bop 8.5 3.73 gears

[1971olds350]

i have a 1971 cutlass with a 8.5 10 bolt bop with 2.73 gears and i want to change over to 3.73's how do i do it..

[monzaz]

Ok well if your not familiar with gear swaps and set-ups probably best to leave to a shop that is. BUT if you have alot of time and can follow instructions I can always help you.

First you would need the 3.73 gears. In the corp 8.5 rear 1971 -1972 the 3 series carrier breaks are 2.73 -5.57 so your 3.73 will bolt right up to the exsisting carrier unit (posi or standard open one wheel peel unit)

Pinion depth could change for proper mesh of the ring and pinion so that must be taken into consideration. Bearing puller will be needed, pry bar of some sort for removal of the carrier, dial indicator with magnetic base for checking backlash setting(29.99 at habor freight will work fine) selection of pinion and carrier shims (usually a good time to change all the bearings and the complete rebuild kits have everything to set a ring and pinion plus posi / open unit up completely, we sell them for 89.00)

A good COMPLETE kit will include the following
-pinion inner and outer bearings and races
-carrier driver side and passenger side bearing and races
-pinion seal
-pinion crush sleeve
-pinion nut
-inspection cover gasket
-carrier shims
-pinion shims
-ring gear bolts
-marking compound and application brush
-lock tight for the ring gear bolts
mega add on kits will include the axle bearings and seals and vary in price depending on the bearings used ex. press on bearing usually more expensive than the c-clip type axle bearing systems.

I you need step by step help look to my site that specializes in just GM differentials. I can help walk you through the set up process if you are willing to spend the time. PLUS you may help many other people with the same troubles you might expereince. Jim

www.jdrace.com

[gearheads78]

Good source for cheap used GM 3.73 gears is late model GM trucks and SUVs. They still use the same 8.5 sized ring and pinion. Purchased mine for $90.00 already pulled. You could propably get for less if you are willing to pull yourself in a yard. Look for axle code GT4 in the glove box.

-Richard

[1971olds350]

Originally Posted by monzaz

Ok well if your not familiar with gear swaps and set-ups probably best to leave to a shop that is. BUT if you have alot of time and can follow instructions I can always help you.

First you would need the 3.73 gears. In the corp 8.5 rear 1971 -1972 the 3 series carrier breaks are 2.73 -5.57 so your 3.73 will bolt right up to the exsisting carrier unit (posi or standard open one wheel peel unit)

Pinion depth could change for proper mesh of the ring and pinion so that must be taken into consideration. Bearing puller will be needed, pry bar of some sort for removal of the carrier, dial indicator with magnetic base for checking backlash setting(29.99 at habor freight will work fine) selection of pinion and carrier shims (usually a good time to change all the bearings and the complete rebuild kits have everything to set a ring and pinion plus posi / open unit up completely, we sell them for 89.00)

A good COMPLETE kit will include the following
-pinion inner and outer bearings and races
-carrier driver side and passenger side bearing and races
-pinion seal
-pinion crush sleeve
-pinion nut
-inspection cover gasket
-carrier shims
-pinion shims
-ring gear bolts
-marking compound and application brush
-lock tight for the ring gear bolts
mega add on kits will include the axle bearings and seals and vary in price depending on the bearings used ex. press on bearing usually more expensive than the c-clip type axle bearing systems.

I you need step by step help look to my site that specializes in just GM differentials. I can help walk you through the set up process if you are willing to spend the time. PLUS you may help many other people with the same troubles you might expereince. Jim

www.jdrace.com

how much does it cost to swap to posi and 3.73 gears parts and labor included

[gearheads78]

have 900.00 in mine not including the powdercoating. Thats new eaton posi, gear set up, new bearings and the used gears mentioned above

[74 Omega]

I got mine out of a 79 Trans Am. I bought the whole rear end for $250. I had to take the guts out cause the rear was just a bit wider than mine. I thought it was easier to swap the guts than weld new perches and redo the brakes. I reused my axels they were both 28 splines. With the price of the Trans Am rear, new axel bearings, all the oil, gaskets, etc I might have $300 in it. Good time to do brakes as well. BTW it was a bitch getting the speedo back to normal(it was reading at least 20mph over). I just had a complete tranny overhaul they did it for me while it was being rebuilt. The good new is now I have 3.73 gears and a TH350 tranny built to take 350 to 400 HP This winter it's engine time

[citcapp]

Monzoz,

Just finished my 455 swap into my 57 Olds. Awsome except for the single wheel traction. The Olds rear end is tough I have been told and can handle my HP and torque. Is there a Posi available for this rear end? I have the tools and know how to install.

Thanks in advance

[monzaz]

Just PM me and I wil lprice you out some parts then you can compare with others ...I will get you a number to call and we can discuss all what you think you need. Jim - J D Race.com