So I was cleaning my garage out and I stumbled across a nifty little kit. I found brand new in the box, untouched, a 4.10 richmond gear kit. Right now I have the 7.5" rear end with the 2.73 gear in it. I don't really know too much about rear ends or gearing or any of that. What is the advantages of having a 4.10 over a 2.73 or even over a 3.73? Is a 4.10 bad without posy? Does a 1988 trans am have limited-slip difs? Thanks in advance

 

Your 2.73 will be a series 2 carrier and the 4.10 will be a series 3 so you're going to need a new posi anyway.

4.10 and 700R4 is a bad combination. With the deep first gear, you'll easily overpower the tires. 3.73 is a better choice.

 

I don't have a 700r4, i have a t400 semi auto
I'm a rear end noob, whats a series 2 carrier and series 3? All I know is I have a 7.5" rear end :\

 

The thickness of the flange where the ring gear mounts IIRC. I think a 3 series is much thicker flange than a 2 series is.

 

Ooooh, It says its a 4.10 for the 7.5" rear end but I guess you can never expect a "direct-fit". I guess i'm going to wait for a response from AlkyIROC about the transmission.

 

4.10 and a TH350 or TH400 won't be too bad. You won't like driving on the highway especially with a 26" tall tire but for stoplight to stoplight it will be fine. 4.10 gears and highway driving without an OD are more suited for trucks with 28" tall tires or taller. That's the only way to keep the rpms down at highway speeds without an OD. That's why the 700R4 is a good street tranny. You have 2.73 gears in the diff. The low first gear in the tranny helps get you off the line quicker and the OD with the highway gears brings the rpms way down on the high for better fuel economy.

The series carrier is how GM changes the diff gears. Around the low to mid 3.xx range the carrier (posi) changes. 2 series gear won't work on a 3 series carrier etc. There are aftermarket gears that allow a deep ratio such as 4.10 to fit on a 2 series carrier but OEM gears can't be swapped.

That's one of the reasons I like a 9". There's only one size carrier and gears from 2.xx to 7.xx all fit.

You have a couple of options to use those gears. Your 88 will have 26 spline axles (that's assuming you actually have a 10 bolt and not a 9 bolt). You can buy a 3 series posi for 26 spline axles, put the 4.10 gears on it and install into the diff. Spend a little more and buy a posi for 28 spline axles and upgrade the axles at the same time. Unless you have the tools and experience on setting up the gears, I recommend taking the parts to a shop that can do it and have them do the installation.

 

I know I got it about a year ago off summit and its a 4.10 gear kit for the 7.5" GM , but I don't know if it's for 3.23 and higher or if it's good on the 2.73. I don't know for sure if I have the 2.73 but I looked it up on google and it said thats what is in a 88 trans am.

 

What's the part number on the gears?

The TGO database can tell you what gears originally came in your car.

 

I'll have to check that when I get off work. And It originally was the 305 TBI with the a4 so it is a 2.73. I'll get that part number when I'm off work and I'll let you know

 

i agree. if u had a 5spd then you could do 4.10's or 4.11's however the best combo for 700r4's or automatics in general would be 3.73's or 4.56's.

4.56's really should be used for strip use. unless u dont mind goin down the local roads at 35-40mph sounding like your doing 70 or 90mph. plus the higher the gears the lower the gas mileage.

 

I have a t400, not 700r4 >.<

 

wooops my bad. but still...automatics generally do great with 3.73's. u get the picture.

 

Yeah, that sucks. I got this 4.10 but I don't think I can use it. Guess i'll try to swap it for a 3.73 or sell it and save for a new rear axle assembly.