Bizarre TH400 issue

[n4ue]

Hi to all. I love this site and learned a lot.
This might be wordy, so PLEASE bear with me....

I have a very strange issue and wanted to touch base with any TH400 experts out there.....
I've been a drag racer for decades and at the present, I have a TH400 in my pro street car. I actually have 2 complete spare TH400s. As a drag racer, I never broke the internals, just the case, when I broke a drive shaft. Just mentioning this, because I've 'freshened' up a few.

The car has a TH400 that has worked perfectly for MANY years, but only gets about 200 miles/year. Last week, I made the mistake of using some 20 year old "Nitro octane booster". It made the car almost undriveable. As I was limping home, I saw a huge cloud of smoke from the passenger side of the engine. I cut the fuel pump immediately. At the same instant, it felt like the rear end locked up.
A braided fuel line had ruptured inside (9 psi) and this 'fuel' landed on the header.
After refurbing the fuel system, I have this weird problem:
(The TH has a manual valve body (reverse) and a trans brake, with a 5500 rpm converter.)
The 1-2 shift is great as usual, but when I do the 2-3 shift, it feels like the transmission is almost locking up! With the converter I use, I can normally downshift from 3-2-1-N at pretty much any speed.

I just cannot connect the fuel issue with the transmission issue.
The TH goes into Park, Reverse, Neutral, First, and Second gear perfectly. Fluid is clean, and full. I've always used a large cooler with all my TH400s.

Any thoughts???

Thank You!!!!

ron

 

[xxch4osxx]

Sounds like a good question for a member by the name of Clinebarger to answer. He owns a transmission rebuilding shop as far as I know.

 

[clinebarger]

Locked Intermediate Sprag or Roller Clutch (Depending what type Direct Drum you have) is what it sounds like. The Sprag/Roller Clutch HAS to overrun in Direct/3rd gear.

 

[JimPghPA]

Originally Posted By: n4ue
Hi to all. I love this site and learned a lot.
This might be wordy, so PLEASE bear with me....

I have a very strange issue and wanted to touch base with any TH400 experts out there.....
I've been a drag racer for decades and at the present, I have a TH400 in my pro street car. I actually have 2 complete spare TH400s. As a drag racer, I never broke the internals, just the case, when I broke a drive shaft. Just mentioning this, because I've 'freshened' up a few.

The car has a TH400 that has worked perfectly for MANY years, but only gets about 200 miles/year. Last week, I made the mistake of using some 20 year old "Nitro octane booster". It made the car almost undriveable. As I was limping home, I saw a huge cloud of smoke from the passenger side of the engine. I cut the fuel pump immediately. At the same instant, it felt like the rear end locked up.
A braided fuel line had ruptured inside (9 psi) and this 'fuel' landed on the header.
After refurbing the fuel system, I have this weird problem:
(The TH has a manual valve body (reverse) and a trans brake, with a 5500 rpm converter.)
The 1-2 shift is great as usual, but when I do the 2-3 shift, it feels like the transmission is almost locking up! With the converter I use, I can normally downshift from 3-2-1-N at pretty much any speed.

I just cannot connect the fuel issue with the transmission issue.
The TH goes into Park, Reverse, Neutral, First, and Second gear perfectly. Fluid is clean, and full. I've always used a large cooler with all my TH400s.

Any thoughts???

Thank You!!!!

ron


You can not connect the fuel issue with the transmission issue because there is no connection. It just happened to happen at the same time.

 

[n4ue]

Sir, thank you VERY much for your reply! I knew (?) it had to be after the torque converter. I was going to pull the pan and check the valve body this weekend.
I haven't been inside one of these for 20 years. I have several 'how to' books and a video by Darryl Russell.
One of my 'spares', is an almost new TCI unit I bought NEW at Jegs. I only made a couple of passes on it, but I pulled it because the large o-ring for the pump was cut and it leaked fluid.

One last question I have..... I'm going to pull the TCI apart before I install it. (been sitting for 20 years in my shop). Do you use the red Vasoline looking assembly grease or just soak the clutches? What type of refresh kit should I buy? Do you sell something I could purchase?

THANK YOU again!

Oh, to the other replier, I'm a retired Engineer, although I'm an EE, I know the chances of a double mechanical failure, at the same instant, in two completely different systems. After all, that hot fuel did soak my trans-brake......
ron

 

[n4ue]

Sorry, senior moment. The video is not by Darryl Russell. He was the chap hurt in a dragster accident in England.....

ron

 

[clinebarger]

Originally Posted By: n4ue
Sir, thank you VERY much for your reply! I knew (?) it had to be after the torque converter. I was going to pull the pan and check the valve body this weekend.
I haven't been inside one of these for 20 years. I have several 'how to' books and a video by Darryl Russell.
One of my 'spares', is an almost new TCI unit I bought NEW at Jegs. I only made a couple of passes on it, but I pulled it because the large o-ring for the pump was cut and it leaked fluid.

One last question I have..... I'm going to pull the TCI apart before I install it. (been sitting for 20 years in my shop). Do you use the red Vasoline looking assembly grease or just soak the clutches? What type of refresh kit should I buy? Do you sell something I could purchase?

THANK YOU again!

Oh, to the other replier, I'm a retired Engineer, although I'm an EE, I know the chances of a double mechanical failure, at the same instant, in two completely different systems. After all, that hot fuel did soak my trans-brake......
ron


How fast were you going when you cut the fuel? Killing the engine or putting the trans in neutral at speed can kill the Intermediate Sprag/Roller Clutch, The Direct Drum is splined to the Sun Gear Shaft. Without the Direct or Intermediate clutches engaged......The drive shaft will spin the Direct Drum up to astronomical speeds especially in a "Low Geared" drag car.


I use Red SPX Trans-Gel to lube seals, o-rings, rings etc during assembly, Soak your frictions in whatever ATF your going to run for at least 30 minutes.

I don't sell parts, I build transmissions. But I will help with part selection, Vendors, & Assembly questions.

 

[Colt45ws]

Sounds like cline connected the trans death to the fuel cut quite nicely.

 

[kc8adu]

thats what i was thinking.
been a while since i had a th400 apart.
never seen sprag failure in one though.just soft parts.

 

[n4ue]

Clinebarger, thank you for the response. I really appreciate your expertise!
I've owned this car for 20 years. Wow! Getting old.

It's been 9.89 sec / 1/4 mile. It weighs 3000 lbs. It's been a great 80 year old car and almost too much fun to drive. I doubt it gets 200 miles a year. No speedo. I've been through the engine a couple of times and swapped rear gears a lot, but this is the trans I bought it with. Currently using 4:11, but have 4:88 and 5:13 gears. I think I mentioned it has a reverse, manual valve body and a trans brake. The shifts have always been superb. I have a large oil cooler and it always runs very cool.
As I make plans to pull the trans, I've been going over the failure in my small mind. The day it failed, I was near home and that 'bad' gas was making the car surge so bad, it was almost undriveable.

With that 5500 rpm converter, there is no braking under down shifts. I ONLY do this at very low speeds approaching a stop. Always used Type F, but I 'think' I put the TCI or B&M race fluid in it when it was new. Your thoughts?

I have 2 spares. While I'm awaiting my trans jack, I'm going to disassemble the TCI unit I went through many, many moons ago. I remember it having the 34 element sprag. When I lived in Ky, we had a trans shop in town that sold hard parts. Here in the 'woods' of N. Florida, nothing, I'd have to go to Jax or Gainesville.
If (big IF), I were to find a good shop in the 'big city', and carried the 'good' trans in for a refresh, what would be a good price?
I don't want to do this trans pull too many times. ha ha

Thank you again!!!

ron

 

[clinebarger]

I charge $250 to refresh a carry-in 3 speed plus parts cost, If the torque converter needs to be cut, cleaned, & inspected that's extra.

A 34 Element Sprag would be a nice upgrade if you have a Roller Clutch now, Make sure a Spiro-Lock Sprag retainer gets used if not already present.

I use Dexron 3 spec fluid in all TH400's because all my testing was done with Dex 3, Nothing wrong with Type F though.