So I have a 1986 camaro with factory 2.72 open diff and I want to go up to 3.73s. Has anyone done this swap before and is willing to share their knowledge with me? Both the factory and donor differentials have drum brakes

 

If you have a donor thirdgen rear with 3.73s and both are drums, about the only thing you might have to worry about are the threads on the brake lines. If they're the same year, it'd be a bolt-in swap. The speedometer will be off about 15-20mph. To make it read correctly, you would change one or both of the gears in the trans tail shaft. Probably have to change the "sleeve" for the driven gear too, since they're different based on tooth counts.

An 86 Z28 with a 305 could be TPI or carbed. Carb shouldn't mind a bit to have 3.73 gears. TPI would probably get a little cranky about it, since 3.73 gears will push the RPMs high enough that the engine will rev out of TPIs "sweet spot" too quickly.

 

you wont be able to put 373s in the rear end you have. I tried. the housing is too small. you will need a completely new rear end. I have a 305, 700r4, 273 open rear end and the shop said the largest gears that will fit that housing is 308s. I wasn't going to pay $600 for 308s so I left it 273s for now. I used an rpm calculator and I decided 355s are better.

 

It's not the housing that's the problem with a higher gear ratio, it's the carrier. The actual differential that the ring gear bolts to. 3.08 and down use one size carrier, and up use a different one. They make higher gears that will bolt to a 2-series carrier, but it doesn't really matter if the entire axle assembly is being changed.

 

Either they didn't know what they were talking about or you misunderstood them. The housing is the same for all gear ratios. Like Drew said, the differential is the only difference. The 2 series is for 3.08 to 2.41 gears and the 3 series is for 3.23 to 4.56 gears. All you have to do is use the right series differential for the gear ratio that you want to use, or get the special thick 3 series gears that fit the 2 series differential.

 

Did the exact same swap. Except I swapped the whole rear end out being it was a very low mileage piece. Both were drum brake it was a quick easy swap. My speedo is way off now and I have a VSS and buffer box to deal with on the 89 which is why I haven't changed it. Yours wont be bad you have the cable speedo you only have to change the speedo gears to correct yours. I have the correct speedo- drive gears if you want to go through with that later id be willing to let them go for what I have in them.

 

The VSS is still run off a drive/driven gear combo. There are a couple different sensors, but aside from the electronic VSS for the T5, they seem to be available. Just a matter of following the chart in the Parts and Illustrations catalog. The right sensor, plus the right drive/driven gears, and the speedometer will read correctly.

When you go outside of the factory supported gear ratios, it's still just a matter of having the correct drive/driven gears. There are online calculators for figuring the number of teeth needed.

 

I have an auburn posi unit somewhere in the garage I can sell ya. Used it when I put 3.73's in my 86 back in the day. If you go to 3.73 on a tuned port motor you should at least upgrade the top half of the intake to get a little more rpm tho.

 

if you go to richmond gears website they make the 373 that fits in the #2 carriers now no need to switch the diff https://www.richmondgear.com/wp-cont...n1.pdf#page=27

 

Thanks for the input guys! I forgot to mention that the donor diff is a factory posi with 2.72s as well

 

The factory limited slip slip differential will be an Auburn. There is a good chance that it is already worn out or close to it. If you want to give it a try then you can get the thick gears that fit the 2 series Auburn. If you don't want to take a chance on the Auburn then I'd recommend a complete kit with a new 3 series LSD, new gears and a USA Standard installation kit from Quick Performance. http://www.quickperformance.com/GM-7...t_p_20409.html

 

I figured its about as worn out as mine or more. I am very limited on funds so i dont think I'll be able to buy a new diff. I'll probably take a chance with the 2 series. Thanks for the link to the parts!

 

How much money do you have in those speedo drive gears? I might take you up on that offer

 

Never throw good money after bad. If you can't afford to do something right, find a way to save the money and do it later.

3.73 gears with a worn out differential will make for a smoky passenger's rear tire. But if you're not getting traction, you're just burning rubber. Might just as well get a peg leg 6cyl rear and run it as is.

 

the shop did say carrier not housing was the issue.

 

https://www.thirdgen.org/forums/transmissions-drivetrain/750865-hesitation-4-10-gears.html

 

Whos set for summer?

 

DMCCAIN, Hi, would you by chance have the part #'s or details for the drive and driven gears you bought? I'm trying to come up with the right 2 gears with 3:73 gears and it's a little confusing.
Thanks