TH400 no 2nd gear, sprag or clutch pack...?

[folkenheath]

I have a TH400 I built about 2 years ago. Pretty standard performance build, alto clutches, 4 int clutches, 34 element sprag, dual feed direct clutches, HD bands, HD snap ring, all new bushings and bearings, etc.

Anyway, it only has about 2k miles on it over the past two years, and 2nd gear stopped working, it will pretty much act like it is still in 1st gear (when in 2nd gear), but you can tell something is free revving. 1st and 3rd work perfectly normal. I see that the int clutch is still applied in 3rd gear, but does it really do anything since the int sprag is overrun then anyway? If this is the int clutch, would I still have 3rd gear?

I am asking because it is driving my nuts, and I won't even have time to drop the pan for 3 - 4 weeks. If it's the sprag, it is what it is, if it's the clutch pack, then I willl need to figure out why the clutch pack wouldn't hold.

Just trying to diagnose the symptoms since I can't dig into it for a little while.

Thanks.

 

[SSedan64]

3rd would still be there but, would have less holding capacity without Intermediate clutch, Dual Fed Dir. would be a + also..
The InteM. Roller/Sprag is holding in Manual 2nd & Drive 2nd so that may be the problem.

 

[folkenheath]

Thanks, I am leaning towards the sprag, because I don't see how 4 alto red clutches can't hold in the pack. And I did use the wave plate and the HD snap ring, so I should not be busting case lugs. However, it won't hold in manual 2nd either, so I may have burned up the int band if it is the sprag. However, engine braking in 2nd still works, so that's confusing. I guess we can only speculate until I have time to tear it apart.

But I still think that the int clutches can't do anything in 3rd gear if the sprag is being overrun, it just seems like they are there for a hydraulic reason and they wouldn't hold anything....

Also, I just realized there is a transmission forum, sorry I put this in the wrong one.

 

[malibu795]

3rd gear all 3 clutches are on... if is one is weak...forwad or intermedaite(2nd), 3rd would be as weak as 2nd...

lost a hard part
i was fight direct clutch burn up for a while (th400)... found out it was the seperator plate that was restricting oil pressure to the DC had to trace out the fluid power paths... that was a PITA it now has red eagles and kolene steels

 

[folkenheath]

Did you dual feed the direct clutches? That about doubles the apply area for the direct clutch, increasing high gear torque capacity, and it's pretty much free. You probably already know that.

Also, I agree all 3 clutches are on in 3rd gear, but if I am not mistaken the intermediate clutch only holds the sprag, to stop the drum for 2nd gear. But in 3rd gear the direct drum applies and is then overrunning the sprag, so if the int clutches let the sprag go, it wouldn't matter would it, because it's free spinning anyway? However if the int clutch hyd pressure was lost, then other circuits would lose pressure too, and that would lead to more problems I would think.

And thanks for the info, I do think it's probably the sprag too. I'll let you guys know what I find out when I tear it apart in a few weeks.

 

[folkenheath]

I know this is an old thread, but I realized I never replied and I am just following up so that others can avoid it. I don't like searching to find threads with the exact question I am looking for and then having no answer at the end.

I did roll the sprag, and since I kept driving it and using manual 2nd I then burnt up the intermediate band. So if your TH400 acts like it's still in 1st when you shift to 2nd, and 3rd still works, it's most likely the int sprag(or roller clutch if you have one).

The reason the sprag went out was incorrect machining. I bought a reman unit from a trans supply shop and assumed it was good, it wasn't. Minimum OD for the sprag race on the drum is 3.159", no tolerance below that, mine measured between 3.155 and 3.157, so it was too small and also out of round.

 

[SSedan64]

Yikes! :shock: I agree with you, that's what did in the Sprag.
Glad you got it figured out.

Todd