RP fluids for trans and diff...anyone?
Thread Starter
Burning Brakes
Joined: Jul 2018
Posts: 1,113
Likes: 144
From: Miami
RP fluids for trans and diff...anyone?
Guys and gals,
I've read a bit on compatible fluids, but haven't seen much on RP (Royal Purple). I already have some RP fluids sitting around on the shelf and wanted to make sure anyone has ran this, or if I'm missing any friction modifier, additive or anything else. I'm planning to put RP Synchromax on my 1999 T56 M6 and RP MaxGear Synthetic 75W-90 for diff. Diff is stock (1999 FRC with 3.42 final drive). Am I ok with my selection?
I've read a bit on compatible fluids, but haven't seen much on RP (Royal Purple). I already have some RP fluids sitting around on the shelf and wanted to make sure anyone has ran this, or if I'm missing any friction modifier, additive or anything else. I'm planning to put RP Synchromax on my 1999 T56 M6 and RP MaxGear Synthetic 75W-90 for diff. Diff is stock (1999 FRC with 3.42 final drive). Am I ok with my selection?
Last edited by turabo87; Apr 15, 2019 at 01:41 PM.
Thread Starter
Burning Brakes
Joined: Jul 2018
Posts: 1,113
Likes: 144
From: Miami
Anyone? From what I've read it looks like I won't be the first running RP Synchromax and RP MaxGear 75W-90. RP Synchomax is apparently made for manuals that require ATF, and MaxGear 75W-90 has the GL-4 and GL-5 additives. Would like to confirm if anyone with a 1999 has ran SynchroMax successfully long term, despite the supposed claims that the paper blocker rings can't take synthetics.
Melting Slicks
Joined: Jun 2013
Posts: 3,473
Likes: 691
From: West Virginia
Re the M6. Best stuff I have found is Valvoline Dexmerc - spec'd to meet the old DEX III standards, which is what the C5 requires, and labelled "for older GM and Ford vehicles". Plus, it's much cheaper than all the synthetics and there is zero risk in using it on an early tranny -- mine is a '97 built '98 model.. Our local Wallies currently has a gallon jug on sale for $13.97 - it's usually more like $18. BTW, don't believe this fill for life crap (which is what Chevy claimed in the handbook). Changing the fluid at about the 50k mark is worthwhile. I have no leaks, but much to my surprise when I changed the fluid, not as much came out as went in. Evaporation? I don't know. I do know I have a spotless garage floor under the C5. And after the change to Valvoline, shifts are perfect - light and silent. And I run a short shifter.
I did try RP Synchromax in my 5MN K1500 truck in lieu of the OEM GM Synchromesh fluid, purely because it was easier to find. If anything, I had to slow down my shifts a tad to avoid a "chirp" when upshifting. The truck is old, but not many miles (a genuine 72k, I've had it from about 6 months old) and has only had "light duty" all it's life - it was my "get me to work in snow" vehicle until I retired - it now only gets used for trips to Lowes and HD.
I did try RP Synchromax in my 5MN K1500 truck in lieu of the OEM GM Synchromesh fluid, purely because it was easier to find. If anything, I had to slow down my shifts a tad to avoid a "chirp" when upshifting. The truck is old, but not many miles (a genuine 72k, I've had it from about 6 months old) and has only had "light duty" all it's life - it was my "get me to work in snow" vehicle until I retired - it now only gets used for trips to Lowes and HD.
Thread Starter
Burning Brakes
Joined: Jul 2018
Posts: 1,113
Likes: 144
From: Miami
The RP Synchromax is not cheap! But for me it's basically free because I already have some unused stock sitting in my shelves from past years sports cars. So, price aside, that's why I'm asking about the RP Synchromax usage on 1999 M6 T56. I don't have those receipts anymore for the RP, so I'd rather use it if someone out there has ran RP Synchromax successfully.
Racer
Joined: Mar 2019
Posts: 302
Likes: 51
From: Northern NV
Guys and gals,
I've read a bit on compatible fluids, but haven't seen much on RP (Royal Purple). I already have some RP fluids sitting around on the shelf and wanted to make sure anyone has ran this, or if I'm missing any friction modifier, additive or anything else. I'm planning to put RP Synchromax on my 1999 T56 M6 and RP MaxGear Synthetic 75W-90 for diff. Diff is stock (1999 FRC with 3.42 final drive). Am I ok with my selection?
I've read a bit on compatible fluids, but haven't seen much on RP (Royal Purple). I already have some RP fluids sitting around on the shelf and wanted to make sure anyone has ran this, or if I'm missing any friction modifier, additive or anything else. I'm planning to put RP Synchromax on my 1999 T56 M6 and RP MaxGear Synthetic 75W-90 for diff. Diff is stock (1999 FRC with 3.42 final drive). Am I ok with my selection?
About a month ago I put the RP in my Diff with the AC Delco friction mod. No problems so far. The old stuff that came out looked pretty black but my understanding new fluid gets black really fast.
Gonna use AMSOIL in the Auto Trans when I flush it out next week. Already replaced filter but the cork gasket leaks. So I’m going to have it drained again, new OEM gasket installed and the entire system flushed out.
Last edited by lunaticfringe007; Apr 19, 2019 at 12:24 PM.
Melting Slicks
Joined: Jun 2013
Posts: 3,473
Likes: 691
From: West Virginia
There's about one synthetic you can use on a pre 2001 MN6. Plenty of references on here to that effect. Even if the RP is free, it's better to spend the $15 or whatever and get something that is the right spec for the job.
