Differential Issue: leak and backlash?

[GokartMozart315]

so my diff is leaking, and i had to bring it to my mechanic back home, who is top notch (mainly porsche and mercedes) but unfamiliar with these cars.

he said he hasn't taken diff apart yet but sees leaking and a decent amount of backlash/driveshaft play, and wants to know what he might expect. i know our cars have a lot of driveshaft play. i have 4.10 gears in it, the steeda diff brace that came with the g-trac setup, and the ftbr delrin bushing kit installed.

what does a leaking diff usually mean, and might extra backlash be also indicative of diff problems on top of it? any thoughts/advice appreciated

 

[JBird_Cobra]

You may just need to re-seal the diff? I know quite a few of them leak over time.

 

[clbailey]

Mine has a very slow leak as well, not doing anything about it till I mod the rear end.

 

[blacksheep-1]

Some of those IRS units crack at the cover

 

[OldSVTGuy]

When I redid the seal on my pumpkin, I also replaced the stock (very soft) rubber IRS bushings with poly. The clunk was gone. At the same time, I installed a BilletFlow IRS brace. It's been almost 3 years and no more leaks.

Good luck.

 

[black4vcobra]

When I redid the seal on my pumpkin, I also replaced the stock (very soft) rubber IRS bushings with poly. The clunk was gone. At the same time, I installed a BilletFlow IRS brace. It's been almost 3 years and no more leaks.

Good luck.

I did the same thing. Poly bushings made a difference and the IRS brace provides insurance. I also added an 03 pinon brace.

OP - I had a leaking diff last summer. Turned out to be the pinion seal, so be sure to check that. Of course it, could be the cover as well. Also, Ford setup some cars a little loose from the factory, so a little backlash is expected.

 

[black4vcobra]

Here is the thread I started back then, some good info in it:

http://www.svtperformance.com/forums/new-edge-cobras-51/853713-differential-leaking-need-advice.html

 

[quick01snake]

Can you tell where the oil is leaking from exactly? There are four possibilities, pinion seal, axle seals, and cover. Mine was leaking from three of these when I bought it...

 

[GokartMozart315]

thanks for all the advice guys. i haven't gotten much chance to look at it myself, my mechanic in ny has it and will be working on it. black4vcobra and hamilton, how do you check these diff points? and do they require pumpkin removal? i had the bushings all done a few months back so that would make me a very unhappy camper...

 

[black4vcobra]

thanks for all the advice guys. i haven't gotten much chance to look at it myself, my mechanic in ny has it and will be working on it. black4vcobra and hamilton, how do you check these diff points? and do they require pumpkin removal? i had the bushings all done a few months back so that would make me a very unhappy camper...

Checking where it is leaking from is just a visual inspection. For me, I got it on a lift and I could tell the leak was from the front of the differential, hence the pinion seal. I did remove the entire differential housing, but I also added a diff brace, bushings and pinion brace and I changed the fluid in the differential, so I took off the cover and resealed with gray permatex.

If it was just the pinion seal, all you'd have to do is remove exhaust, remove driveshaft, pull pinion flange, take off pinion nut, remove/replace seal, torque down nut until bearing preload is met, replace flange, reinstall driveshaft and finally reinstall exhaust.

 

[GokartMozart315]

so the leak was just the pinion seal, but my mechanic also saw evidence of wear. there were some metal pieces on the magnetic plug, and the pinion bearings looked a little dicey. do those tend to wear out quickly, and is that indeed evidence that i need a rebuild?

 

[GokartMozart315]

ttt...also anyone know where to get cheap rebuilt diffs, if needed?

 

[quick01snake]

I know you can buy a 31 spline carbon fiber clutch ford diff for 249 new

Ford Racing Mustang rear Differential 31 Spline (86-13) M-4204-F318C at LRS - Free Shipping!

 

[shurur]

No expert here..but I think some metal shavings are expected with new gears. If the fluid hasn't been changed since the 4.10s were installed.

Also the pinion seal and bearing are the ones that take the most hits...I think those seals and maybe bearings can be replaced from under the car as stated by black4vcobra.

I'd just the change the fluid by pumping the old out..if the mechanic didn't do it already...and run it with the new pinion seal...maybe research replacing the pinion bearing yourself.

If you're going to have the diffy rebuild..$ave and get a detroit truetrak differential for an upgrade.

everything that gets opened up should be looked at as an opportunity to modify/upgrade.

 

[GokartMozart315]

wow that is a really good price, if it's the right piece, which it appears to be. brett, fluid and seal have been replaced, but gears are nowheres near new, and pretty sure fluid has been changed at least once; my mechanic seems worried bout it in conjunction with the driveshaft play. what's the improvement that the truetrac offers, and what are the downsides?

 

[quick01snake]

Yeah it's the right price, just bought one in August for mine

 

[black4vcobra]

No expert here..but I think some metal shavings are expected with new gears. If the fluid hasn't been changed since the 4.10s were installed.

Also the pinion seal and bearing are the ones that take the most hits...I think those seals and maybe bearings can be replaced from under the car as stated by black4vcobra.

I'd just the change the fluid by pumping the old out..if the mechanic didn't do it already...and run it with the new pinion seal...maybe research replacing the pinion bearing yourself.

If you're going to have the diffy rebuild..$ave and get a detroit truetrak differential for an upgrade.

everything that gets opened up should be looked at as an opportunity to modify/upgrade.

There are 2 bearings on the pinion. The external (driveshaft side) bearing can be replaced easily along with the pinion seal, but the internal bearing cannot be replaced without setting up the gears again.

wow that is a really good price, if it's the right piece, which it appears to be. brett, fluid and seal have been replaced, but gears are nowheres near new, and pretty sure fluid has been changed at least once; my mechanic seems worried bout it in conjunction with the driveshaft play. what's the improvement that the truetrac offers, and what are the downsides?

Detroit truetrac performs better, and is far more durable and reliable than stock. A quick google search shows that it is going for about $450 for a Ford 8.8. At your power level the FRPP Traction lok differential will more than suffice.