2008 Mustang GT - Rebuilt transmission

[Unleashedbeast]

Just had my car returned from the dealer as they rebuilt the transmission (Tremec 3650) due to faulty parts. The car was grinding 2-3 shifts and sometimes 3-4 shifts in cold weather. It also would refuse to shift under heavy acceleration. They replaced

Snap Ring
1-2 Synchro and Blocker Ring
3-4 Synchro and Blocker Ring
and some bearings

I'm sure they topped it off with MotorCraft Mercon V ATF, but here is my question.

I've always ran the factory fluid in the transmission (car now has 30,000 miles - bought it brand new). I'm interested in using Redline D4 ATF as this returned excellent results in my previous car's T56 transmission. It made the shifts much smoother. So, how long should I wait to drain the new fluid and refill with Redline? Is there a break in period I should be concerned about?

 

[AdRock]

Go ahead and change it. It should be fine. I would suggest trying Royal Purple Snchromax. From everything I've seen it seems to work the best in the 3650,

 

[Steve S]

I would guess due to what had to be done is that they didn't put the old oil back in!!! Run it a bit to see if the trans works good then change the oil.

 

[beast3300]

Check it and see if it has fresh fluid in it first. If it is new then I would leave it in.

 

[Unleashedbeast]

No, it can't be the old fluid. The invoice shows 4 quarts of new fluid used, so it's fresh fluid. I just wanted to make sure it wouldn't hurt anything to go ahead and change the fluid.

 

[mechtech2]

Let her break in for 2k or so.
EVen then, it is not fully broken in, just mostly.
Then look at the drained oil in sunlight!

 

[Unleashedbeast]

Originally Posted By: mechtech2
Let her break in for 2k or so.
EVen then, it is not fully broken in, just mostly.
Then look at the drained oil in sunlight!


Yeah, I think I will wait until the next engine OCI before I swap the transmission fluid. I have 4500 miles to go and at least I know the rebuilt would have had some time to wear in a bit.

What would I be looking for in the sunlight scope?

 

[dailydriver]

Originally Posted By: Unleashedbeast
What would I be looking for in the sunlight scope?


All of the silvery metallic 'fines' (which are perfectly normal for break-in, as long as the drained fluid is still more red than silver

).