haxxx

I changed my transmission fluid over a year ago with the Castrol engine oil and it was absolute garbage. A lot of people seem to have problems with it and it had absolutely terrible synchro engagement. No grinding from what I could tell, it was just terrible to drive with.

I dumped that pretty quickly for Penzoil synchromesh which was significantly better, but not nearly as good as the factory stuff that you can no longer buy. For whatever reason it mostly felt great, except third gear engagement was harder, and first didn't want to engage maybe 50% of the time if rolling slowly.

OK maybe this is a bit long winded, but I finally decided to try the Amsoil and it is easily the best. I haven't been able to drive it a lot but I tested the slow rolling first gear engagements I was previously having trouble with and they are perfect now. Third gear is also a significant improvement so I am very happy.

This time I used the Harbor Freight transfer pump instead of the screw on type. Even if you only use it once and throw it away after, it is worth it. I put my car up on ramps so with this transfer pump I can pump the oil into the transmission and switch bottles without being under the car, so much easier. If you use it take into account the pump holds about 4 ounces of oil.

https://www.harborfreight.com/multi-...ump-63144.html

mickey5

GM has a manual trans synchromesh oil that I used at the 50K initial oil change. What I put in worked as well as what I took out. Very smooth gear changes and no lock out even in cold winter.

cv67

Remember the daily castrol threads, never drank the cool aid
Plus Im cheap, pennzoil syncromesh was great.

May try the Amsoil on the T56, perhaps its the crappy B and M shifter but the occasional notchy feel dries me crazy perhaps there is something to Amsoil.They have been around forever.

9T3VETTE

Good to hear, this will be my first project in the spring. I’ve had problems with 3rd to 4th wide open throttle engagement for awhile. Hopefully some new better fluid will clear it up.

B17Crew

I’ve been using Amsoil Synchromesh fluid in my ’96 for some time now. I attribute the smooth shifts like a hot knife through butter due this fluid:

https://www.amsoil.com/shop/by-produ...n-fluid-5w-30/

B17Crew

QCVette

In my '95 ZF6 I was having a little bit of an issue from 1st to 2nd when it was cold. It wouldn't grind, but it was stiff or notchy when going into 2nd. It just didn't feel right.

I switched to Amsoil a couple years ago and it has shifted normally since.

jpipx

I've got this fluid change on my radar, going to use the Amsoil Synchromesh as well.

When you guys changed your ZF6 fluid, did you warm up the transmission before the change? The FSM said to warm it up so that any moisture which may be present is removed. I have my car up in the air right now while I do my winter maintenance, wasn't sure if I should wait until warmer weather and take it for a ride first or just do it now. Thanks!

Tom400CFI

Just do it now.


I changed my '92 from what ever was in it to Amsoil...I think it shifts worse now. The 'Vette Kart ['89]) has some clearish oill in it (came in it) and it shifts awesome. IDK....

B17Crew

Yes, mine was warm. Changed it after an hour of mixed driving. Make sure you are able to remove the fill plug before removing the drain plug.

B17Crew

mazdaverx7

I used BG Synchroshift in my MR2 Spyder as an experiment. The shifting was really transformed into an enjoyable experience and was no longer as notchy. With that said, I think I'm going to spend the extra cash and switch all of my cars over to the stuff. I have used the Penzoil Synchromesh in the past and haven't had any complaints. This stuff though I feel is far better and would be on par with the Amsoil.

Eljay

I have about 3000 miles on Red Line MTL in my 91 no complaints so far.

rocco16

I put the Castrol TWS 10w-60 in the ZF6 about 40K miles ago. Never have been happy with the shifting. Guess I'll try something like the Amsoil. The MTFQT-EA does meet GM spec for trans fluid.

cv67

Mines the same way perhaps Ill give it a try. If that doesnt work Im switching shifters.

car addict

Am using the same - BG. No complaints.

rocco16

The BG Syncroshift is a 75W-80 gear lube. The Castrol TWS oil that ZF Doc recommends is 5W-60. The Amsoil Manual Syncromesh Transmission Fluid is 5W-30.
Big difference in viscosity between 75w and 5w. I wonder if this is a concern?

haxxx

I believe the 12345349 gm fluid the Amsoil replaces was 5w-30, but I could be wrong. The previous owner of my car had the transmission fluid changed maybe 10 years ago with that fluid and the car shifted beautifully.

As for oil weight, manual transmissions aren't nearly as complicated as engines. Engines have all the various pieces with specifically manufactured tolerances where oil needs to fit, flow, and stay on these different parts from cold to hot to keep the engine lubricated. Manual transmission fluid really just need to protect the syncrhos and (hopefully) help them engage, so I don't think oil weight is nearly as critical. I'm sure it's more complicated than that but that's my basic understanding.

car addict

After reading this post I had to check my work order to see what actually I have in my trans. I had my trans, diff, and cooling system flush all done at a shop.The parts list says BG Synchro II but the labor says drain and fill with 5w30 gear lube. I'm going to believe I have BG Synchro II. It costs more . At any rate I have no issues with my shifting.

QCVette

It can be misleading if they are measuring using different scales. A 10W30 motor oil is about the same as a 75W85 gear oil.

See the link below for a comparison.
https://www.bobistheoilguy.com/viscosity-charts/

rocco16

Thank you, QCVette. I learn something new every day.

TorchTarga94

I've been running the Amsoil stuff since 2011 or so. Very happy with it.