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gamon302 11-09-2019 11:24 AM

Q: Correct weight rear differential fluid? - S302 PJ
I am going to drain and fill the rear differential in my PJ
Am going to use Red line fluid. They list two weights not
sure to use 75w90 or 75w 140. PJ not driven in cold weather
pampered Ohio car your thoughts appreciated

Greg Alspaugh PJ # 412

d3c0d3d 11-09-2019 12:21 PM

I think you would be fine either way, using a synthetic. I would select the weight according to your driving habits since its not driven in cold weather. If it's cruising mostly in good weather than I would go with the 75w90, for example.

Dave 11-09-2019 01:11 PM

The recommendation in owner's manual might be 75W-140 oil for the rear differential.

You will need to add Ford friction modifier (Part #: M-19564-A) for the clutch disk traction-lok rear end.

As mentioned. The weight of your oil will depend on climate and use of vehicle if you stray from OEM.

2007-52 11-10-2019 12:11 AM

Use 75W-140... Redline is great stuff... But check the bottle to see if friction modifier is already included... Redline makes differential fluid both with and without friction modifier added. If your car has a Torsen diff you DO NOT put any friction modifier in.

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gamon302 11-10-2019 11:33 AM

confused on friction modifier and torsen diff ????"
I am not sure what a torsen diff is? I thought PJ's were all the same
as far as differentials were concerned.The red line diff lube 75w90 or
75w140 states it is one of the few diff lubricants that has friction modifiers
already added which poses the ??? do you still add Ford friction modifier
or does that pose a problem.Maybe I am a little anal but these PJ cars
seem to have a lot of different schools of thought among owners concerning what is correct and what is not. I run Castrol full synthetic
5w30 eng oil 6 qts per saleen manual some members say 10w30 10w40
etc.I love the car and want to maintain to my best ability.In no way am I
criticizing the members.This is a great outstanding forum that I enjoy.I
guess when you own a limited production specialized vehicle.In the end
we have to make our own decisions on what works and what doesn't.But
it sure is great to have so many knowledgeable members to help make
those decisions. I can ramble on sometimes Sorry
Greg Alspaugh PJ# 415

2007-52 11-10-2019 12:23 PM

I believe Saleen's "Max Grip" differential was a "Detroit / Eaton TrueTrac"... which is the same as a Torsen. The Max Grip diff was an option for any Saleen car. This style of diff uses helical worm gears instead of clutch packs and spider gears. You can't tell what your car has from the outside. You'd have to have the window sticker, or you could contact Saleen to see how your car was built. I thought many (if not all) of the PJ's had the "Max Grip" diff?

The Torsen-style diffs do NOT use / need any friction modifier. Only differentials with clutch packs (limited slip or "traction-lock" diffs) need friction modifier.

Most differential fluids have friction modifier already added. Redline offers 75W-140 both with, and without, friction modifier. You want to use 75W-140 in your differential... NOT 75W-90. Even your Ford owners manual for the Mustang will recommend 75W-140.

You only need to add friction modifier if you are putting straight lubricant in the differential and the differential is a limited slip style. When you buy Motorcraft 75W-140 it is just straight lubricant, and thus, you need to buy the little bottle of friction modifier too. If you go to your local auto parts store, virtually everything on the shelf will have friction modifier already added.

"Need" to add friction modifier is a little subjective too. It won't hurt anything not to add it. You would only possibly get some chatter in hard turning because the clutch packs wouldn't slip against each other as easily... In other words... It would act more like a posi diff without friction modifier... But most people couldn't tell, or notice, any difference.

Your 3-valve engine was designed to work with 5W oil. It uses variable cam timing which involves solenoids that actuate valving to flow more and less oil into the timing chain gears, which advances and retards the cam shafts. Also, the timing chain tensioners work on oil pressure. Basically the engine is very oil pressure dependent. You should note that even for the GT500 Ford recommends 5W-50 (still a 5W oil)

Saleen and Ford recommended 5W-30 in your engine. For supercharged 302's Saleen recommended 10W-40.

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gamon302 11-10-2019 03:29 PM

2007-52 Thanks for the wealth of knowledge.Greatly appreciated I feel a whole
lot better understanding the difference in the differentials and the lubrication
properties. I don't know if this is true but heard one time that friction modifier
was made from whale sperm. Not sure if fact or fiction.
Thanks again for your help
gamon302 PJ # 412
Greg Alspaugh

Dave 11-10-2019 04:36 PM

The standard differential on the S302 PJ was the OEM Ford Traction-Lok. Saleen did a gear change from 3.55:1 to 3.73:1, but reused the OEM Ford clutch limited slip. "Technically" the 2007 had no available options from Saleen.

PJ #501 had a few differences from the other 499 made.

Aussie-Parnelli 11-25-2019 04:17 PM

1 Attachment(s)
This interesting.
I now run a Detroit True Trac in my race car it gives great traction on hard take offs and the car stays straight, whilst they are a similar design to a Torsen they are much stronger as I found out. Torsen diffs are not recommended for Drag Racing as the gear housing is cast iron photo shows results when they go bang. And with me mainly do hill climbs that is like drag racing up a hill.
I recently asked Steve Saleen what is a "Max Grip" differential is it just a beefed up Ford LSD or a propriety brand......his answer was it is stronger, no real answer to my question.
When I accelerate heavy on my S302E it pulls hard to one side and no way I can keep it straight. I have bought another Detroit True Trac for it, so it will be interesting when I get to take back cover off it to see what was actually fitted.
I believe the PJ's just had the standard Ford LSD with 3.73 gears

Dave 11-25-2019 05:59 PM


Originally Posted by Aussie-Parnelli (Post 149198)
I recently asked Steve Saleen what is a "Max Grip" differential is it just a beefed up Ford LSD or a propriety brand......his answer was it is stronger, no real answer to my question.

I could be mistaken, but something in my mind wants me to say the Saleen "MaxGrip" were different items through time. Yes, I do believe the MaxGrip were over-the-counter differentials. One year the MaxGrip could be one thing supplied by whomever, another year it might be supplied by someone else and something different.

I could be mistaken.

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