Shim Kit for 3.73 gears. Necessary?

91BLOWNSC

Registered User
Well I was about to make a purchase on a set of 3.73 gears through a local company. And on there website they have all hte gear levels listed and at the bottom there is a "shim kit" available for 99 dollars. I called and they informed me it comes with the shims, 2 pinion bearings(??), grease and maybe a fourth item but I have drawn a blank. I asked them if it was necessay for the installation of the 3.73 gears and he said sometimes it is and sometimes it isn't depending on the condition of my current bearings and rear-end. Basically my question is it necessary? What is the typical shape of a rear-end with 132k. Can I get buy without this kit? It seems no one usually mentions it when I see someone installing gears.

Any info you can provide would be helpful!! Thanks.
 
This article will give you some background on an 8.8 gear install:

http://www.corral.net/tech/drivetrain/gears.html


At that mileage on your diff you may want to look at installing new bearings and seals. The clutch pack may also need rebuilding. This is not an impossible DIY job, but you do some some special tools to get it all setup right. Most people take it somewhere to have gears installed. A competent shop will replace parts as needed. Many places do sell kits of the parts needed.
 
Thanks.

That was a very helpful artical. But a few things I am unsure of are the speedogear. Where exactly is that installed at (can it be installed after the new ring and pinion are installed?)?

And my gears are being professionally installed. Its a friend and he is installing them free of charge. So I want to to be the least amount of hassle on him as possible. I do have the bring the rear-end to him though. How long usually is the removal process of the rear-end?

I guess I could always give it to him, let him tear it down and he could always let me know if I needed any new parts. Thanks for the reply also.


Oh btw George, how are the 3.55's that you have installed compared to the 3.27's that came with the car. Are you statisfied, or do you wish you would have tried the 3.73s? I could be swayed before my purchase :eek:


Also, I have already asked a few people about this who have helped me out with this info, i would also like to get a majority of people to chime in. Can this be considered typical MPH to RPM readings for an early model auto with 3.73s?

45mph == 1421 rpm
60mph == 1895 rpm
75mph == 2369 rpm
85mph == 2685 rpm

I used a conversion website to do this. Are these usually accurate? I have stock tire sizes.
 
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Excellent Calculator:

Gear Calculator

PS. Final drive ratio on an AOD in 4th gear is .67:1, so you will want to enter .67 in the last colum. 3rd gear is 1:1, so you can figure it also without it being in OD.

Thomas
 
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The speedo gear is not a problem. It is a plastic gear the tailshaft of the tranny and is easy to replace. We have a speedo gear calculator on the main site.

I am happy with the 3.55s, but I also went with the wide ratio gears in my AOD (2.84 wider ratio first as opposed to 2.40 first gear in the AOD). I believe this combo is a little higer numerically than 3.73s with the AOD. It has enough torque to smoke 'em longer than I can afford tires. (The motor is not exactly stock.)
 
Alrighty..

Ok thanks guys.

Thomas, can those conversions be deemed accurate then? Is that the rpm that my car will run at? Why doesn't the conversion need to take into account my transmission ratio such as the 2.40 and 2.84 that george mentioned. It seems a value such as that would need to be entered. And it seems that everytime I ask someone there rpm at a given speed with the 3.73's it seems to be higher than the numbers the conversion page is spitting out. Maybe Im just dumb, I dunno.


George, Im also assuming your car isn't a daily driver? Or is it? I just ask because then you have probably did some freeway driving with them.


I usually cruise quiet "briskly" you could say in my t-bird and I love it. I just didn't want to cruise "briskly" now and have to hear my engine churning at 3-4k. Know what I mean?

Thanks for all your help guys!! Is appreciated.
 
i installed 3.73 in my 91 sc and the calculator told me i needed a 23 tooth gear.well i noticed when i was going speed limit i was flying by cars,anyhoot g/f got speeding ticket so i took it to shop and they calibrated it to be 7 mph off at 60.when speedometer said i was doing 60 real speed was 67 mph.so i really needed 21 tooth gear with stock 16" tires.so be aware
 
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