Backed off the trailer okay, but sometime during the day I lost reverse. I only used the transbrake for the first run and it worked fine. I don't think I used reverse for the rest of the day until run 6 when I discovered that there was none. I wasn't smart enough to see if the t-brake would engage reverse. Trans has 46 runs since last rebuild. Does the trans have to come out or is it possible to put a manual VB in to get through the season? Thanks

What valve body are you running?

Transbrake engages and holds the car, but won't back up in manual selected reverse position?

Try the TB. Put a pressure gauge on before you pull it. Reverse section might have lost seal.

quote:

Originally posted by Eman:
Try the TB. Put a pressure gauge on before you pull it. Reverse section might have lost seal.

Reverse has to apply to hold the car on the brake.

quote:

Originally posted by Eman:
Try the TB. Put a pressure gauge on before you pull it. Reverse section might have lost seal.

Should I run a pressure gauge in the car? I don't think I've ever seen one but people talk about trans pressure whenever there's a trans problem and I see small gauges available. 300 psi of 180 degree atf in the car could be frightening if a leak ever occurred though. I'm leaning toward just getting the tool type gauge unless down track numbers are better.

quote:

Originally posted by Goob:

quote:

Originally posted by Eman:
Try the TB. Put a pressure gauge on before you pull it. Reverse section might have lost seal.

Reverse has to apply to hold the car on the brake.

I'm not sure if the brake works. I need to test it but it's a little sketchy on the trailer in the garage, but I think I'll try it tomorrow. Not sure who's brake this builder used. It's not a pro brake.

quote:

Originally posted by Goob:

quote:

Originally posted by Eman:
Try the TB. Put a pressure gauge on before you pull it. Reverse section might have lost seal.

Reverse has to apply to hold the car on the brake.

That's why I said try the TB.

As for a pressure gauge I don't mean going down the track. my trans pressure gauge has a long hose so I can read it from the drivers seat. What you want is a pressure reading standing still. I can't remember if or where a T400 has a port for reverse pressure. Might do the google for diagram of which port is what. I haven't seen the inside of a T400 in decades but I think reverse is a band apply.

This message has been edited. Last edited by: Eman,

I ordered an OTC gauge and the t-brake holds the car, at least on the trailer with very low rpm and everything cold. Also, I made a pass right after I learned that I had no R and all 3 gears worked fine, if that means anything.

I'm gonna need direction on how to test. I only know of one port on a 400, driver's side near the shift lever I think. I need to know things like fluid temp, rpm, which gear or gears and parameters.

quote:

Originally posted by Ron Gusack:
I ordered an OTC gauge and the t-brake holds the car, at least on the trailer with very low rpm and everything cold. Also, I made a pass right after I learned that I had no R and all 3 gears worked fine, if that means anything.

I'm gonna need direction on how to test. I only know of one port on a 400, driver's side near the shift lever I think. I need to know things like fluid temp, rpm, which gear or gears and parameters.

Something in the back of my limited brain keeps recalling something very minor that can go wrong with the manual valve linkage, in some transmissions.....damn old age and forgetful.

You should be able to select R or N on the shifter and engage the t-brake to back up, then figure out why you can't manually select it.

My T-400 with a Hughes Reverse Manual VB with Brake will engage reverse if I put the selector in Neutral and push the button.
If yours will hold the car, I believe there is a decent chance that you won't have to pull the trans.
Like Dave / Goob was saying, it may be in the manual valve area, if you drop the pan, look around near the Rooster Comb (manual selector shaft area). I have the same CRS fuzzy recollection that Dave has, and think I got by fairly easily with whatever the fix was, but that was 20 years ago... Best bet would be to check the pressure first though, before tearing into it.

quote:

Originally posted by Goob:

quote:

Originally posted by Ron Gusack:
I ordered an OTC gauge and the t-brake holds the car, at least on the trailer with very low rpm and everything cold. Also, I made a pass right after I learned that I had no R and all 3 gears worked fine, if that means anything.

I'm gonna need direction on how to test. I only know of one port on a 400, driver's side near the shift lever I think. I need to know things like fluid temp, rpm, which gear or gears and parameters.

Something in the back of my limited brain keeps recalling something very minor that can go wrong with the manual valve linkage, in some transmissions.....damn old age and forgetful.

You should be able to select R or N on the shifter and engage the t-brake to back up, then figure out why you can't manually select it.

I pushed the button with it in N and it doesn't go into R, but I don't think it ever did. I thought only the pro brakes did that. I don't think I pushed the button with the shifter in R. I can try that tomorrow.

I have a TH400 that's been sitting on a table partially disassembled in my garage for at least 10 years now that does the same thing. Took it apart and put it back together twice and could not get it working properly.

Decided to go with a powerglide and never looked back. The TH400 would have been nice but I don't really need the extra gear.

quote:

Originally posted by Ron Gusack:

quote:

Originally posted by Goob:

quote:

Originally posted by Ron Gusack:
I ordered an OTC gauge and the t-brake holds the car, at least on the trailer with very low rpm and everything cold. Also, I made a pass right after I learned that I had no R and all 3 gears worked fine, if that means anything.

I'm gonna need direction on how to test. I only know of one port on a 400, driver's side near the shift lever I think. I need to know things like fluid temp, rpm, which gear or gears and parameters.

Something in the back of my limited brain keeps recalling something very minor that can go wrong with the manual valve linkage, in some transmissions.....damn old age and forgetful.

You should be able to select R or N on the shifter and engage the t-brake to back up, then figure out why you can't manually select it.

I pushed the button with it in N and it doesn't go into R, but I don't think it ever did. I thought only the pro brakes did that. I don't think I pushed the button with the shifter in R. I can try that tomorrow.

Now I'm going to have to check mine to see what it does. Vintage 2001-ish Coan standard brake.

quote:

Originally posted by AlkyIROC:
I have a TH400 that's been sitting on a table partially disassembled in my garage for at least 10 years now that does the same thing. Took it apart and put it back together twice and could not get it working properly.

Decided to go with a powerglide and never looked back. The TH400 would have been nice but I don't really need the extra gear.

A Kilgore 2.10 / 1.40 gear set would change your life.

https://www.tciauto.com/trans-line-pressure
Link to line pressure chart

quote:

Originally posted by Eman:
https://www.tciauto.com/trans-line-pressure
Link to line pressure chart

Much better than the charts I've seen, thanks for the link. I might even be able to remember the pressures for each point, lol!

Here's the numbers @ 2000 rpm cause that's what Eman's chart said to test at.
P-190
R-150
N-190
1-190
2-200
3-200
Only 150 line psi in R, 190-200 everywhere else. I couldn't fill a thimble with my internal transmission knowledge so unless I see something obvious after pulling the pan, I'll have to yank it. I was hoping to not have to pull it out but even if I take the servo apart, I won't know what I'm looking at. I don't know how a brake works but it seems like the band would have to be okay if it holds when the button pushed. I'm gonna check to see if maybe my shifter cable needs adjusting, like maybe I'm not all the way in R. This trans has less than 50 runs on it.

This message has been edited. Last edited by: Ron Gusack,

Just to verify, my Coan standard brake does reverse when neutral is selected and the brake is engaged.

I can't help you with what the pressures mean.

It doesn't make sense that the brake will hold the car but not back up.

What if the servo wasn't sealed properly and leaking fluid causing a pressure drop or does the brake use the servo too making that theory no good?

I talked to the company that built the trans, but not the owner. The guy I talked to basically said it was most likely an out of adjustment shifter and didn't seem to hear me say that I checked it and it was fine.

The other thing this trans has always done is push lots of atf out the vent tube. I've had 2 rebuilds and asked to make sure that the vent tube issue be fixed, but it doesn't happen. I'm surprised at how many trans shops in the area don't have a dyno to check pressures and such. I'm close to buying an aftermarket case from someone with a dyno and hoping for success.

Wow, you have trans supplier problems for sure.

Mine has never lost a drop of fluid from anywhere, let alone pushed any out the vent.

I still think there's something to the manual valve linkage, not related to the shifter that can be wrong, like a S hook link out of place or something that will cause problems......

Call Dan Dishon at Dishon Transmission in Logansport, IN., he's good about talking to folks and getting to the problem.