Mixing Type F and Dex3? (TH350)

[98_SNAKE_EATER]

OK, I have a TH350 w/shift kit in my old Ford Coupe....

Don't know much about it as the previous owner just stated it was new and "Pro-Built"

Checked the fluid and it was a little low on the stick, but I'm not sure what fluid was used

I know most manufacturers that build performance street/strip trannies usually suggest Type F and that's pretty much what I used back in the day on fresh builds, but I'd usually do a dry fill with either Type F or Dex2/3 (never mixed)

Odds are they probably used Type F in this tranny, so I topped it up with a quart of Type F.

A week later, she was down another quart due to a leaky pan gasket, so I drained the pan and replaced the gasket and filter.


Since I wasn't able to drain the converter and was still unsure about mixing, I decided to reuse the same fluid (still looked fresh) and topped it off with another quart of Type F.

Everything seems fine, but I'm still unsure about mixing

Will it cause any problems down the line?




Rick

 

[eljefino]

I bet the trans builder used a decent gasket and, following that, someone serviced the trans with a cheezy (cork?) gasket that caused the leak you found.

If the trans builder really wanted you to run type F he'd have left a note somewhere near the fill or stuck in a dipstick that doesn't ask for dexron. Going with type F for less slip is an old, OLD, hot rod thing.

Whom do you trust more, the builder, the guy who serviced it, or yourself?

I'd stick with the dexron. There are lots of ways to hop up a trans while still using the proper fluid, which I suspect is the route the builder took.

 

[zrxkawboy]

It won't hurt a thing to mix them.

 

[98_SNAKE_EATER]

Originally Posted By: eljefino
I bet the trans builder used a decent gasket and, following that, someone serviced the trans with a cheezy (cork?) gasket that caused the leak you found.


Actually, the gasket used was rubber and still in good shape (I have it hanging on my shop wall as a spare)

The reason for the leak was due to a couple of loose bolts that were used to mount the trans cable bracket.

The PO claimed that the engine and drivetrain only had 200 miles on it, so I'm assuming it was never replaced.

Since I had it down already, I still replaced it with a new rubber gasket and filter.

Quote:
If the trans builder really wanted you to run type F he'd have left a note somewhere near the fill or stuck in a dipstick that doesn't ask for dexron. Going with type F for less slip is an old, OLD, hot rod thing.


It may be old school, but still commonly being used among performance trans builders.

And for all the built trannies I've installed that did recommend Type F, none of them had a note that would actually stay put, just a string tag around one of the mounting holes or some paperwork with bold print.

Quote:
Whom do you trust more, the builder, the guy who serviced it, or yourself?

I'd stick with the dexron. There are lots of ways to hop up a trans while still using the proper fluid, which I suspect is the route the builder took.


The builder, definitely, but there's no way in this case that I can actually get hold of him.

My main concern is the mixing...

At this time, I know for a fact that there's at least (if not all) 2 quarts of Type F.

If I decide to pull the pan again in the future, I'd only be able to replace half the fluid without actually pulling the converter

Lets say worst case I end up with half Type F and half Dex3.

Would there be any negative effects? (foaming, varnishing, heat, etc.)




Rick

 

[onion]

Nothing will come of mixing the fluids, and you likely won't be able to tell much difference even if you change from one to the other.

 

[MolaKule]

Quote:
The builder, definitely, but there's no way in this case that I can actually get hold of him.

My main concern is the mixing...

At this time, I know for a fact that there's at least (if not all) 2 quarts of Type F.

If I decide to pull the pan again in the future, I'd only be able to replace half the fluid without actually pulling the converter

Lets say worst case I end up with half Type F and half Dex3.

Would there be any negative effects? (foaming, varnishing, heat, etc.)



Okay, if the tranny does have a shift kit installed, then the owner defintely wanted sharp, snappy, and fast shifting.

How are you going to be driving it?

If it's going to be your grocery getter, put in Dexron III/Mercon.

If you're going to "track" it or take it down by the river and race it, stick with the Type F.

Don't worry about a quart or two of Dexron mixed with it, just don't race it for now and next time you drop the pan, replace it with Type F.

 

[98_SNAKE_EATER]

Originally Posted By: MolaKule
Quote:
The builder, definitely, but there's no way in this case that I can actually get hold of him.

My main concern is the mixing...

At this time, I know for a fact that there's at least (if not all) 2 quarts of Type F.

If I decide to pull the pan again in the future, I'd only be able to replace half the fluid without actually pulling the converter

Lets say worst case I end up with half Type F and half Dex3.

Would there be any negative effects? (foaming, varnishing, heat, etc.)



Okay, if the tranny does have a shift kit installed, then the owner defintely wanted sharp, snappy, and fast shifting.

How are you going to be driving it?

If it's going to be your grocery getter, put in Dexron III/Mercon.

If you're going to "track" it or take it down by the river and race it, stick with the Type F.

Don't worry about a quart or two of Dexron mixed with it, just don't race it for now and next time you drop the pan, replace it with Type F.


Lately, she's been my parts runner, but I'm not exactly easy on her....

WOT runs and getting sideways in 2nd and 3rd is pretty much the norm for every outing (just can't help myself)