Is that saying that the Penzoil Syncromesh fluid is the SAME as the GM Fluid?

We could use that instead?

 

I am holding a left over bottle of the Redline MTL I put in my tranny last winter. It is an all synthetic oil. This is how it reads:

SAE 70W80
API GL-4 Gear Oil
Satisfies the gear oil viscosity requirements of 70W, 75W and 80, and motor oil viscosities SAE 30, 10W30 and 5W30

*Quicker upshifting and downshifting
*Perfect synchronizer coefficient of friction
*Eliminates notchy shifting even when cold
*High performance gear protection
*Lengthens synchronizer life
*Compatible with petroleum’s and synthetics
*Excellent for high- & low-mile transmissions

I can say the trans shifts better with this oil in it. I have no idea if the Amsoil product is better, it may be? I was placing an order to Summit anyway so I got three quarts of MTL. There is way too much info on the Redline site so if you are into reading that stuff go check it out. It even states BMW transmissions use it somewhere in the tech portion. It goes in to the point that GL5 is not correct to use in some transmissions with soft synchro's.

http://www.redlineoil.com/products_g...sp?subcatID=18

 

Redline makes good fluids and I have used them myself in my Z06 tranny and diff prior to shifting to AMSOIL.

AMSOIL and Redline differ primarily in their basestock. While both a what I would call true synthetics, e.g. they are not highly processed mineral oil like some synthetics, AMSOIL uses a Group IV, or PAO basestock, while Redline uses a Group V or ester basestock.

The Redline has been reported to have caused problems with the blocker rings in early C5 transmissions. This is discussed in the C5 weights, measurements, etc thread under "tough shifting":
http://forums.corvetteforum.com/show...7&forum_id=103

Here is a quote:
"Tough shifting
Manual transmissions -- Replacing the transmission fluid often helps shifting. Early transmissions have paper blocker ring that require Dexron III compatible (usually organic) fluid because some synthetics will destroy the paper blocker rings and subsequently the transmission. Later transmissions, and all rebuilt transmissions, have Kevlar/carbon fiber parts that allow the use of synthetic fluids. I believe the 98-00 transmissions have the paper blocker rings. The safe transmission fluids seem to be: GM Synchromesh PN #12345349, Honda ATF-Z1, Royal Purple Synchromax, Amsoil ATF, O’Reilly Dexron III ATF. The following transmission fluids may be unsafe for early transmissions: Redline D4 ATF, Mobil 1 ATF, Royal Purple Max ATF."

I'm not sure if this issue impacts the C4 or not.

 

I currently have the clutch out in my corvette and was going to fill with the replacement # that gm told me to use, GM Synchromesh PN #12345349, after reading this thread though I'm not sure what I should use.

 

These days there are more
people reporting bad results with zfdoc’s recommendation of bmw 10w-60 motor oil in their zf.

however back then, it was ‘cool’ to run it, what has changed?

why people claiming good results with it in 2005?

but bad results in recent years?

☝️ dizwiz24 was right and got flamed in this thread.

as ive said before, you put castrol bmw 10w-60 motor oil in your bmw engine, not your corvette zf6 transmission.

zfdoc’s advice is outdated/ incorrect / its causing newbs problems who stumble onto his website

gm syncromesh, amsoil syncromesh (or the original zf factory fill pn in your owners manual -if you can find it) should be the only lubricants in the zf6

 

I noticed immediate improvement! As soon as I pulled out of my driveway with the MTL!!!

 

Hi Cajun,
Wow what an endless loop. I searched for Gm 1052931, it was replaced with syncromesh 12345349 which was replaced by 88900333 which is nothing more than 10 4006, a synthetic blend of manual transmission fluid. The ZF factory clearly states that this transmission was designed and built to run on motor oil. I think GM didn't want to make it anymore and just replaced it with whatever they already had for stick shifts.

 

88900333 is absolutely, 100% the correct GM fluid for the ZF6 in our Corvettes. I've posted this in other threads to help clear up confusion. It's not expensive and readily available. As noted above, it's a synthetic blend 75W-80 gear oil which is roughly equivalent to 10W-30 motor oil. I replaced whatever the previous owner had in mine ('89 black tag) over a year ago with this fluid. The difference was immediate and noticeable. The transmission shifts smoothly in all gears and reduced the typical ZF6 noises. You can spend more money for other brands but there is no need.

 

Well, I just put in 2.5 quarts of Redline MTL and couldn't be happier. I have a '96 LT4 bought 2 months ago and I finally got all the fluids changed out now. Like you said, immediately noticed smoother shifting and the zf tranny noise almost completely gone now! I can shift from 3rd to 4th gear with just the flick of one finger. I love this and so fun to drive now!!!