TheGreek!

In a thread I made about the noisy six speed trans in my car someone said to use GM synchromesh or amsoil synchromesh fluid in it because other oils will cause the trans to be noisy. The local parts stores don't have either one and when I called the local Chevy dealer they want 20 bucks and some change for a quart of the GM oil! I need around 2-1/2 quarts according to the service manual which means I'll have to cough up over 60 bucks (plus 9% sales tax here in AZ) for 3 quarts of oil! Is there a cheaper alternative or do I have no choice but to bend over and get *** raped for the oil I need? Any help is appreciated.

Edit to add: The part number for the GM oil in the service manual (#1052931) has been changed/superceded to part number 88900333.

billschroeder5842

Amsoil is the one to you want. Yes, it is expensive but measurably cheaper than a transmission rebuild.

Unfortunately these 30 year old cars break and can get expensive.

TheGreek!

I found some threads on here about the oil and the opinions vary widely. Some say to use 5w30 synthetic motor oil, others say to use 10w60 BMW synthetic motor oil (and then I read some posts saying not to use it), others say to use the factory GM oil (which some say is 5w30 synthetic motor oil), others say to use Amsoil synchromesh oil, and others say use Pennzoil synchromesh oil. What should I use? Are all of them good?

TheGreek!

It's not that I can't afford it, but damn, almost 70 bucks for three quarts of oil (after sales tax) is a bit stiff. If there's oil out there that will work just as well as the factory GM oil for less cost I'd rather go that route and put the savings towards other things.

GREGGPENN

I've seen several replies where owners have used Pennzoil Synchromesh. I'm guessing it's cheaper? I've tried the Castrol AND refilled with Amsoil twice PLUS GM's too. That means I've forked over $60ish about 4 times to keep mine "serviced". People that pay a shop for their work -- pay more. BFD.

As for the "buzzing", I hope you're not referring to slop that can form in the shifter assembly -- causing "buzzing" in the linkage? I'm thinking my reverse lift-ring buzzed quite a bit before I converted to eliminate it. If the trans is really buzzing, I don't think lube is the issue. In over 15 yrs on this forum, I don't recall "buzzing" being a side-effect of lube choice.

Nokones

GM Manual Tranny Oil only. Pay for the oil now or pay for a tranny later. If you decide to pay for the tranny later you won't have far to go to get a rebuild tranny. The ZF tranny service parts are not and were not available. I only know of one source that rebuilds the ZF Trannies and he is in Cave Creek. www.zfdoc.com

billschroeder5842

BTW... My ZF6 in my ZR1 is the NOISIEST transmission I have ever had. It clunk, wheezes, jerks and that dual mass fly wheel is just a sound factory. I have a 04 Z06 with a TREMEC M6 and that thing does not register on the sound scale.

I've come to terms with the ZF6 and just console myself that all the noise means it is working properly.

TheGreek!

Does anybody know what the viscosity is of the GM oil? Is it thin like automatic transmission fluid or is it thick like gear lube? Or is it more like 30 weight motor oil?

GREGGPENN

5w-30....just like equivalent motor oil. (Not the same though...manual trans fluid has friction modifiers to achieve proper synchro engagement.)

billschroeder5842

Greg, I would not over think this too much. If you get any name brand "synchromesh" level fluid, I can guarantee it will be WAY better than the old fluid you have in your current transmission.

Unless you are tracking your car, you will be fine for everyday spirited driving.

Purple92

So - if you do a search on lube recommendations for the ZF-6 Speed gearbox, you'll find all kind of advice. Some of the advice you'll get is good and some is just plain stupid !!!

I get what you're saying about $20/quart fluid. You just know that the stealership is buying the stuff for less than $10 and making a ton of profit on it...... My fluid of choice for the ZF is the Redline MT-90. It is thicker than the 5-30 motor oil others have suggested. I'd suggest calling Redline's tech line and asking their recommendations. (BTW - The Redline oil is available through places like Summit and Jegs, and typically runs about $12/quart.) I would recommend changing the gear oil, as every single time you shift - there is some wear, and the worn metal from the synchro rings goes into the oil. Draining the old oil out and refilling with new is the only way to get rid of that worn material.

Two suggestions - make sure you get either a 17mm allen key or a 1/2" Drive 17mm allen "socket" as the fill and drian plugs can be a bit stubborn, and always remove the fill lug before you remove the drain plug. You'll also want a small "hand pump" that you can use to pump the new fluid from the container into the tranny - as there isn't much room to get the bottle of lube into the fill hole....Truthfully - I doubt the fluid change will make the noises go away - the thicker oil make quiet things down a little bit - but at least you'll know you have fresh fluid in there... And after you're done with the tranny - you can do the diff fluid ... and then the brake fluid ... and the coolant .... and the power steering fluid ...

billschroeder5842

You can get a spare drain plug (you may need one) from a VW dealer.

DGXR

I used the Pennzoil Synchromesh for the first tranny oil change, no problems. But it's not synthetic so I only used it for about 8,000 miles. I have used Amsoil Synchromesh ever since, it is fully synthetic so I run it for about 12-15,000 miles. I disagree that "any synchromesh" will work fine in these transmissions. The factory fill was a Havoline 5w30 motor oil with friction modifiers (and other stuff) added to make it compatible with the synchronizers - the GM oil is a good equivalent, as is the Pennzoil Synchromesh. The Redline light shockproof is also supposed to be good but I have no personal experience with it.
DO NOT use standard 75w90 gear oil. Also I suggest not using the 10w60 BMW motor oil -- motor oil belongs in motors.

turbobuick33

I plan on using Valvoline synchromesh

dizwiz24

JasBass

Im running the recommended redline in mine and it's been just fine. I have a DMF to SMF conversion flywheel and she definitely rattles. But no amount of oil is going to make up for needing to shim up the countershaft. Bottom line, you aren't going to hurt your trans using any of the oils in this thread. Just decide what you're comfortable with and roll with it

NASCAR314

The GM fluid is available at GMpartsgiant for $11.56 / quart plus shipping of course. In case anyone is looking for the lowest price on the genuine GM synchromesh fluid.
GM part no. 1052931

GREGGPENN

GREGGPENN

There's apparently truth to this considering feedback from users of the "recommended" MTF or even lightweight shockproof fluids by Redline. From what I've read over the years, it's about split equally between MTF and the lightweight fluids they sell. Redline would recommend the MTF -- if you called them. Ironically, the lightweight is closer to original stock GM (ZF) fluid viscosity.

TorchTarga94

I've never been a huge fan of Amsoil due to their pyramid type business structure and limited places to buy it from due to it being sort of a boutique oil, but when it comes to the ZF6, its really hard to beat the way Amsoil makes the transmission feel. I change it once a year regardless of mileage as cheap insurance. Overkill? Absolutely, but its once a year and I do all of my other maintenance at the same time. Really makes the car a pleasure to drive. I've been using it since 2011. I actually tried the pennzoil stuff a few years ago since it was available locally at Advanced. I immediately noticed a negative change in the shift effort. I ordered some Amsoil right away and back to smooth shifting.