Well, I've been trying to figure out why my car launched GREAT but had no MPH on the big end. The tranny was also slipping quite a bit, because going through the traps at 128mph my rpms were close to 7k. (and thats with 3.73 gears and 28" tall tires)

At any rate, I called yank and come to find out I put the wrong fluid in my tranny. I had drexon 3 and should have been using Ford Type F fluid.

Mike at Yank didn't think that putting the wrong fluid in there had an effect on the internals, but said having it in there would have caused the tranny to slip a lot. He said if I put the ford type F in there it would fix everything right up and the tranny shouldn't slip anymore.

My question is, does this sound right, or should I go ahead and have the tranny rebuilt? I'm going to the national F-Body event and want to make sure my car is in tip top shape. BTW - Tranny only has like 500 miles on it.

Thanks,
Jason Fetter

 

"Mike at Yank didn't think that putting the wrong fluid in there had an effect on the internals, but said having it in there would have caused the tranny to slip a lot. He said if I put the ford type F in there it would fix everything right up and the tranny shouldn't slip anymore."


I don't believe this sounds right. I have built and run quite a few Turbo 400's and have never used "Type F" fluid in any of them. In many of the shift kits they say you can use Type F fluid to make the trans shift harder. This happens because the Type F fluid swells the seals slightly and makes for a more positive seal in the clutch packs.

By the way, my Turbo 400 has been behind a 433 in. BBC that dyno'ed at 632 hp (before applying the NOS big Shot system) for 5 years with no slippage and no failure.

My .02

 

Many after market rebuilders use type-F fluid. I would certainly give the manufacturer suggestion a try before listening to some one on this board.

Also I believe that type-F has a higher coificient of friction, than Dextron, and thats why it shifts better not that it swells the seals.

 

I agree with Z28SORR's statement, " I would certainly give the manufacturer suggestion a try before listening to some one on this board ". Since the manufacturer of the transmission is GM and they use Dexron fluid....I guess you should use dexron!!

 

Cute, but your not getting off that easy.
We could have a long discussion about fluid dynamics, Hydrolics, and oil chemistry, but the bottom line is; that the fact that you've had some good luck with you TH400 has nothing to do with this individual problem.
Yank rebuilt the trans. to their specs. not GM's. I assume they want to keep their customers happy. If they recommend type-f fluid I would listen to them not you or me.

 

Yank might have built the transmission to "their specs", but type "F" is only required when running "asbestos" type clutches. Type"F" DOES NOT have a "higher" coefficient of friction on "dynamic" clutches, (2nd gear, 3rd gear) as does Dexron III. TYpe "F" has a "higher" coefficient on static clutches (neutral to drive), according to Borg Warner, Raybestos, and Alto. There is nothing that Yank could do to change this requirement. When have any of you seen a change in MPH or ET (minor amounts maybe) by changing fluid in a good transmission? Type "F" will make the clutches come on all at once at the end of the shift, thereby giving the "feel" that the shifts are firmer. With the Dexron III, the clutches start to come on at the beginning of the shift. I have built several hundred TH400's over the years, all with a good quality Dexron II. As you can see, "Old ways die hard".