz

Anyone know how long it takes to swap a center section for a different center section? Read about it but curious how long it takes

Zrxmax

Its tedious job if you are doing it on the garage floor. I made a bracket to lift and lower the differential with a floor jack and that helps a lot.

By myself it would probably take me about 4 hours if I was in a hurry.

Tom400CFI

I would just drop the entire rear assy out, swap over parts, then put the assy back in. It's way easer to move mess with all the parts and pieces w/it out of the car, and dropping and installing the assy should only take about 1/2 hour, IMO.

383vett

I've done it both ways. It's better to drop the whole unit.

Zrxmax

Ok... I got to see this...

1. Jack up the car and position on jack stands.
2. Drop the exhaust, 6 bolts.
3. Drop the leaf spring, 6 bolts
4. Remove 8 u joint bolts... or 16 if you want the half shafts out for u joints or inspection.
5. Remove 4 bolts from drivehaft u joints.
6. Pull bolts from rear of C beam and lower trans a little bit with C beam still attached to trans while supporting the diff. ... unless you want to drop that to for some reason.

ZF Doc Beam plates make it a bit easier and definitely faster. Half hour out and half our back in... hmmm...?

Tom400CFI

Less than 5 minutes. I've posted this before.
Check.
No. Leave the spring on.
No. We're pulling the whole rear assy.
No. DS slip yoke slides out of the trans when you pull rear assy, C-beam stays in car.

5a. Remove calipers
5b. Remove trailing arm brackets from body (3 bolts each side -no nuts to hold)
5c. Remove shocks...doesn't matter from body or knuckle
5d. Remove two batwing mount bolts.
Sort of. Position stand below trans to "catch" when lowered enough. Lower rear assy using floor jack under diff. Remove rear C=beam bolts, slide diff/rear assy rearward, out of c-beam...move to left some if necessary, then drop assy to floor on jack, roll out from under rear of car.

1/2 hour out, maybe 45 min back in b/c you have to line things up which takes a little more time.

FYI, when you're removing U-joints (axle shafts and rear DS u-joint), you only need to remove ONE u-joint strap bolt, per joint. Remove one, then loosen the other bolt on the same strap, and swing that strap 180* out of the way. Then loosen the two bolts on the other cap's strap a couple turns and the joint will slip out of the yoke.


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Mr. Peabody

Be sure to let us all know what you end up doing and how you like it afterwards