Gen II Differential Overheat

[SmokinViperGTS]

After running about 15 runs on the Vegas auto-x course this spring, stopping for lunch, and then hitting the road course for a couple of 20 minute sessions, my differential overheated to the point that I was blowing 140 weight past the seals and all over the underside of my car. Made for a stimulating blue cloud following me around the track, until I got black flagged. Thought it was some other problem, and got that fixed, but continued to have the problem on my next drive (easy highway cruise), until I finally found the problem. That's when I was told that the Gen I's and II's have a weak diff that commonly overheats on the track. It you don't monitor it (how?) and let it cool, you blow a seal and get to see your favorite mechanic again.

But I was also told that Dodge has a kit cooler specifically for this, and found it in the Mopar Street Essentials catalog - part #P5007010. It requires me to either drill and tap my diff case for the fluid lines, or replace some portion of the case with a newer Mopar part (that I haven't found yet) that has the ports built-in.

So, now I'm wondering if anyone else is using this kit, or something else, to solve this problem? What sort of experience are you having with your solution? What did the kit cost - I've heard it's quite expensive? Who carries it?

Thanks,
Steve

DIFFERENTIAL COOLER SYSTEM
Designed to keep your differential cool under
race conditions.
• Recommended for use on 1996–02
Vipers used at racetrack events
• Temperature switch automatically
activates pump and fan at elevated
temperatures
• Production housing requires drilling
and tapping for fittings
• Differential disassembly recommended
• Mopar Performance differential housing P5007441 and
differential assemblies P5007401, P5007402, and P5007403 are
pre-drilled and tapped
Kit includes:
• Electric pump
• Air-to-oil heat exchanger
• Electric fan
• Required hoses and fittings
• Wiring harness with factory connectors — no splicing
• Temperature switch and relay
• Templates and instructions on compact discs included
P5007010 1996–02 RT/10 and GTS Differential Cooler System

 

[Leslie]

ditto, had the same thing happen to me last wknd at the track.

 

[Tom F&L GoR]

I have a Gen 1 with one of those "weak" differentials that I purchased at 20,000 miles and now have ~95,000 miles. Over the 11 years of ownership I've changed fluid twice; sort of soon after I bought it and sort of at 60,000ish miles. I autocrossed for many years, moved on to 3+ years of track days. Many long (3-5 hour) trips. Never changed the diff fluid based on severity, only total miles.

Each change was with the Mopar fluid. I only recently (two-three months?) added a NACA duct from the trailing edge of the transmission belly pan directed at the differential because I went from the Gen 1 side pipes to the Gen 2 rear exhaust.

Gear oil doesn't "boil" when it gets hot. It will smell like sulfur, the active chemistry to protect the surface. If the fluid is trying to escape, it also makes me wonder if the original fill level was too high and it was getting foamy.

I would like to hear more about the "commonly" overheated diff. At the track days, Viper track days, Viper AX events, I don't think the topic ever came up. Your experience seems unusual. Maybe we need to divide this into Gen 1 vs. Gen 2 due to the exhaust?

One of the bolts in the case is able to be drilled through. It makes for a small drain hole and takes long to empty but the bolt acts as a plug. You don't have to drill and tap a thin spot to add a drain.

 

[FrankBarba]

i owned a 95 that all it ever saw was Heavy Track Duty - along with alot of Hard WTW Racing. I changed fluids regularly. I never had an issue. I believe that if you change your fluids on a regular basis you will not have alot of issues.

 

[SmokinViperGTS]

Tom, You're waaaaay more tech savy on Vipers than I am. In fact, while I'm perfectly happy to take a wrench to any part of my 39' boat, I don't touch my snake with one - I leave that to guys that know what they're doing. That's because I don't go 150mph in my boat.

So, when one of them changes out my gears (got 3.55's) and installs fresh fluid, and then I have a problem on my very next track day, I just ask questions. In this case, another one of those guys diagnosed/fixed the problem, told me that he didn't think it was related to the recent gear change - from what he could see, and went on to describe the "weak" diff problem.

The interesting part is the factory kit designed and "recommended" to fix the problem, and the newer housing that comes with 3 holes pre-tapped and plugged to support it. Doesn't that implicitly suggest that there IS a problem?

Like I said, I don't know anything but what I'm told - so I'm out asking questions again, to see what experiences other folks are having with this. I'm hoping that this thread will bring out other folks that have had "the problem", and find out what they did to fix it.

And hopefully, find a happy solution other than a permanent repeating entry on my mechanics' appointment book.

 

[dave6666]

So, when one of them changes out my gears (got 3.55's) and installs fresh fluid, and then I have a problem on my very next track day...

What is the time frame between gear install and track day?

 

[ViperTony]

Hmm...if there's a problem with the diffs, the Wizard would know for sure. After all, if the diff is weak then he must've seen quite a few of them in his shop considering what some of our local member's put their diffs through. Why not give the Wizard a call and confirm what your mechanic told you?

 

[SmokinViperGTS]

ViperTony - that's a great thought! I'll do that tomorrow.

Dave666 - A couple of days, and 0 miles. I trailered the 1200 miles to the track. Car has 38k miles, and I'm pretty sure this was the first fluid change for the diff. Not sure if that makes a difference.

Don't get me wrong, I'll be delighted if this was just a strange one-time thing. I've heard that the factory cooler is $3k plus install, which I'd rather use on tires and fuel.

Steve

 

[Dan Cragin]

I have seen this issue many times over the years. First off, new gears will run hot and overheat unless broken in properly. The fluid gets hot and thins out, the seals deform and fluid leaks. When everything cools down, most likely the leaks will stop. If your posi-unit has weak clutches this will contribute to overheating.

If the fluid overheats it wont do it's job and problems continue. If you track your car without a differential cooler, check the condition of your fluid every couple events.

Coolers are really only needed on track cars. Do not use the Mopar cooler, trust me.

There are many other variables to differential heat. Give me a call and I can give you advice. No sales, just advice.

 

[SmokinViperGTS]

Dan - thanks, I'll give you a call in the morning.

Steve

 

[Bugeater]

My car was bought off showroom floor in 96. Been a track car all its life. No cooler. Change fluids once a year tho...

 

[Tom F&L GoR]

I'm very curious as well, and tend to look for the weak link before applying a large hammer.
Did the fluid smell? If no sulfur smell, it is not really being stressed.
Gear oils are developed using some pretty hefty high temperatures and of course, getting thin when hot should be expected.
What is a break-in procedure for rear gears?
Weak clutches would allow one wheel spin, but if on a track event would this really matter?
Thanks.

 

[dave6666]

What is a break-in procedure for rear gears?

A couple of days, and 0 miles.

 

[Madduc]

When I had new gears put in my SRT-10 truck, the gear manufacture said 300 miles of easy city/highway miles and change the fluid after that.

 

[SmokinViperGTS]

Did the fluid smell? If no sulfur smell, it is not really being stressed.

Trying to be a good customer, and stay out of the mechanic's way while he did his thing, I didn't notice when he drained the fluid. However, I can tell you with certainty that the thick coating of it all over the rear body panels stunk like heck! Sulfur? Oh-Yeah.

When I had new gears put in my SRT-10 truck, the gear manufacture said 300 miles of easy city/highway miles and change the fluid after that.

Guess I missed that memo! Makes sense, though.

 

[dave6666]

Guess I missed that memo!

Operator error then...?

 

[SmokinViperGTS]

Operator error then...?

Apparently so, at least in my case.

But in my own defense, I claim complete ignorance, and anyone who knows me will surely attest to the truth in that!

But seriously, after many conversations, and a lot of great feedback here, I've come to some conclusions, and thought that I'd share them here, in case there are others out there who are equally "mechanically challenged" on their Vipers:

1. If you don't track the car, there is no overheating problem. You can just change the fluid on whatever schedule makes you happy, and go on your merry way.
2. If you do track the car, but limit your track sessions to under an hour or so, with cool-off time between, you probably won't have any over-heat problem, but should change your fluid much more frequently - perhaps every 3 or 4 track days. Check for sulfer smell or discoloration using the pinky-in-the-fill-hole technique, and change when noticed. Off you go.
3. If you run track sessions lasting more than an hour, change it every 2 track days or so, or you're likely to have overheat problems. And no, there really aren't any other cheap, reliable solutions out there. Just do it, and off you go.
4. If your stock diff has some mileage or wear on it, the clutches in it start slipping, and add to the heat problem. This can be neatly fixed by switching to a Quaife diff, which doesn't have clutches (gear driven instead), and therefore runs much cooler (and works better, too). $4500, and off you go.
5. And most importantly, any time you change your gears, put a couple of hundred easy miles on them before you track it!!! Otherwise, you will almost certainly have an overheat problem, and get to spend some quality time with your favorite mechanic instead of burning up tires. Who knew?

I'm afraid that's the sum total of my wisdom for today. Thanks to everyone on this thread, and a special thanks to Dan Cragin for his insight.

Steve

 

[JonB]

i owned a 95 that all it ever saw was Heavy Track Duty - along with alot of Hard WTW Racing. I changed fluids regularly. I never had an issue. I believe that if you change your fluids on a regular basis you will not have alot of issues.

Same Here! Tens of THOUSANDS of track miles in Gen 1 and 2, and only severe-service oil chamges with ONE exception 3:73.

SmokinGTS (!!) was AUTOCROSSING!!!! Most Auto-X laps are 50% or less of ONE TRACK LAP TIME!!! Since your gears were recently replaced/set up, i suspect improper lash. Sumthin stinks, and it aint the kitty litter.

If you have a 3:73 diff, they DO run hotter and need a diffy-cooler if tracked. {We have one a LOT less than the P-part kit)

 

[Jack B]

I'm very curious as well, and tend to look for the weak link before applying a large hammer.
Did the fluid smell? If no sulfur smell, it is not really being stressed.
Gear oils are developed using some pretty hefty high temperatures and of course, getting thin when hot should be expected.
What is a break-in procedure for rear gears?
Weak clutches would allow one wheel spin, but if on a track event would this really matter?
Thanks.

Tom:

Unitrax publishes a break in procedure and emphatically claims unless it is followed you will ruin the gear set. Basically you run it for about twenty minutes with absolutely no torque and no de-acceleration. Shut it down and let it cool entirely and repeat the same two more times. I can tell you this i have broken in two new sets of gears with this procedure, the last time I put it on the lift after the first granny cycle and I could not believe how hot the differential was running.

The Gen 1's are not the super Dana gear set and have a smaller pinion gear/shaft. Both the 44 and Super 44 have an issue with the small ring gear bolts and their nasty habit of loosening. As a standard procedure when the gears are replaced you should have the ring gear drilled out for the next size bolt and the bolts wired. I believe the bolts go from 7/16 to 1/2 inch.