Rear Diff caught fire...

[ddavisaf]

I'm not where near this car right now, so I cannot look at it. I'll give you the info that was given to me and together we can figure everything out .

1995 Eagle Talon TSI, 6 bolt swap, 95 AWD drivetrain.
110 mph for about 1 1/2 hours near constant.
Noticed a burning smell, smelled like rubber.
Pulled over, checked the engine bay good, checked the underbody good, went to the back of the car and saw his rear diff on fire. Threw some water on it and called me.
At this time I asked him if he heard any kind of grinding or whining sounds before he pulled over. He said no. I told him to put the car in neutral and try and push it forward by hand. It rolled just fine. So, the rear diff isn't locked up.
He limped it to the next exit's gas station. Jacked up the car and climbed underneath. Inspected the exhaust hangers and diff mounts. The smell of burning rubber was alot more noticeable the closer to the problem area (Go figure right?). He then said that it looked like rubber was dripping onto the top of the diff. He finished driving it to wherever he was going. The next morning he calls me to tell me his diff is now leaking a small amount of fluid. So, here's where I'm at now.
I'm thinking he has to replace all the exhaust hangers and diff mounts. Also the inlet seal on the diff will have to be replaced along with the axle seals. My question is, as long as it's not making any problematic sounds, the diff is good correct?

 

[wolf20043]

I'm not where near this car right now, so I cannot look at it. I'll give you the info that was given to me and together we can figure everything out .

1995 Eagle Talon TSI, 6 bolt swap, 95 AWD drivetrain.
110 mph for about 1 1/2 hours near constant.
Noticed a burning smell, smelled like rubber.
Pulled over, checked the engine bay good, checked the underbody good, went to the back of the car and saw his rear diff on fire. Threw some water on it and called me.
At this time I asked him if he heard any kind of grinding or whining sounds before he pulled over. He said no. I told him to put the car in neutral and try and push it forward by hand. It rolled just fine. So, the rear diff isn't locked up.
He limped it to the next exit's gas station. Jacked up the car and climbed underneath. Inspected the exhaust hangers and diff mounts. The smell of burning rubber was alot more noticeable the closer to the problem area (Go figure right?). He then said that it looked like rubber was dripping onto the top of the diff. He finished driving it to wherever he was going. The next morning he calls me to tell me his diff is now leaking a small amount of fluid. So, here's where I'm at now.
I'm thinking he has to replace all the exhaust hangers and diff mounts. Also the inlet seal on the diff will have to be replaced along with the axle seals. My question is, as long as it's not making any problematic sounds, the diff is good correct?

I would give it a try. It sounds like the smell was from the fire melting the rubber boots on the hangers. But He really should find out where and why the fire started after changing everything.
Mike

 

[ddavisaf]

Nothing was changed before the fire.
I just need to figure out if I need to replace the entire diff or just the seals.
We have to drive this car 1900 miles in a week and we don't want to break down on our way there, and we don't want it to break down on the guy after we drop it off to him. He's good people.

 

[wolf20043]

Nothing was changed before the fire.
I just need to figure out if I need to replace the entire diff or just the seals.
We have to drive this car 1900 miles in a week and we don't want to break down on our way there, and we don't want it to break down on the guy after we drop it off to him. He's good people.

Makes alot of sense. Does it still drive ok after the fire? I would check EVERYTHING while you are under there, make sure no shavings and chit in the gear oil and as you said, no sounds that should not be there.
Mike

 

[DSM90AWD]

Was the exhaust making contact with the rubber exhaust hangers/undercoating?

Back in my childhood days I used to light the palstic 6-pack binders on fire to burn ants. Would drip flaming molten plastic on the lil buggers. I'm thinking the same thing happened here (replacing ants with a differential).

I'd say the diff is fine internally, but shoudl replace any of the external seals/CV Boots that may have been damaged. Also, for peace of mind, I'd have him drain/replace the differential fluid and put in some synthetic

 

[ddavisaf]

Was the exhaust making contact with the rubber exhaust hangers/undercoating?

I'm not sure but that was my initial thought. However once he mentioned leaking fluid from the diff I started to get a little more concerned.

Back in my childhood days I used to light the palstic 6-pack binders on fire to burn ants. Would drip flaming molten plastic on the lil buggers. I'm thinking the same thing happened here (replacing ants with a differential).

I'd rather replace the differential with the ants actually... it'd be alot cheaper to fix.

I'd say the diff is fine, but for peace of mind, I'd have him drain/replace the differential fluid and put in some synthetic

Would you say that the fire that damaged the diff and caused the leaking could simply be the inlet seal for the driveshaft?

 

[jtmcinder]

Check both rear axles.

If a rear axle breaks, the rear VC will try to maintain a lock. But asking a VC to re-route significant amounts of torque for an extended period is asking too much. It could have been locking, releasing, locking, releasing, the entire time, getting more and more pissed off at the driver through-out.

Note that, if I'm correct, then the center VC may also have taken a hit. During those times that the rear was unlocked, the center would lock.

- Jtoby

 

[ddavisaf]

That's what I was afraid of. Thank ya.

 

[DSM90AWD]

Would you say that the fire that damaged the diff and caused the leaking could simply be the inlet seal for the driveshaft?

Lookign at a pic of my old DIFF and knowing the proximity where the exhaust passes under the it, I'm thinking of a different scenario. The diff could have been leaking already from the pinion seal (onto the exhaust pipe) and the exhaust just ignighted it causing other things (exhaust hangers/undercoating) to smolder.

FYI.. on my 1G the exhaust goes under the diff and then parrallel, so don't see how molten rubber hangers could drip on top of it

Would be cool if he could post up some pics

 

[ddavisaf]

I agree. I'm going to go pick him up today and take some snap shots. I told him to smell the fluid and what he described smelled nothing like diff fluid so I'm not even sure it's leaking from the diff....

 

[DSM90AWD]

If a rear axle breaks, the rear VC will try to maintain a lock

FYI.. when my rear 3-bolt axle went, my car would barely move. I tried to drive back home from the track (yes naive was I back then ) and car would only go ~25mph (any more power and the diff would slip) for ~1/4mile at a time before my rear would heat up no power would be delivered to the wheels. Kept having to "rest/repeat" to get to my friends house 1 mile away. Yes my center diff fried during this whole "learning experience"

So to get up to 110MPH for any amount of time seems pretty odd to me if an axle went

 

[tux2122]

the axles and their boots were untouched...they also appeared to be brand new. I got under the car and felt everywhere I could...nothing was on top of the diff so I don't think anything leaked on top. It looked like something may have leaked onto the side and their was a tiny bit of some fluid where the driveshaft meets the rear diff. It has the consistency of grease to be honest and it smelled like crapped up rubber. Im not sure what differential fluid is supposed to smell like so I couldn't tell you. I tried moving the driveshaft around with just my hand and that didn't budge...their felt like some big ass rubber puck that sits between the rear and the drivesahft and to my surprise that felt and looked ok.

 

[DSM90AWD]

As an FYI.. Differential fluid is 90W Gear oil so resembles a relatively thick oil. The Rearmost driveshaft U-Joint is pumped full of grease so may be the residue you saw on the Diff? Also the axles CV joints are full of grease, so when they crack (and they will), they will sling axle grease all over the underside of the car/wheels

 

[jtmcinder]

So to get up to 110MPH for any amount of time seems pretty odd to me if an axle went

Yes, this would be an impressive feat for a rear VC, but it is still possible. Note that many drag-racers have finished a run as a RWD with all of the power going through the center VC after blowing up a center diff. And some of these runs have had traps well over 100 mph.

- Jtoby

 

[jtmcinder]

what he described smelled nothing like diff fluid so I'm not even sure it's leaking from the diff....

Inside the VC is a silicone fluid. Very different from petroleum-based stuff around the gears in the diff.

- Jtoby

 

[tux2122]

the whole point of this is that I took the car to a shop to get looked at and I just want to make sure I don't get screwed. I don't want to buy a whole diff if all I really need is say an inlet seal and to change the fluid. But at the same time I also want to make sure I didn't blow something else besides the diff because this is bumf%^& ND we are talking and shops around here know jack sh&t about DSM's. So...any other ideas or possibilities?

 

[jtmcinder]

You know, it's hard to keep up when you switch accounts. I ignored your last post, because I assumed it was a thread-jacker. Maybe I should have noticed the location was the same....

Have you taken off the drain plug to see if the diff is down on fluid? If the diff is still full and none of the boots are ripped and/or missing grease, then you need to look farther afield for the source of the burning material.

Are you sure that no splines are stripped? Have you raised the rear wheels one at a time (with the car in gear and the parking brake off) and made sure that neither would turn?

- Jtoby

 

[ddavisaf]

tux is the owner of the vehicle.
I'm.. well me. He just jumped in after he saw I had made the thread.

 

[ddavisaf]

Update: Tux took the car to a mechanic where he's at right now and had everything inspected. It seems that the only issues are with the pinion seal and the bearing. If there is any internal damage to the diff he'll find out on Wednesday. We'll keep y'all updated.

 

[Old Mitsu Tech]

110 mph for 1.5 hours? Where are the Highway Patrols? . I almost couldn't think after reading that part. I could only see ticket books and judges. If this helps, I would use a no contact digital pyrometer and after a test run I would check temps from axle to axle. If the differential is the hot spot and it's a limited slip, as was suggested before jack up one side and with trans in gear try to turn wheel to see if it turns or not. If it does, you are definitely going into the differential. Good Luck

 

[ddavisaf]

The car's a mutt. We *think* it's a LSD. It's got the sticker. However the rear diff was replaced and we're not sure with what year diff. The car has a 99 transmission in it and we thinks 95 everything else..... soo... go figure. The situation is becoming very confusing very quickly due to so many variables.

 

[ddavisaf]

Alright, Update:
Pinion seal has been replaced. No more leaking diff.
Here's the new problem. When the diff was opened up to replace the seal the mechanic said there was a ton of metal flakes/chunks. He said the magnet that was supposed to be attched to the drain plug has dislodged it'self and was running rampant in the diff.
He said the U-Joint wasn't.... Bad... but it looked rough.

Now the diff is making a loud whine when there is little to no load applied to the throttle. While accellerating there is no abnormal sound or operation.

Is this LSD salvagable? Or are we going to need to replace the entire diff?

 

[DSM90AWD]

Now the diff is making a loud whine when there is little to no load applied to the throttle. While accellerating there is no abnormal sound or operation

I dont' have my book in front of me but remember there being specific pinion preload specs which might not have been followed I assume it was not this way prior to the new seal?

Just an FYI (since I looked into this myself), the labor of rebuilding a rear diff far exceeds the cost of just picking up a used one. The cost of an LSD in itself (minus the labor to install) is ~$1K)