Rear end gears needing rebuild at 50k?

[Midlife Crises]

My first guess is those gears are set up too tight. The gear mesh whine rises and lowers with speed, under load or coasting.

 

[BadPiggy]

DAMN!
That sounds horrible!

 

[Geosh]

Well they fixed it, or rather had the neighboring shop fix it for them. Had to put in a new set of gears because the last ones were trashed.

Never again am I taking my car to a shop for anything I can learn to do myself. Took 28 days for a rear gear install, got a new differential I most likely didn’t need, and they curbed one of my new GT500 wheels.

Glad it’s done but what a crap show.

 

[Juice]

Im glad you got it resolved, but damn. They are responsible for body and wheel damage.
[QUOTE
="tjm73, post: 2467505, member: 6368"]Ford has installed millions of 3.73 and 4.10 gears in Rangers for decades, plus F150's and other trucks and cars. They don't whine. Every time I see someone with noisy gears, I know it's the install 95-99% of the time.

The 8.8 seems to be sensitive to install tolerances.[/QUOTE]

Funny, IMO, I think the 8.8 is pretty easy to 'get right'. I swapped the gears in my 91 many times. My gear progression was: 3.73 - 3.55 - 3.27 - 3.08 - 3.27. And original gears were 2.73.
3.73s were good N/A. Then the blower went on.
Anyway, the original pinion shim was just used in all.

I would like to know what really happened with this.

 

[1950StangJump$]

OP, take a look at my craziness. This wasn't my first challenge loud gear whine either.

https://www.s197forum.com/threads/calling-any-rear-end-gear-install-experts.137529/

 

[rocky61201]

[/QUOTE]Anyway, the original pinion shim was just used in all. [/QUOTE]

I've swapped gears I think 3 times now and always swapped over the original pinion shim. All FRPP 3.55's except for my last set. I went with SR performance 3.73 because they were on sale and I was probably in a budget crunch at the time. This set lasted only a few months. Still drivable but plenty of noise. Changing back to FRPP 3.55's right now. I didn't measure or mic it but visually I would swear the lip on the SR performance pinion that the shim and bearing sit on was a little bit higher than what I saw on my FRPP pinion. I didn't have a chance to compare side by side because my machine shop already popped the old bearing off and moved the shim and pressed on the new bearing on the FRPP pinion. But my wear pattern on that SR performance pinion was a little too deep. I guess I should not have taken for granted that you can always just simply swap over original pinion shim.

I'm not bashing SR performance, just saying I should have taken the extra step to measure pinion depth on that install.

 

[Juice]

Just to clarify, just moving the original shim is by no means the correct way to swap gears. It is a shortcut that saves time doing the job and works well MOST of the time. But not always.
The pinion shim is there for adjusting for case/housing machining tolerances. You add or subtract the scribed number on the new pinion and old pinion. If you want it to be dead on. I personally find that a few thousands plus or minus from ideal pinion depth causes no issues. As long as the tooth contact pattern and backlash can be set by shimming the carrier.

This approach has worked for me.

 

[Norm Peterson]

Just to clarify, just moving the original shim is by no means the correct way to swap gears. It is a shortcut that saves time doing the job and works well MOST of the time. But not always.
The pinion shim is there for adjusting for case/housing machining tolerances. You add or subtract the scribed number on the new pinion and old pinion. If you want it to be dead on. I personally find that a few thousands plus or minus from ideal pinion depth causes no issues. As long as the tooth contact pattern and backlash can be set by shimming the carrier.

This approach has worked for me.

Sounds about right.

I bet that something like 0.040" difference in pinion depth would be well outside ±a few thousandths, though.


Norm

 

[Juice]

All 8.8 gears I have done, the pinion shim was .022-.028".

 

[Rick Simons]

To quote my Dad: "Check everything, assume nothing!"