SAM98WS6

Long story short...put redline d4 atf in the M6....broke it...rebuilt it with the best parts Viper stuff...filled with redline d4 atf...hard to shift at high rpms...broke it again...rebuilt it again with Viper stuff...refilled with D4....hard to shift at high rpms...gave up..sold the car.

My buddy buys a viper...22k miles....hard to shift...he has a buddy that work at chrysler that was an engineer on the Viper...calls him to get rebuild info..guy says to try the correct synthetic Castrol Syntorque 75w85 gear lube the dealer sells...(funny thing is the Viper owners manual says to use ATF which is a mistake).

Anyhow he puts this stuff in the tranny...now its shifting like a dream. Its actually unbelievable. Just an FYI. I would never use synthetic ATF ever again.

ls1amit

damn i wonder if that works for the f body t56's ? im currently using royal purple syncromax i like it i mean it works fine.

dailydriver

The explanation I was given as to why they spec that heavy Castrol stuff is that the Viper T-56 gets VERY LITTLE air circulation, and this is the only thing that lets the synchros work while not breaking/shearing from the excessive heat.

SAM98WS6

Ive read where royal purple syncromax is better than the atf but the chrysler engineer says this castrol stuff is the **** and better than royal purple and amsoil. GM repackages the castrol and sells it fyi. i wouldnt have believed it.

I had synthetic ATF in mine...not synthetic gear lube...wish i would have known.

z28drag

iTrader: (19)

i had that problem in my t56 ls1, so i dumped the synthetic and put in gm oil and the shifting went back to normal....

SS4Matt

iTrader: (4)

very interesting, i'm going out and getting a gallon of what you recommend tomarrow and dumping the mobil1 synthetic ATF that's in mine now!

SAM98WS6

I think the GM stuff is called Syncromesh but Im not sure...if its 75w85 it is...i guess its ok at real cold temps...

Peppershaker

Well thought I would give the dodge transmission fluid a try as i was dropping my company truck at the dealers for service and some repairs. So wondered over to the parts department and told them what I wanted the 75w/85w transmisssion fluid for the vipers. The stuff is pricey at $17.95 a quart but went and head and bought it. Drained the transmission on my T56 in my Z28. Let drain for about an hour and then refilled with new stuff from dodge and ther is a big diffance and how shifts now. But the biggest diffrance is when it is sitting there in neutral and the clutch let out it use to rattle alittle and now it has now noise or rattle to it at all now. This is some good stuff.

tici

iTrader: (1)

Nope... it's harder to shift until it's warmed up.
In summer it's better than the ATF, but in winter it's a pain.

MeentSS02

iTrader: (11)

Okay...call me skeptical, but ATF (what the manual recommends) and this 75w85 stuff you are recommending are not even in the same ball park. I'd need a bit more proof before doing something this drastic. Everyone on the internet has a buddy that is really smart, but as an engineer myself, this doesn't even sound remotely close to right.

calhoon

iTrader: (6)

You should follow what the book says. Vipers have always come with carbon-particle blocker ring lining material, F cars have not. The carbon-particle linings tolerate the light gear oil.There are compatability concers with paper lining materials and synthetic -based oils, not to mention cold shift concerns( cold being below 40 degrees F!!!!).

black_z

iTrader: (4)

I agree 100%.

chucky2

Check out the following thread over on BITOG for some info that pgtr put together: More pieces to the Synchomesh puzzle

Dexron III ATF's are like 7.5 cSt at 100C (not sure of their 40C cSt values, you'd have to look those up, but that should be very easy), and according to the info in the link above, Synchromesh type lubes are around 9.1 cSt @ 100C (I know this is accurate because I've looked at the PDS's/MSDS's for most of the Synchromesh's and 9.1 @ 100C is accurate), and the Castrol Syntorq LT is 12.2 cSt at 100C.

I'm not saying the Syntorq LT would be a disaster or anything at 100C (although your definitely well out of manufacturers guidelines here), but the cold shifting may be cause for concern...if you live in a very warm all year climate you'd probably get away with it, but, for anyone living in cooler states, I'd think passing on the Syntorq LT might be a good idea - that, or go super easy until good and warmed up...

That BITOG has some good info in it on this, it's worth a read...

EDIT: Found the MSDS for Castrol Syntorq LT: Present location of Castrol Syntorq LT MSDS

You can tell from looking at SECTION II: PRODUCT/HAZARDOUS INGREDIENT INFORMATION that at least some makeup of Castrol Syntorq LT is true synthetic...how much though they leave you to guess. Also, looks like the BITOG link above was right for the 100C viscosity...without looking back at Redline's site, this stuff is thicker at temp than MTL...just something to think about...

Chuck