: differential failure at 7136 miles; redux



Trionalaw
08-10-12, 01:07 PM
As you know I reported on earlier thread that my differential had supposedly failed when I had the fluid changed the 75w90 after the overheating light came on several times at a driving school two weeks ago. I was informed the fluid was burnt and there were metal shavings on plug. Dealership agreed to replace it.

Forum members said that was all normal and there should be no problems with the differential. Also, it would be safe to drive at yesterday's school at Mid-Ohio. Yesterday the temperature was in 80's not the 90's at Putnam Park 2 weeks ago. Plus I had the heavier, more vicious fluid. I clearly ran faster this time.Certainly cornered faster as I had an instructor who helped me tremendously.

I ran in the competitive mode. The differential overheating light never came on. Serendipitously, I ran into a gentleman who used to run Cadillac racing. I discussed the problem with him. He confirmed what the forum told me. There was nothing wrong with the differential. You need to change the differential fluid if the overheating light comes on. He also agreed that the heavier fluid probably made the difference.

So as usual, you all are right!

By the way, my instructor encouraging me to go faster. He also had me braking later and later. His comment was: "this car has fantastic brakes!" I got the tires to sing. It is still my impression that this beast handles better than my E 90 M3. Probably the magnetic shock absorbers. Maybe not. But whatever, that is my feeling.

Much appreciated and have a good weekend.

Jim

Xaqtly
08-10-12, 01:44 PM
The car DOES have fantastic brakes. The more I drive it, the more I love the brakes. It's not just that they have huge stopping power, it's how they feel. A lot of cars have a more on/off braking thing going on, it's pretty annoying to try to modulate but the V's brakes let you make tiny changes, little changes in pressure that result in an equal amount of braking force. They're some of the most responsive brakes I've ever experienced.

Combined with the MRC in sport mode, it all just comes together at track speeds. As stupid as this may sound, I believe that this car is a better car when you drive it hard than it is when you drive it normally. When you stick it in competitive mode and sport mode and push it with hard braking, trail braking, sharp apexing and full throttle corner exits it feels like an extension of you. This car was just made to be driven hard.

When I drive it normally on my commute, it feels less put together, less communicative, less amazing. And that's not a bad thing, it's just an observation. Even on a commute it's still better than 95% of cars on the road, but that's not where the car shines. If there are any of you who have not explored the limits of this car, in competitive mode and sport mode, pushing its limits through turns and braking, you are missing the best part of this car, the part that puts it into world class territory.

I haven't even gotten mine on a track yet, but I have a lot of track experience and it's pretty easy to see how the character of the car changes when you push it. It wakes up, it responds to your commands like telepathy. It's honestly magnificent, it's almost like a "track sleeper" that doesn't wake up until you're entering turns at 90 MPH.

Anyway that's my Friday ramble. Thanks for the update Jim, I'm going to get my rear diff fluid changed to the good stuff too, see if it gets rid of the whine.

Trionalaw
08-10-12, 02:16 PM
well said. Thankfully, I don't have differential whine.

WA 2 FST
08-10-12, 02:25 PM
Xaqtly... couldn't agree with you more. Very well written post, with astute observations.

SPEED74V
08-13-12, 11:39 AM
Did you use the 110 or 140 differential oil when upgrading?

venomns
08-13-12, 12:03 PM
What Speed said... which fluid did you upgrade too??

caymansbanker
08-13-12, 12:06 PM
Glad to hear all is well. As above, would like to know about the differential fluid.

Trionalaw
08-13-12, 03:26 PM
Amsoil 75w90. That was the weight recommended after I reported the differential overheating at the Putnam Park Raceway driving school.

Jim.

V Wagon
08-13-12, 05:26 PM
Glad to hear you didn't have any issues. Good instructors make all the difference in the world. I will never turn down having an instructor in the car with me. I had friends tell me they would sign me off straight to HPDE 4 when I did my first NASA HPDE as I had quite a bit of other experience. I started in HPDE 1 anyway to make sure I had an instructor as I wanted to learn as much as I could about the track prior to our Lemons race that was at the track a month after the HPDE.

Some people let egos get in the way and want to be in the "highest" run group. You sound like you have a great attitude toward tracking your car and I hope it continues to treat you well and that diff over temp light stays off for you to keep you on track and having fun.

venomns
08-13-12, 05:37 PM
Amsoil 75w90. That was the weight recommended after I reported the differential overheating at the Putnam Park Raceway driving school.

Jim.

Did you have to put the additive in as well or does the amsoil come with it? Thanks!

supratovcoupe
08-13-12, 07:04 PM
Well,

Having HPDE in my MKIV 97 Turbo Supra w/brembos Hoosier's for 7 year's
I cooked my brake fluid on my second run no diff light in my 11 coupe automatic
So next time I am going to put in some motul and hope it does not boil
It's @ Eagles Canyon near Dallas known to be hard on brakes
I thought I could run all day but watch for diff. light. But I had to call it a day I was a little dissapointed with these monster Brembo's we have Oh Well when it's cooler I will give everybody an update....Mark Brown Oh i did pull a 1.01 G going left on the stock tires.

SPEED74V
08-14-12, 09:50 AM
Amsoil 75w90. That was the weight recommended after I reported the differential overheating at the Putnam Park Raceway driving school.

Jim.

I have been running Amsoil 75w90 and it does not get rid of whine...unfortunately. I was going to try the Amsoil 75w110 and see if that makes a difference.

C66 Racing
08-18-12, 09:32 AM
Did you have to put the additive in as well or does the amsoil come with it? Thanks!

AMSOIL Severe Gear Extreme Pressure Synthetic 75w90 (http://www.c66racing-synthetics.com/Product%20Bulletins/SVGPB.htm) (Product Code SVGQT)
AMSOIL Slip-Lock Differential Additive (http://www.c66racing-synthetics.com/Product%20Bulletins/ADAPB.htm) (Product Code ADATB)

The Severe Gear 75w90 comes with friction modifier already in it, and I run that fluid in my 02 Corvette Z06 at the track, and ran it in my 06 CTS-V (daily driver from 06-09) without extra additive and neither diff chattered. But, GM changed the properties of the diff with the introduction of the C6 Vette and the gen two CTS-V and in these newer high performance GM cars, the diff needs more additive, thus most will get the 4 oz Slip Lock Additive and at least put a few ounces in the diff.

Jim - glad to read you had a good day at Mid-Ohio and all was well with the diff.

FYI, AMSOIL has a good DOT 4 brake fluid that I use in my brakes and clutch in my Vette for those that prefer an American fluid over the French Motul:
AMSOIL Series 600 DOT 4 Racing Brake Fluid (http://www.c66racing-synthetics.com/Specialty%20Products/BF4PB.htm) (Product Code BF4SN)
Dry Boiling Point - 580F, Wet Boiling Point - 410F

More than happy to get AMSOIL products for forum members at dealer wholesale pricing, about 25% below retail, via the AMSOIL Preferred Customer Program (http://www.c66racing-synthetics.com/Preferredcustomer.htm). Drop me a PM if interested. :cheers:

Trionalaw
08-18-12, 10:30 AM
My friend who thought the diff had failed decided not too. I will have it added when I changed fluid before next HPDE event in October.

Just read C66's response. I will just get the severe gear fluid.

Thanks

baabootoo
08-18-12, 11:36 AM
I have been running Amsoil 75w90 and it does not get rid of whine...unfortunately. I was going to try the Amsoil 75w110 and see if that makes a difference.

Hmmmmmmm. You might want to rethink that. It's a problem that need to be fixed. That's sort of like running heavier motor oil to get rid of a rod knock at certain times. I'd stick with what the experts recommend.