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rear diff oil question

Mad Hatter

Gotta go Faster
3,893
2,389
Santiago, Chile
Hi, last track day I had a longer then usual session of about 30 min hard driving. I noticed the rear axle breather put oil all over the brake and wheel. I have redline 75W90 gear oil. Would it be better to go to 85W140 Royal Purple or 75W140 Redline??

And yes! get a catch can!
 
584
164
Moving the OE breather isn't a long term solution in my opinion - I got tons of overflow even from the turkey baster upgrade mounted on the top of the diff.

High speeds get the fluid spitting out pretty regularly. I had a Bob's catch can, but with P springs I couldn't get enough clearance between the canister and the top of the diff so I plugged the diff and ran the hose off the driver's side axle. That worked fine on P springs, but when I installed my coilovers (and lowered the ride height a little), the hose fitting on the axle made contact with my over-axle exhaust and cracked the fitting.

I now have a JLT axle breather that I am going to try to run off the top of the diff (it uses a smaller canister that only mounts on one side of the UCA and you have some leeway in how you mount it).

Sorry for the long post. Just thought I would share my experiences.

John
 

Grant 302

basic and well known psychic
Mad Hatter said:
Thanks Grant, will try the RP in the heavier grade. And move the dam breather as well!

Sent from my GT-I9100 using Tapatalk 2

No problem.

IIRC, the plug size needed is 7/16-20 straight thread. I used a small (maybe 1/4"?) male-male flare fitting with a cap.
 
I have the Bobs catch can with P springs and that setup works fine for me.

Grant why would run a heavier oil than spec?
 
1,022
97
Exp. Type
HPDE
Exp. Level
10-20 Years
Texas
How is the JLT working out? I have Sportlines and Bob's catch was making contact to the point that it broke the fitting so I had to take it off. I am looking for something smaller and will go with the JLT if it works. Thanks
 
584
164
Hey FlyboyGSXR - I haven't installed the JLT yet, hopefully in the next week or so. I went to the hardware store and bought several new fittings to try out just in case. If you look at the JLT, it only uses one UCA bolt and you can rotate it to get around the diff so there should be plenty of room.
 

Grant 302

basic and well known psychic
NFSBOSS said:
I have the Bobs catch can with P springs and that setup works fine for me.

Grant why would run a heavier oil than spec?

Do you want the long or short answer? ;)

I don't have a diff cooler and I am using a heavier weight to (hopefully) be in the right viscosity range on track and in the SoCal heat. Or looking at it the other way, I don't run straight 190 or 250, because it is also a street car and this is the best compromise available to me. I also think it should run quieter considering 3.73s in both cars.

I've taken temps of the diff case coming off track at LS in low 70* weather and have recorded temps of over 260*F.
 
584
164
Installed my JLT axle reservoir today. Very easy to do and plenty of clearance it seems like. I installed the canister using the passenger side UCA bolt and ran the hose down to the top of the diff.
 
1,022
97
Exp. Type
HPDE
Exp. Level
10-20 Years
Texas
Cool…I will be installing mine later this week before I head off to the SVT Superfest. I also bought the new diff cover with the drain plug and a diff locker gasket…I think that's what it was called. I'm tired of pulling the cover every time I change the fluid.
 
Catch can breather in trunk. Line routed from top of axle tube through hole in trunk. No more gear oil problems :)

Sent from my DROID4 using Tapatalk
 

steveespo

Lord knows I'm a Voodoo Child
Moderator
3,752
1,223
Exp. Type
Time Attack
Exp. Level
10-20 Years
NY Metro
Guys and gals
I know I may sound like a broken record but the thatch cans while necessary and great are only masking the real issue which is excessive lube temperatures on track. If you don't track your car you can tune out now. For those who do if you don't run a cooler setup then please change your diff fluid every 4 hours per the Boss supplement. I ran last Saturday in 60 degree temperatures and again saw diff oil temps hit 260 degrees at which time I turned on my cooler pump and brought them down to 235 deg. My tell tale light came on at lap 9 of a 18 lap session so temps I'm sure would have climbed even higher. One other fix I am going to try is wrapping my over axle pipes from the x pipe connection to the peak of the over axle with DEI Titanium grade exhaust wrap. It's a tip I saw on SVTPerformance.com for the guys having issues with the IRS pumpkins in their Terminator Cobras. This will also help protect my new DSS Carbon fiber driveshaft that I'm installing Tuesday.
Steve
 

steveespo

Lord knows I'm a Voodoo Child
Moderator
3,752
1,223
Exp. Type
Time Attack
Exp. Level
10-20 Years
NY Metro
Ford specified 85W140 Full Synthetic. I also put the friction modifier in there although its not really needed for Torsens.
This is also a good alternative
http://www.mobiloil.com/USA-English/MotorOil/Other_Products/Mobil_1_Fully_Synthetic_Gear_Lube_75W-140LS.aspx
As is this
http://www.redlineoil.com/product.aspx?pid=134&pcid=4

I don't recommend Royal Purple products based on a previous bad experience with a traction lok rear exploding. Not in this car.
Steve
 
158
29
I opened my differential to do the rear brake upgrade and I did se some signs of having excess heat in the rear.The more I looked at how close the pipes run to the center case the more I know it has to add heat to the area.I got some wrap and two different sleeve setups from DEI to keep the heat away.I'll snap a few pics tomorrow when I'm installing and we will see if it makes a difference at VIR next weekend.I'll bring my IR heat gun and do some comparison.
Guy
 
gww52 said:
I opened my differential to do the rear brake upgrade and I did se some signs of having excess heat in the rear.The more I looked at how close the pipes run to the center case the more I know it has to add heat to the area.I got some wrap and two different sleeve setups from DEI to keep the heat away.I'll snap a few pics tomorrow when I'm installing and we will see if it makes a difference at VIR next weekend.I'll bring my IR heat gun and do some comparison.
Guy
In for the update.
 
1,281
3
Tulsa, OK
steveespo said:
Ford specified 85W140 Full Synthetic. I also put the friction modifier in there although its not really needed for Torsens.
This is also a good alternative
http://www.mobiloil.com/USA-English/MotorOil/Other_Products/Mobil_1_Fully_Synthetic_Gear_Lube_75W-140LS.aspx
As is this
http://www.redlineoil.com/product.aspx?pid=134&pcid=4

I don't recommend Royal Purple products based on a previous bad experience with a traction lok rear exploding. Not in this car.
Steve

I may be wrong but I thought Ford recommended 75w140 in these cars?
 

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