Which Oil (tranny & diff)

[dturb]

So I'll be changing the tranny & diff fluids (98 2.8 roady) in the next few months. I've done some research here and think I've figured out what to use in the tranny, but can't come to a 100% decision on the diff.

Tranny - Royal Purple Synchro-Max 01512

Diff - Royal Purple 75/90 01300
AMSOil 75/90 SVGQT
AMSOil 75/110 SVTQT

Can any of you point me in the right direction? Or have a better option for the tranny?

[z3540i]

This subject seems to be covered Every week...It boils down to personal perferance! Everyone has a different opinion of what is "The Best"

Transmission i run Dextron 3 Synthetic ATF (Getrag 5 speed)
Diff..I use Lucas Heavy duty 85w-140 (3.73 diff swapped from an e30)

[rf900rkw]

Yes, after years of hashing it out, the consensus of the forum is they all suck.

[PwrdbyM]

Red Line 75w90

[mva]

So I'll be changing the tranny & diff fluids (98 2.8 roady) in the next few months. I've done some research here and think I've figured out what to use in the tranny, but can't come to a 100% decision on the diff.

Tranny - Royal Purple Synchro-Max 01512

Diff - Royal Purple 75/90 01300
AMSOil 75/90 SVGQT
AMSOil 75/110 SVTQT

Can any of you point me in the right direction? Or have a better option for the tranny?

Good choice of tranny fluid.

Either tranny choice is good. Go with the 75/110 if you want to quiet it down a bit.

[Msilvia]

I use royal purple in all three of my S52 powered cars. Synchromax in the tranny and the 85w140 in the diffs.

Smoothed out my notchy shifting due to the previous redline that was in the Mcoupe.

[PbFut]

Any good quality 75/or 85 - 140 will be fine for most applications in the rearend. Believe it or not, the oil that comes out the clearest in FrankenCoupe is Valvoline 75-140 Synthetic. You can pick it up for $11.50 a quart at Napa. As far as the tranny, it is a little more sensitive to the type of driving you do, needing balance heat ability with cold shifting of which I can’t add much info on.

[calimanusa]

I use royal purple in all three of my S52 powered cars. Synchromax in the tranny and the 85w140 in the diffs.

Smoothed out my notchy shifting due to the previous redline that was in the Mcoupe.

Any particular reason why you went with 85w-140 vs 75w-140? Royal purple makes them both and I'm trying to decide. Thanks!

[coolguy147]

Any particular reason why you went with 85w-140 vs 75w-140? Royal purple makes them both and I'm trying to decide. Thanks!

Go 75w-140

[Bimjam96]

I use royal purple in all three of my S52 powered cars. Synchromax in the tranny and the 85w140 in the diffs.

Smoothed out my notchy shifting due to the previous redline that was in the Mcoupe.

I know old thread from the dead but I actually switched from royal purple synchromax to redline mtl and that reduced my notchy shifting. I think there's no good answer

[spidertri]

How old was the royal purple? I just switched from 1 month old amsoil to fresh royal purple and the difference was night and day.

The amsoil made shifting much notchier and generally felt terrible, the royal purple took away all notchiness and made driving enjoyable. When it was cold the amsoil actually caused 5th gear to stick, that was why i decided to change it so soon again. No sticking 5th with royal purple.

I've found in the past that royal purple wears out within 20k miles. There are other threads showing that RP matches the OE fluid pretty closely in terms of viscosity.

[Jay11]

2k Z3 2.5 Roady
What is the capacity needed for each-tranny and diff?