Cobra Rear End repair advice

DieHardChief

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Hey guys, looking for advice...

I have a leak coming from the rear end of my 01 Cobra, I dont have the resources to get it up and take a peek to see where its coming from...my best guess is pinion seal is leaking or diff cover gasket is leaking....

I set up an appt with Jaws Gear & Axle in Sacramento, supposed to be the best guys for this type of work cause they specialize and only work on rears...
I set up an appt for Monday...heres my question.

What do you guys recommend I get upgraded while the IRS is dropped? Im already paying $500 in labor because IRS needs to be somewhat disassembled, my thought is I might as well get everything I can done, while I can...my only worry is they wont go beyond rear gear and axle repair...

I know they wont do any suspension work.

Whats your thoughts, anything I should consider upgrading while I have the IRS disassembled? :beer:
 

olgreydog7

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Gears. But, without looking under there, there is no way to know what is leaking. It could be a whole in one of your cv joint boots. Seriously, go to Harbor Frieght and buy a jack and some jack stands.
 

shurur

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Sometimes a pinion seal leak can look like it's coming from somewhere else.
The pinion seal can be snugged up a quarter turn without removing everything...

Also check/tighten all diffy cover bolts..they can be gotten to without dropping anything as well.

I'd avoid shotgunning everything unless you like spending $.
 
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marcoc

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I got quoted about $1k to completely overhaul all the IRS bushings by a performance shop here in CT:eek:. I had just got my 99 at the time. I did extensive research and decided to do it myself during the cold winter season two years ago. I pieced all the needed bushings between Maximum Motorsports and Full Tilt Boogie Racing and also bought the install presses. At the same time I had differential rebuilt by a good gear shop due to worn pinion bearing from a poor 4.10 gear install from previous owner. I added an 03-04 Cobra front torque brace and a diff cover brace as well. I spent under $500 to rebuild diff and the cost to purchase the bushings. I read how-to's on here and on Full Tilt Boogies web site and its very easy if you have any mechanical know how. I would do as much as you can afford to rebuild IRS. Its worth it. Its not that the bushings are difficult to do its very time consuming. My car drives much better with the refresh.
 
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caveeagle

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...my only worry is they wont go beyond rear gear and axle repair...

I know they wont do any suspension work.

Whats your thoughts, anything I should consider upgrading while I have the IRS disassembled? :beer:

Well, they won't be doing anything significant to your IRS without doing 'some' suspension work. You have to remove quite a few components to get the diff moved.

Sometimes a pinion seal leak can look like it's coming from somewhere else.
The pinion seal can be snugged up a quarter turn without removing everything...

Do disrespect, but I don't get this comment. You don't "snug" up or tighted the pinion seal. You can tighten the pinion nut, but if the pinion seal is already leaking, I don't see this helping at all. And It would probably affect your pinion depth and screw with your gear alignment. There is a proceedure to R&R the pinion seal, counting the turns to maintain the pinion depth and not further compress the crush sleeve. I don't think this is your issue.

The rear IRS cover is notorious for being weak. The flexing of the cover causes the seal to leak. To fix this correctly, the diff needs to come out and have the rear cover re-sealed. In my case, I found the three factory rubber diff bushings were worn and very loose. You could actuall move the diff housing around with your hands.

So, you need to re-seal the rear cover, and probably replace or upgrade your diff bushings. I used Max Motorsports Poly, but would have probably gone with the FTBR kit if I had not been a little short on funds. I have heard some good comments on the "lubelocker" rear diff cover gasket, but I chose to go with the OEM seal, which is just grey silicone.

I also highly recomment upgrading the rear diff cover with either the LPW, or the FMS cover. The LPW cover was a littler cheaper and you may have to 'clearance' (grind) down the 'LPW' logo for the rear mount bracket to fit. Side-by-side, the FMS seemes a little nicer, but the LPW is nice too and a huge upgrade over the weak stock cover.
 

shurur

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Well, they won't be doing anything significant to your IRS without doing 'some' suspension work. You have to remove quite a few components to get the diff moved.

Do disrespect, but I don't get this comment. You don't "snug" up or tighted the pinion seal. You can tighten the pinion nut, but if the pinion seal is already leaking, I don't see this helping at all. And It would probably affect your pinion depth and screw with your gear alignment. There is a proceedure to R&R the pinion seal, counting the turns to maintain the pinion depth and not further compress the crush sleeve. I don't think this is your issue.

Yes I was talking about the pinion nut.....I realize that you don't turn the seal...and the pinion seal is often the problem...1/4 turn is what i wrote...I didn't say crank on it...
 
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caveeagle

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Yes I was talking about the pinion nut.....I realize that you don't turn the seal...and the pinion seal is often the problem...1/4 turn is what i wrote...I didn't say crank on it...

I think I knew what you were trying to say. But I don't think that will help much in the long run. the seal contacts the OD of the pinion yoke. Increasing the torque (or 1/4 turn... whatever) is not a reliable way to improve the pinion seal. You 'might' see an improvement just by having the rubber seal rubbing on a new surface, but it could just as easily get worse. And even a 1/4 turn on the crush sleeve will have a small impact on pinion depth. I am sure the veteran 8.8 builders could tell you exactly how much the pinion shifts with a 1/4 turn of the nut.

Anyway, sounds like the op has a rear cover seal issue anyway.
 

DieHardChief

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Im going to get it up on jacks today and peek around. Ill take some pictures so you guys can help me figure this out...

Heres what Im thinking...

Gear shop will only do gear work, but Mustang shop (Norcal Motorsports) will do almost everything I want done, except gear changes, pinion seal fix, not sure what else but anything that takes special tools or know how they defer to Jaws Gear and Axle...

so if its just a leaking diff gasket, I plan to take it to Norcal Motorsports and have them pull apart the IRS and fix the leak...while they are in there I an get the diff cover, IRS bushings, anything else that needs upgrades by them...they can handle all of the suspension work I want done.

Ill post some pictures once I get it up in the air and can take a look.

Excellent information guys, exactly what I was looking for...

Maybe I should have included a budget cause some of these upgrades are pricey for me...I have a $2K budget to get as much done as possible with priority going to the rear gear oil leak...what do you guys think?
 

shurur

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I think I knew what you were trying to say. But I don't think that will help much in the long run. the seal contacts the OD of the pinion yoke. Increasing the torque (or 1/4 turn... whatever) is not a reliable way to improve the pinion seal. You 'might' see an improvement just by having the rubber seal rubbing on a new surface, but it could just as easily get worse. And even a 1/4 turn on the crush sleeve will have a small impact on pinion depth. I am sure the veteran 8.8 builders could tell you exactly how much the pinion shifts with a 1/4 turn of the nut.

Anyway, sounds like the op has a rear cover seal issue anyway.

ok..I had the opposite problem...diffy cover bolts loose..tightened them....still leaked..still looked like the cover to me..,,,ended up being the pinion seal..admittedly, I did get the seal replaced though...and admittedly I insisted on it...

ok...well noted..at the least a small turn might find the leak overnight...but still not a good idea...bum dope on my part..


I justdidn't want to see OP going to the expense/effort of removing the diffy only to find it is the pinion seal.
 

shurur

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$2k might get you a complete new FTBR IRS with delrin bushings...

Take a look at a Detroit Tuetrac differential..
...and maybe ratech solid pinion seal??

Now i'm "helping" you spend your money..
 

caveeagle

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$2k might get you a complete new FTBR IRS with delrin bushings...

You should be able to get set up pretty well for under $2k. Do the FTBR install and replace the rear cover with LPW or FMS. If your pinion seal is ok, you should be in great shape after that! While your at it, replace the front IRS cradle mounds with 9/16" G8 bolts. This was a factory goof using the wrong size bolts. It causes cradle movement. If your having it all apart, it should be a $5 upgrade.

Take a look at a Detroit Tuetrac differential..
...and maybe ratech solid pinion seal??

Never heard of a solid pinion seal. Probly referring to the solid spacer to replace the crush sleeve. This is a non-issue unless the OP has to tear the whole diff apart again. (hopefully not). I (personally) would not use a solid pinion spacer on a street car that going to get mileage. Solid spacers are nice for race/track cars that will get pounded on and will be apart frequently. You loose longevity with a solid spacer. The OEM crush sleeve is designed to maintain a 'load' between the two tapered bearings. This will give it a little 'spring' to keep proper tension on the tapered bearings. Ratech does make a nice improved design crush sleeve (Smart sleeve). It looks to have a little more favorable crush/torque levels, so it should be easier to set up.

In any case.. without pics.. My money is on a leaking rear cover seal. Have your shop quote you a price for the FTBR bushing install and a new cover. You can have them check the wear pattern on your 4.11 gears while the cover is off. If thats ok, I would just put on the new cover, maybe replace the axle seals, and your good to go.
 

shurur

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The (ratech) pinion solid sleeve/spacer that I have, has various shims to add/remove until you get the proper torque..I never put it in though.....will check out the smart sleeve..

I'm dropping my diffy to install MM solid mounts..I did my IRS mods backwards in terms of importance.
 
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blacksheep-1

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The (ratech) pinion solid sleeve/spacer that I have, has various shims to add/remove until you get the proper torque..I never put it in though.....will check out the smart sleeve..

I'm dropping my diffy to install MM solid mounts..I did my IRS mods backwards in terms of importance.


the solid bushing (That gets rid of the crush sleeve) works so well that it was made illegal in GS racing...it would've been nice to have them legit since they solve a lot of problems.
 

shurur

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the solid bushing (That gets rid of the crush sleeve) works so well that it was made illegal in GS racing...it would've been nice to have them legit since they solve a lot of problems.

In your opinion, is there any reason not to put the solid bushing/sleeve/spacer in a DD???
Does it really wear out faster than a standard crush sleeve??
 

DieHardChief

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You should be able to get set up pretty well for under $2k. Do the FTBR install and replace the rear cover with LPW or FMS. If your pinion seal is ok, you should be in great shape after that! While your at it, replace the front IRS cradle mounds with 9/16" G8 bolts. This was a factory goof using the wrong size bolts. It causes cradle movement. If your having it all apart, it should be a $5 upgrade.

In any case.. without pics.. My money is on a leaking rear cover seal. Have your shop quote you a price for the FTBR bushing install and a new cover. You can have them check the wear pattern on your 4.11 gears while the cover is off. If thats ok, I would just put on the new cover, maybe replace the axle seals, and your good to go.

Awesome advice, exactly what i was hoping for...YOU ARE THE MAN!! :beer:
FTBR offers to kits, one that is $695 and one thats $795, which one do I buy?

Im also looking at the cover he has for sale, one is milled and one isn't, why would I want a milled one?
 

caveeagle

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Awesome advice, exactly what i was hoping for...YOU ARE THE MAN!! :beer:
FTBR offers to kits, one that is $695 and one thats $795, which one do I buy?

Not sure whats wrong with their site, but I could be even see their kits and pricing. You should give them a call.

Im also looking at the cover he has for sale, one is milled and one isn't, why would I want a milled one?

I know the LPW cover needs to be 'clearance' for the rear mount bracket to fit. They offer a solid rearmounting bracket. So I think the modified cover is either for that solid mount, or for lowerd applications. (maybe both)

On their site, I just noticed they are now selling an improved camber adjusting bolt. I had my IRS apart again, I would deffinately be planning to go this route. I have always felt 'iffy' about camber adjusters. Beefing this up would be a good idea for any car.
 

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