[Mel Smith]

I have a ford 8" that I want to change the ring gear and pinion to a different ratio. I want to install 378 or 390 something gears and I have always been afraid to change gears because of the difficulty in getting them spaced right to not have any rear end noise. I have always changed the 3 rd member bur I have been informed that you cannot find a 3rd member with these gear ratios and I should buy the gears and install them. The gentleman told me that they had no shims to install to get the right spacing between the ring and pinion gears. Any input on whether this can be done by a shade tree mechanic without creating rear end noise will be appreciated. The rear end apparently is out of a 70 trough 72 ford according to the brake shoes that fit it.

[Notorious]

Get a good manual for a car that would have come with an 8" that covers differential teardown and rebuild. While I've never set up an 8", I've set up a good number of differentials from other cars to over the road HD trucks. The main thing you'll need besides common tools is a dial indicator and some machinist's bluing to read the contact pattern between the ring and pinion gears. It's not really particularly difficult but does take some practice to become comfortable with the procedures and paying attention to detail.
BTW, the steepest factory ratio I ever recall seeing for an 8" were 3.70s. These were in some early 60s applications, probably not an easy find these days.

[boss68]

Hey Mel,
You can set the gears up yourself if you are a very patient, quality minded person and take the time to gather all the info before hand. Shims WILL be needed as there is about a 1 in 20 chance of the case shim you now have being the one you will need.
You will need an inch lb beam type torque wrench to check the pinion bearing load and a careful hand with a very big wrench to tighten the pinion nut.
Whatever you decide, don't compromise on ANY of the settings and take your time. There are no shortcuts on this one.
I have been setting up 8 and 9 inch gears for 28 years. Let me know if i can help any further.

[leldai73]

theses are both good resources that i use a lot.


http://www.ridgenet.net/~biesiade/gearinstal.html


http://www.auburngear.com/aftermarke...structions.pdf

[gunner]

did you check on e-bay for third members

[Deuce]

Originally Posted by Mel Smith

I have a ford 8" that I want to change the ring gear and pinion to a different ratio. I want to install 378 or 390 something gears .

Unknown to many folks ... Ford did offer a 3.80 factory gear. Installed by Ford at the factory ... kind of rare ... but they did do it.

Early Falcon wagons and Rancheros is where I would look ...
Look at the rear end indentification tag ... shown below ...





The tag will tell you the gear ratio ... this one is a 2.79

GOOD LUCK ...

[Mel Smith]

Thanks for all the input that you have given on this subject. I really appreciate it. Thanks