Mach 1 Club

Full Version: TR3650 - Tremec 3650 1 -2 and 2-3 Shift Clunk and Grind Fix
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This is intended to give members a direction if they are experiencing any issues this is not intended to be the last word on this subject, do your homework before attempting anything mentioned here.


There are different problems with this trans. Most common seem to be 1-2 and 2-3 shift clunk. The other is grinding into gear.

Well here is my fix for a 1-2 clunk. When my Mach 1 was cold this was VERY noticeable. Had to shift very slowly and ease it in gear. Would take 10-15 minutes of driving before it started to go away, even then I would hear it every once in a while.

Called Tremec. They told me two things about the Tremec TR3650:

- Dump the factory fill (was told by Tremec For used Mobil 1 syn). Replace it with Texaco (Havoline) Dexron III.

I replaced it with Royal Purple Synchromax. It is synthetic and I did a lot of research and a thinner cold temperature fluid seemed to be the best choice.

- Drop the fill amount from Ford's recommendation of 3.8 for the Tremec TR3650 to 3.2 quarts.

They said this would fix the 1-2 shift clunk problem of the Tremec TR3650. I wasn't as sure as they were. What do you know, it worked. No clunk with the Tremec TR3650 and the new fluid change and level, even when I try to get it (pop the clutch a little too early). Don't even get it on a fast downshift like I used to. Feels great. If anyone has a shifting clunk I would highly recommend the change.

Shouldn't take you more that 20 minutes to do:

- Warm up the and get it up on ramps or jacks. The higher the better as the fill hole is a little tough to reach.

- Use 3/8 inch ratchet to remove drain plug (bottom rear of trans).
- Clean / replace plug and remove the fill plug. Same type plug, higher up on passenger side of trans rear.
- Don't use a 2 hose hand siphon pump on the Tremec TR3650. They are garbage for this job, trust me. Go to Meijer and buy a pump that screws directly to the top of the trans bottle. Make sure the "fluid out" least 1 foot long to reach the fill plug. The "fluid in" line to the pump drops right down in the bottle. Makes it easy to pump out 99% from the bottle.
- fill with the Tremec TR3650 with 3.2 quarts (3027 ML to be exact). Bottles are marked in ML's.
- Replace fill plug and your done.

I am extremely happy with how the Tremec TR3650 is shifting now. I ran it through is paces hard, even cold and it is great.


Seems as if you have been doing alot of research on your own .

I wonder if advanced adapters makes a kit yet to adapt the new
6 speed manual transmission to the older 351 cleveland or windsor or even the 428 Cj engines yet?SCo_hmmthink
If I could get paid for reading and studying Mustangs Id be a rich man! Biggrin
It's been two years since you posted this tech tip. Are you still happy going with the Royal Purple Synthetics? My tranny is doing the same thing now. I thought it was because she had over 110k on her.