I have a TH400 in my car that is on it's 5th year since it was built. It is stock down to the brown clutches, with the exception of a bte transbrake. This year it ran the best time ever of 6.20@114 in the 1/8..but it has not done it again. It has been close, but no cigar. It seem the mph keeps dropping off for no reason. The tune is good and the boost is there. I have changed some thing around and even went to a 9.5" converter. I am suspicious that the trans may be tired. What do you guys think?

 

Your car is making enough power that it probably wouldn't hurt to install some more durable friction materials and upgrade to a 34-element intermediate sprag. What line pressure is the transmission generating right now? There is a pipe plug in the driver side of the transmission case above and to the rear of the shift selector shaft. You can install a 300 PSI gauge in that port to check line pressure.

 

What is the benefit to running reds and kols? Seems like a lot of extra moneys, especially when my trans guy says its not really worth it.

 

Kolene steels are unnecessary. We do not use them in any of the transmissions we build. The Kolene coating is supposed to help dissipate heat from the fluid more quickly. However, the Kolene coating reduces the coefficient of friction between the steels and the clutches. This allows a very minor amount of slippage as the clutches apply. This slippage eventually wears the Kolene coating off of the steels rendering it useless.

Red clutches do offer a strength and durability advantage when used with the appropriate clearances and appropriate fluid. We use red clutches in most everything we build because we have invested the time and money to develop our products around this friction material to make it work, and it has proven to work well for us in a very wide variety of applications. We get excellent wear characteristics with red frictions, and virtually no warranty issues. As a manufacturer that produces thousands of units per year, these are very important factors that must be considered when deciding what friction materials to use in our transmissions. That being said, there are other very good quality friction materials available that work well. Borg Warner OE-replacement brown paper clutches are actually capable of withstanding a surprising amount of abuse. High Energy clutches are also a good choice that work well in a variety of applications. I'm not a big fan of blue clutches or Kevlar clutches as they seem to have a bit more slip as they apply which, in our experience, reduces shift quality and reduces long-term durability of the clutches. When it comes to extreme high horsepower and torque production, red clutches are the ONLY choice for maximum durability and longevity. We have put over 100 consecutive hits on a set of red clutches in a high 3.80/low 3.90 nitrous car and had no visible or measurable wear upon inspection.

 

Tore it down today. We found the intermediate clutches blackened, and the directs were chewed up but not obviously slipping. The sprag in the center support was trashed and the gear and some springs from the governor were in the filter. I am really hoping that this is where my lost et and mph have gone.

 

Your findings are fairly normal for the amount of time on your TH400, especially considering the amount of power going through it. The low roller clutch failure is not completely out of the ordinary. Sounds like a basic freshen-up should get you back on track. How did the intermediate sprag look?

 

I guess it was good, he didn't mention it. Are these problems what was costing me et and mph?

 

Since you found burning of the intermediate clutches you were definitely driving through second gear. This could be the source of the performance loss.

 

I got my trans back yesterday. I put it in the car and it works, so maybe I will get to try it out tomorrow.