bogus

I thought that GM sold off their entire stock of ZF6's 7 or 8 years ago?

FASTAZU

I believe they did, but there are many still around, BTW I use Amsoil as that is what Marc H put in it when he installed an NOS ZF6 in mine a few months back.

larryinalabama

http://forums.corvetteforum.com/c4-z...-for-sale.html

dizwiz24

That was in 2002....transmission is fine.

Even if the transmission was messed up, can you explain to me, by that logic, how the supposedly superior 'zfdoc'-endorsed castrol made the problems come to the surface?
As there werent any issues before the change to castrol?

when i replaced the castrol with supposedly 'inferior' gm syncromesh everything worked fine again and i didnt have metal flecks in the tranny fluid anymore....

I have no idea, perhaps the bmw people gave me the wrong stuff. Though it did say castrol 10w-60 tws or something like that.

I am not the only person here who has had this issue. I am certainly the most vocal about it as i dont want others to have this issue.

Use the amsoil for your zf6 trans and use the castrol stuff for your bmw engine.

1991Z07

I've been using the Castrol in mine since the first fluid change in 1993 when I'd had it for two years.

NEVER had a problem with it. EVER.

Smooth shifts, clean fluids on changes.

Maybe you just got a POS ZF...

My black tag seems to do just fine...and there are PLENTY of others who have had issues SOLVED by using the Castrol. You seem to be in the MINORITY.

And I certainly don't baby it...

C66 Racing

And even a few crawling around here.

AMSOIL Synthetic Synchromesh Transmission Fluid (MTF) (Product Code MTFQT)

More than happy to get AMSOIL products for forum members at dealer wholesale pricing, about 25% below retail, via the AMSOIL Preferred Customer Program. Drop me a PM if interested.

dizwiz24

Im not following your intent Or logic.

So my zf6 is a pos because the supposedly smoother shifting castrol doesnt bring those qualities out when its used?

my first step was taking zfdoc's incorrect advice on replacing/bleeding the clutch hydraulics. This did not do a thing.

The only thing that fixed my problem was a switch back to*gm proper fluids for my transmission. Like magic, all those issues went away.

It was almost like the castrol was too slippery or something. It seemed like the synchros needed some friction to operate

I agree with you, it seems like i am in the minority. It does seem like the people raving about the stuff live in some disney world type climate environment vs. the cold he11 temperature changes of ohio. I did a forum search and could find a guy in pa mention shifts were notchier, but he didnt seem to have the wot synchro issues that i did. There was a guy who, like me, had similar problems and switched back. I couldnt find his post unfortunately.

again, i had notchy shifts during regular driving and the synchros didnt work during wot driving. you couldnt even move the gearshift lever into the next gear during a redline wot upshift. It also seemed that the thicker castrol required a warm up period (during regular driving) before the notchiness diminished somewhat.

Now, its obvious my situation is different than yours. So lets discuss some facts.

93 corvette vert
Gm blue tag unit with a 'remanufactured for gm' plaque
New clutch hydraulics and proper bleed procedure
Hurst short throw shifter

I give my advice on here with 10+ years of c4 experience including routine maintenance, modding and racing the car.

I am very vocal about my bad experience with the castrol 10w-60 tws. I dont want to dog zfdoc either as he has helped me out tremendously with other issues such as the trans countershaft rattle and thicker shim.

Who knows? Perhaps it is a pos like you suggest, but im certainly not going to run out and change stuff when it works fine in all kinds of driving environments when the proper fluids are used.

1991Z07

If it is working for you...then go with it.

Your setup isn't much different than mine...just that I have a black tag unit in mine that has 91k miles on it, ALL done by me personally. I replaced the clutch hydraulics last year for the first time. The original parts worked for 22 years flawlessly...but I religiously bleed the clutch system annually. It failed when they had it in the shop changing over the A/C to 134a (after I replaced everything in the system). Even though it was just the slave cylinder, I replaced everything including the hose...it was all original parts and served me well, after all.

You might be touching on the issue with yours...tolerances. It could be the tolerances on your remanufactured ZF are not (quite) right. They could be within the window...but maybe they got them too tight or loose and this is giving you fits with the Castrol.

I've used the Amsoil in it as well...nothing wrong with it. I just get a better deal on the Castrol...so I use it.

I think most owners just don't understand that regular fluid changes are vital to longevity and proper operation. I've changed the ZF fluids about every 20k miles since the car was new. The rear diff fluid has been swapped out 3 times now since I've owned it...so that's 4 fluid changes since the car was assembled. I had the shop replace all the seals on the D44 last fall since the pinion was starting to leak...they said it showed zero wear on the gears, which is something considering I don't just putt around in it and track it quite a bit.

WVZR-1

MAINTENANCE - many C4's see "NONE"

bogus

bogus

I have heard a few folks complain about stiff shifting with the TWS... My only thought is build variances...

Both oils are 10w-something - and if they are the same cold, why would one be different?

Which leads me to build variations...

1991Z07

The friction modifiers are different between manufacturers...and so the clearances would have something to do with how it operates.

Phat98

My question would be if that was really gear oil or some type of shipping oil...BTW, I use Redline (Smurf Blood) in my ZF6.

BigMac2395

I just purchased the Redline.....seems like it will do the job just a bit better perhaps.....not sure....I haven't had this corvette for long...it is my first one and I want to change out the important fluids over the winter.....

GS977

i always ran the tws castrol in the original zf. the new zf has @3000 miles and has only been run with amsoil. it shifts soo much smoother and easier than the original zf with the Castrol.

BigMac2395

Thanks for the advice. I have a new question. It looks pretty easy to drain the fluid from the tranny. But the refill looks more challenging for a novice like myself. Any advice for refilling the transmission? I don't want to attempt it until I know I can refill it confidently. My transmission is in the car. I don't want to remove it.
Thanks. Russell

Phat98

I used about 3' of 1/2" hose, ran it down to the fill plug from the engine compartment right behind the engine. To me it's a little neater than trying to lay under the car using a hand pump to pump it in. Go ahead and dump one bottle in, then start watching while you add the other bottle. Leave your drain pan under the trans to catch any overflow.

I'm sure some of the other guys here have their solutions that work for them. More than one way to skin a cat, ya' know...

ninetyfivevette

In mine, I preferred the shifting action of RedLine LWS over the Castrol 10W-60 and Amsoil. The LWS is definitely a bit thicker, probably a bit higher shift effort, but never locked me out of third. Probably was helping my aging syncros. Or maybe it's because LWS is made from Smurf blood.

Hib Halverson put up a pretty convincing write-up on LWS a long time ago over on CAC.

BigMac2395

Where can I fnd that article? Bill from CaveCreek, AZ also recommended the hose as well. He also said the redline is ok to use. He uses the castrol in his rebuilds though. Thanks in advance to the link to the article.
Russell.

Phat98

I concur! Maybe it's the individual transmission's synchro conditions, but Red Line has worked the best for me. I would rate the Amsoil second, some of the shifts still felt a little notchy while using it. The trans has 169K miles on it so maybe that's why the Red Line works better.