Drivetrain 8.8” gear install

Chaz7795

New Member
May 2, 2023
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Hello everyone I’ve been a long time reader here but this is my first post. I’m having a very hard time installing a 3.73 gear set in my 86 mustang. I’ve been working on this for several evenings now after work and am getting no where. I’ve done machine work for about 30 years and believe I have a good grasp on how this is supposed to go, but it’s not going that way. No matter weather I have no shim or so much shim under the pinion that the pinion nose hits the carrier my contact patch is on the heel on the drive side and on the toe on the coast side. I have tried shimming the pinion in small steps and setting backlash each time, even varying backlash from .006”to .012”. Nothing moves the drive side contact patch off of the heel of the tooth. It’s a Ford Performance gear set by the way. I’ve also read up some on the face hobbed gears that there using in these rear ends.
 
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I haven't done mine yet but I've heard using the same size shims you take out gets you pretty much spot on with the Ford gear sets.
Did you measure the shims you removed? Post pics of your pattern.
 
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Thanks for the reply nick. Yeah I’ve heard the same thing, problem is some dipstick got in there before I did. I decided to put new gears in because the rear end would whine when you backed of the throttle, then when I had it on a lift I discovered the pinion bearings were loose so I assumed they were worn and that the gears would also be worn. I’ve only had the car for a few months. Some one had put a set of 3.73’s in and although the factory carrier shims were in place the pinion had too much shim under it, because when you tightened the pinion nut to take up the play it would actually lock up. Even though I don’t know the factory pinion shim thickness I figure I have already been there and everywhere around it by now. It’s really driving me nuts that I can’t get the contact patch to move off of the heel.Could there be something wrong that I’m missing? It’s almost like this rear end is impossible to shim correctly.
 
I'll be honest with you if you can get it to a shop with a good rep. It's your best bet right now.
I got a shop that turned my flywheel and balance my alum. driveshaft and they are known for off road stuff. If needed I use them.
 
I still use the crush sleeves on the ones that require them
The crush sleeve keeps pressure on the bearings as they wear in
A shim will not do that for you and will be loose after the bearings are broken in
They are designed for racing IMO where you will be inspecting the gearset regularly and re shimming it