FD Differential Remove and Replace - Writeup

[jkstill]

Setting the backlash is what took the most time for me.

I took the measurements, determined what I thought was a good range of shim sizes to order, waited for the parts, set the backlash, and then found out I needed different shims. Lather, rinse and repeat.

Following the second round, I ordered every shim available just so I could finish this job.
(Nope, the shims are not for sale)

After a few rounds of this I got the gear pattern where I wanted it with correct backlash.

If you are assembling new parts here, be sure to torque the ring gear down on the diff. If you don't then the backlash will open up .001 - .002 after you do torque it down.

The links in an earlier installment of this include some good references for acceptable gear patterns.

One tip I do have to offer for this section is the use of the dial indicator.

When dealing in measurements that are specified to be between 0.0032 and 0.0045 you would like to make your measurements as accurately as possible. I found that it is very difficult to tell when the gear tooth touches the dial indicator without actually moving it, which will really screw up your measurements.

The solution I found was to set the dial needle to -1 or -2 thousandths. Then set the plunger next to the tooth, and turn the pinion until the ring gear tooth just touches the plunger. Turn until the needle is at zero. Holding the pinion in place then the ring gear can be moved back and forth to accurately measure the backlash.

The FSM says to measure in three places around the ring gear. I was rather anal about this, and measured and recorded every tooth. This may cause a panic until you re-read the manual where it does make some provision for variation. There were a few outliers, but nothing worth getting excited about.

In the attached pics the dial indicator is shown at 0.005 which is out of spec. Shims were adjusted to correct this. The gear pattern is shown where the pinion is too deep, along with two pics showing the final drive and coast patterns.

Now install the side seals, put some RTV on the diff sealing face, torque down the diff cover and let the RTV cure for awhile.

Next: Final assembly