Question on fluids for rear end

[97gtscoupe]

So I got the car up on the 4 post to give her a good shake down and check her out while I put on my new exhaust. Figured while it was up there I would go ahead and change out the trans and rear diff fluids in addition to a few other things I am doing. I am a newer owner of this (purchased last fall) and before I put to many more miles on it I really want to make sure she was safe to drive. I already had a rear caliper brake pin issue.

So the main question is, What fluid(s) can/should be used for the rear end? I know there is a Mopar 75w140 as well as an additive that is supposed to be used. Do any other brands work safely? and must I use the additive? I was thinking of using the Royal Purple 75w140 high performance gear oil. Could this be ran safely with out any other additives?

[Boosted Motorsports]

As long as you choose one of the top brand gear oils you will be fine. You still will need to add the mopar friction modifier.

Some have tried to avoid it but you will end up with a loud clunking in corners ad the rear end starts hopping. I wouldn't mess with it just get whatever brand of oil you trust and add the mopar additive and be done with it.

Not sure it will cure your whine noise you had posted about but let us know how the fluid looks when you drop it.

[97gtscoupe]

Thank you! I actually read more about the neutral gear rattle thing and it seems that is exactly what I have. So I am changing out the trans fluid also.

as for the additive. any other brands make a comparable. something like this:
K & W Chemical Trans-X® Posi Trac® Limited Slip Gear Oil Additive, 7 oz.

[Fatboy 18]

As long as you choose one of the top brand gear oils you will be fine. You still will need to add the mopar friction modifier.

I run Amsoil in my rear end, No modifier needed

On the spec sheet it says you can add modifier if LSD "chatter" occurs? What ever that is? ( I don't get any noise that im aware of)

[LifeIsGood]

Is there a reason you don't want to go with the manufacturer suggested fluids?

For my 2001:

MOPAR Synthetic Manual Transmission Lubricant SAE 75W-85 (NV-4500) (MOPAR # 04874459)

MOPAR Synthetic Gear & Axle Lubricant SAE 75 W/140 (MS-8985) (MOPAR # 04874469)
MOPAR Limited Slip Additive (MS-10111) (MOPAR # 04318060AB)

[quickster2]

[QUOTE=Fatboy 18;296739]I run Amsoil in my rear end, No modifier needed

If your service manual calls for friction modifier, than the statement that you run Amsoil (or any other limited slip labeled gear oil), and you "do not need to add the friction modifier", is an incorrect one. Add the friction modifier in the correct quantities as specified. I would not use any other friction modifier than the Mopar specified.

This has been beat to death on this forum already. Each to their own on what works for them.

[dave6666]

Is there a reason you don't want to go with the manufacturer suggested fluids?

Dude! Don't you get it? Anything different than what the manufacturer designed the car with is an UPGRADE! Get on board!

OK, back down to reality, the OEM fluid are great. But feel free to support the aftermarket by upgrading.

[dave6666]

I run Amsoil in my rear end, No modifier needed

If your service manual calls for friction modifier, than the statement that you run Amsoil (or any other limited slip labeled gear oil), and you "do not need to add the friction modifier", is an incorrect one. Add the friction modifier in the correct quantities as specified. I would not use any other friction modifier than the Mopar specified.

This has been beat to death on this forum already. Each to their own on what works for them.

^^^ another owner that knows what the factory knows.

[Lemay88]

Still interesting and confusing to read two very different kind of fluid for the transmission on my '97.
Service book states ATF and tag on the transmission says Castrol Syntorq.
Which one should I go with

[LifeIsGood]

MOPAR Synthetic Manual Transmission Lubricant SAE 75W-85 (NV-4500) (MOPAR # 04874459)

The part numbers are the same...

[Camfab]

Still interesting and confusing to read two very different kind of fluid for the transmission on my '97.
Service book states ATF and tag on the transmission says Castrol Syntorq.
Which one should I go with

Very simple, you run syntorque. At some point the transmission's blocker rings were changed to a different material (upgraded ��) that requires Syntorque. The service manual may not reflect that change.

[Camfab]

I could be wrong about this, but I'm guessing because factory fluids are much more expensive than the stuff you buy at Pep Boys, guys are being frugal.

[97gtscoupe]

Is there a reason you don't want to go with the manufacturer suggested fluids?

Well every car is different, but I have found over the years with many vehicles, especially older ones they find better ways to get the job done, and many high end fluid companies like Royal Purple make a better product or a product that helps with vehicles that may be older, higher miles, tracked, have certain noises or wear issues... or any number of other issues.

With this car being 20 years old, i figured there would be a much better alternative to what the factory put in it in 97.

- - - Updated - - -

I could be wrong about this, but I'm guessing because factory fluids are much more expensive than the stuff you buy at Pep Boys, guys are being frugal.

No the complete opposite actually. I am looking for the best product for the vehicle regardless of price.

[97gtscoupe]

Update:
I went with Royal purple 75W90 for the trans, also picked up RP 75w140 for the rear end but did not put it in because I was unsure about the additive. It is not sounding like there is a good aftermarket or upgraded additive so I will be making a trip to the dealer to pick some up.

[Fatboy 18]

Is there a reason you don't want to go with the manufacturer suggested fluids?

For my 2001:

MOPAR Synthetic Manual Transmission Lubricant SAE 75W-85 (NV-4500) (MOPAR # 04874459)

MOPAR Synthetic Gear & Axle Lubricant SAE 75 W/140 (MS-8985) (MOPAR # 04874469)
MOPAR Limited Slip Additive (MS-10111) (MOPAR # 04318060AB)

The reason I don't go with Mopar fluids is because I can't get them in MY Country unless I import them from the USA which incurs more Viper Tax! Customs duties and Postal handling fee (at a fixed price no mater what the item)

I normally import my Fluids to the United Kingdom through a company in Germany! Nuts!

We do have Jeep Dealers in the UK but FCA use european companies to manufacture their fluids which are different spec to USA fluids.

So Amsoil works for me because its more obtainable and according to their tech sheet exceeds most factory brands recommendations

[My98RT10]

...I normally import my Fluids to the United Kingdom through a company in Germany! Nuts!....

Hey Mark, should not have voted for the Brexit, I guess....

[Fatboy 18]

Hey Mark, should not have voted for the Brexit, I guess....

HaHa! Well we are still in at the moment!