"magic fluid" to prevent gear grinding (weak syncros) in ZF transaxles
 

Well, 4 quarts of shockproof (red bottle: heavy duty) + an MTL later, my syncro's still grind in 1st/reverse on my track car.

Does anyone know of any thicker fluids that can be used to slow syncro's on older, worn-out ZF transaxles?? Obviously the heaviest Redline fluids don't do enough on really tired transaxles.

Thanks, Mark.

Mark you can fix that easily with a small piece of plastic about 3 3/8" x 2 1/4". Just hand it to your mechanic and a week or so later smooth shifting.

On the early tranny when the syncro wears out the friction surfaces don't make sufficient contact to match the shaft speeds, if I am remembering how it was explained to me, so aint no juice that will put humpty back together again.

The majical fluid, or as I refer to it, mechanic in a bottle, is Kendall Limited Slip additive. It comes in a 4 ounce little bottle and wreaks to high heaven, but it's pure majic, plain and simple. In fact, I'd do a live testimonial for this stuff, it's that good! You can only find it at Napa auto parts stores. You'll know if they sell it or not as soon as you walk in. The smell hits you right away as soon as you walk in the door! Therefore, when using it, avoid getting it on your fingers, clothes, car etc.

It's main purpose is for differentials, but for example, I've used it on cars without reverse. Simply add the Kendall, start the car, and you now have reverse on demand. It's that good, and that quick! Give 'er a try. It'll quiet down your chatter and give you what your looking for too. You'll thank me later!

Todd

I have Redline's LSD additive added, but since the car does not have LSD, it didn't help. I could'nt find an option code and I've seen cars with disabled LSD's where the incorrect fluid was added (I did this on my 951S back in '95 using Mobil 1 gear oil: bad move, but LSD was quickly restored with the correct Redline mix added.

I'm not sure what the Kendall LSD additive would do when the Redline LSD additive didn't help at all. Currently, I have the following mix:
*1 LSD additive (Redline)
*4 quarts Redline heavy duty shockproof
*1 quart Redline MTL

This is pretty much the heaviest mix I can think of.

Mark

LSD additive is to prevent clutch chatter by "reducing" the friction and making the oil slipperier.

Thats the opposite of what you need with weak syncros.

The Kendall trick I think is for auto transmissions, not manual.

I don't see what higher viscousity oil is supposed to help, its a bit more drag on all of the transmission moving parts, so my guess is that it actully makes downshifting harder.

Time for new syncros...been there and there is only one real answer.

Heck, I'll sell the whole car before I spend that $ :) I have another track car being prepped for next year anyway. Just checking to see if there were thicker fluids...

Except for the parts, rebuilding the tranny isn't so bad.

Thicker, thinner, purple, red juice isn't going to fix the syncros once they are worn. When my Mustang was brand new the T5 was kind of notchy feeling, not much just a slight hesitation I didn't like when power shifting. Around a 1000 miles I drained the tranny and put in Redline MTL, and it worked great, but I think that was actually maybe reducing the grab of the new syncros.

You could always look for a cheap used 5 spd in better shape than what you have.

Mark,
Have you tried Redline 75 - 90NS (non slippery)? It's the only thing that has worked for me to help tired synchros. I don't think the Shockproof is what you need. That used for the diff gears under high load.

Ok, thanks guys (Hi Louie), we'll drain/refill with 75/90NS and keep our eyes peeled for another trans: no rush now, my next PCA play weekend is just 2 weeks away :)

Mark

There is not a synchro in the reverse gear. And difficult shifting into 1st (combined with difficulty shifting into reverse) sounds like a throw out bearing issue. Make sure the hydraulics are working properly and the clutch is adjusted correctly.

agreed, .. check the clutch

clutch
 

The clutch, RB, disc/PP, slave, clutch-master cylinder & lines are all new & all heavily purged. "Throw" of slave pin is equiv. to my 18k '86.5 928.

reverse: agreed: but nicks in 2nd and sometimes in first.

Is the intermediate plate position correct? I once fought a DD clutch disengagement problem to eventually find that the intermediate plate had been mis adjusted long enough so that the disks had worn the short splined shaft so that even with correct intermediate plate setting, the disks eventually found their way back to the wrong spot and the clutch would drag. That made shifting appear like bad synchros.

I positioned the IP plate about 3x to get it drag free: it was very tight as I used a new PP with re-lined discs (anticipating a possible turbo kit on this track car): and the discs came out about a mm thicker than stock: this required a perfect bleed and adjustment: I have to be more careful in the future!

Mark