[Leabofc54]

I have a 1986 Pontiac Parisienne with 2:73 rear gear. I want to go to a 3:73 gear but I understand I have to change entire rearend housing. I would like to know what other rearend housing will fit my car so I can have a 3:73 gear? Thanks

[Chazmac]

Your Pontiac should have a 8.5" 10 bolt differential in it. The 2.73 carrier is compatible with replacement gears. Find a differential guy and get the diff rebuilt with your new ratio. No need to replace the housing

[adrock430]

I heard that certain later model cars, like v6 blazers, have gears that will work with earlier model cars. Is this true, I have a 76 monte carlo. Thanks, Adam

[chevelle_502]

I have an 85 v6 blazer with a lim. slip 3.73 package in it. The chunk looks common, there doesnt appear to be anything special to it. Probably work in some other vehicles.

[M&M CUSTOM]

Originally Posted by adrock430

I heard that certain later model cars, like v6 blazers, have gears that will work with earlier model cars. Is this true, I have a 76 monte carlo. Thanks, Adam

You are referring to the GM 8.5 inch axle, which your Monte Carlo has.

If the Parisienne has an overdrive transmission, both you AND your car will like the change from 2.73 to 3.73.

I changed the gears in my Malibu from 2.29 to 3.73 after doing the math on what the cruising rpm's were and what they needed to be.

The mileage went from an average 13, to an average 19, but the foot in the go pedal smile factor went off the chart . My wife hates the newfound throttle response.

I would rate the difficulty level of rebuilding an axle even with rebuilding an engine, with the right tools and minimal proper coaching by someone with experience or the proper installation instructions, you can consider this a do it yourself job.

The more you tear into it, the more you need to check things that require specialized tools.

[OneMoreTime]

that car may have a 7.5 10 bolt in it and that is why the new housing is being recommended..

Check that out..the 7.5 will take a 3.73 if the carrier is changed as I remember..Now if you do need to change housings that car has a triangulated 4 bar rear with coils and finding an 8.5 that has the correct bracketry may be difficult..You may need to change to a 4 bar w/panhard to make all of this work..

Question? do you realyy want to do all of this?

Those cars typically came with a 305 sbc or a 307 olds..not a big performer..

OMT

[M&M CUSTOM]

That's right, they did happen to also come with the 7.5.

Finding an 8.5 to fit if it does indeed have the 7.5 is going to be cakework.

Your car should be a MG "B" body car, sharing parts with the Olds Delta88, Chevy Caprice/Impala, Buick Lesabre (after 84?), all Station wagons, etc.
Everything from 77 and up should interchange most of the basic parts, and the axle should be a direct swap.

Just measure to be sure.

[jimfulco]

If you need to change to a different housing, be aware that either size rear end (7.5" or 8.5") could be equipped with axles having the large OR the small wheel bolt patterns. Large being the same as 5-lug Chevy trucks & many large GM cars (5 on 5", using 1/2" studs), and small being the same as smaller GM cars (5 on 4-3/4", using 7/16" studs). Four possible combinations in all.

[Ghetto Jet]

This is my department.

In the B body passenger cars you got a 7.5" rear in unless it came with a Police or Taxi package, in which case you got an 8.5" rear equiped with 3.08 gears. All the B Body wagons came 8.5" rears but unfortunatly the wagon rears are wider, about 2 inchs wider I believe. 7.5" rears in B Bodys have 4 3/4 bolt patterns, while all wagons/taxis/police cars have 5" lug pattern.


You DO NOT need to change rear housings to run 3.73 gears. You have a 2 series carrier, and Richmond Gear makes 3.73's for 2 series carriers, as I'm sure many other companies do.

But if you plan on sending any stout amount of power through that rear I would start looking for a 77-90 Caprice with a Police or Taxi package to pull the rear from. The 8.5" rear is considerably stronger than the 7.5" and more deserving of the money you'll be spending for a gear swap.

[jimfulco]

8.5's can be found in standard cars, too. I have an '84 LeSabre 4-door with an 8.5 & the small bolt pattern. My friend has an '82 Park Avenue 2-door with the big bolt pattern. I suspect GM turned them out as fast as possible with whatever parts they had on hand, thus the inconsistency.

[Ghetto Jet]

hmm, thats good to know. I'll keep my eye out for buick sedans at the junk yard to pull 8.5"s from. I know searching under regular Caprices and Pontiacs won't yeild a 8.5". I can see why Buick, a higher end car, would be different.

[95th67cam]

I have a 84 Landau Caprice which I swapped in the entire suspension from a cop car. I have 3:42's huge disc brakes and huge drums. I also swapped the wheels with the 5" circle. I have always wondered what the mid 90's 17" SS wheels would look like on it. I'm pretty sure those are 5" circle also. The old 305 is quite a bit snapier.

[Blazin72]

Ghetto Jet, I yanked a 350 engine and trans out of an old plain jane Caprice that used to belong to my aunt (I think a 79) and it had an 8.5 10 bolt with 3.08 gears. I contemplated pulling it but never did and should have.





And I just now realized this is an OLD thread too....

[jimfulco]

Makes me wonder if I ought to keep that 8.5 when I junk the LeSabre in a couple of weeks.

I forgot to mention the '82 with the big bolt pattern has a 7.5" rear end. I think they just wanted to confuse everybody.