Gear Moaning after 7.5" TL swap - TCCoA Forums
 
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post #1 of 5 (permalink) Old 07-29-2013, 02:41 PM Thread Starter
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Gear Moaning after 7.5" TL swap

So here's what happened:

> I swapped my factory 7.5" open diff for a ford racing trac-lok. New bearings and races as well.

> Since the install, my car likes to groan/moan/whine while coasting.

> Because of the constant groan, I have a feeling it has very little backlash, since someone told me to "eyeball it" which is terrible advice. Which would explain the stress on the ring gear and diff clutches.

Does that sound right?

> I figured it wouldn't have too much backlash since it doesn't chip/clunk the teeth of the gear.

> So I ordered the shim kit and the ford friction modifier from summit racing, hopefully this corrects it.

> I used valvoline 75W90 limited-slip when I changed the fluid, any recommendations on the best gear oil while I am at the store getting a dial indicator?

Thanks

1993 Thunderbird LX. 3.8L with Underdrive Pulleys, Ford Racing Limited-Slip Differential, Intake & Dual Exhaust, and I like to run advanced timing
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post #2 of 5 (permalink) Old 07-29-2013, 06:06 PM
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Check the pinion nut to see if it had backed off. This causes the pinion to actually move out of the proper depth under decel.
Take the driveshaft off and tighten the pinion nut to the proper pinion torque and see if it corrects the problem. If it doesn't, you need to redo it with a new crush sleeve.

Doing this kind of stuff by "eyeball" is always a bad idea. Nothing good happens when the pinion isn't set right or the crush sleeve is over-crushed.

I think you might be located close to RobertP.....he can definitely help if you need it.

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post #3 of 5 (permalink) Old 07-30-2013, 10:54 AM
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I eyeball all of mine and never have problem

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post #4 of 5 (permalink) Old 07-30-2013, 11:39 AM Thread Starter
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So, is the consensus that the backlash is too little/preload too little? It kind of sounds like a bearing, but those were replaced. The shim kit and oil are coming in from summit today.

1993 Thunderbird LX. 3.8L with Underdrive Pulleys, Ford Racing Limited-Slip Differential, Intake & Dual Exhaust, and I like to run advanced timing
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post #5 of 5 (permalink) Old 07-30-2013, 07:42 PM
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yeah, they will definitely howl a bit if you don't get that pinion depth set properly and the preload on the crushsleeve correct. i would bet its not in pattern.

either that or even from crap gears, though if yours are ford racing i doubt that.

eyeballing it, unless you've done hundreds of differentials, is a terrible idea. Ive seen some people who work at trans shops working on diffs all day long eyeball em perfect, but for me i would check everything with the proper dial indicators and things.

mine dose the same sort of noise under SUPER light throttle because i reused the old 3L27s and just tossed some new bearings/races in with the old shims, and resealed it a new pinion nut and crushsleeve.

pretty sure the 180k on the gears with worn bearings cut the pattern a bit wonky, new bearings and stuff put it all back to spec and now its not meshed perfect from the wear. the gear oil was horrible, probably not the original stuff, but close.

i plan on some 3.73's eventually anyway, when i have the extra cash for a good set.

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