TH400 Rebuild complete. No reverse...

[flewbyu]

Just finished complete rebuild of 1009 tranny. Went to test and, no reverse. Doesn't even feel like it is picking up the clutches. REALLY hate to pull this thing again...Do the experts have experience in something simple to check? BTW, forward works great, stronger than when I got the truck. The first (nearest TC) set of clutches were completely wiped.

 

[4bogginchevys]

Linkage??? sorry to say.... Sounds like valve body issue, I made a call to be sure! good luck!

 

[tm america]

does it have third? did you change the low-rev band?if so did you check the band clearance? also check the check ball location you have to have the one in the bathtub at the rear and the one all the way to the front that is inline with the bathtub.you could have ripped the seal on the low-rev servo did you air check everything when you put it together?check those things out and let me know what you find i have also seen the pins walk out of the case for the low-rev band

 

[tm america]

or you could have put the low- rev sprag in backwards hard to do but it can be done .if you have third i would jack it up pull the valve body air check the low-rev servo and go from there

 

[flewbyu]

Directions for air check? Is it in the TM?

 

[tm america]

no basic trans rebuilding. how is third ?does it have engine braking when in low?

 

[tm america]

you have to take your blow gun and put air into the feed hole for the low-rev servo it is the hole just behind the bathtub where the check ball goes also you should air check the intermediate cluches and direct clutches the int is fed through the center support bolt the dir is the hole to the left or right of the center support bolt and the forwards is one of the holes that are near the pump but hard to tell you which on with out drawing you a pic

 

[flewbyu]

Haven't driven it fast enough (stayed in neighborhood) to get third. First is great...noticed when assembling that plastic piston has a small gouge in it, although the flat ring on it is unmolested...
I didn't pull apart anything deeper than the intermediate clutch piston.
How do you keep the check balls in place when pulling valve body in vehicle? I'm sure they are correct now, but they will fall in VB is removed in truck. Have diagram and can replace, but not sure if grease to hold them in place will hurt anything.
Thanks for all the help thus far.

 

[tm america]

did you install all three seals in the direct drum if you leave the center seal out or one of the sealing rings on the center support without plugging the hole in the plate you wont have rev either there is probably 20 things you could have done wrong you have to let me know how third is and if you have engine braking in low for me to be able to tell you where to look

 

[tm america]

go drive it i cant help you unless you know how third is and if it has engine braking in third it could be a problem with the band or the dir clutch but cant say without knowing how it drives you wont mess anything up roadtesting it.and you use trans gel to hold the check balls where they should be put them on the plate with a little trans gel.then put the plate up hold it up with the kick down solonoid and bolts then put the valve body back up

 

[tm america]

the plastic piston is the second acc.piston and should be replaced with a aluminum piston anytime you rebuild one the plastic one crack all the time and will make the int. burn up and since you didnt tear in down all the way its a good chance the low -rev band is burnt up or broke , did it have rev before you worked on it?

 

[flewbyu]

Will drive tomorrow and get back to you. Used original band. It was not flaky, pitted or chunked. No discoloration.
Got both sealing rings on inter apply piston, real PITA. Used feeler gauge to seat seals.
BUT, no, reverse slipped really bad before, hence the rebuild attempt.
Thanks again.

 

[tm america]

ok drive it in drive and then manually through the gears and the band you are looking at was the int band .it goes in after the int.clutches it is a single wrap band about one and a 1/4 inches wide the low -rev band is a triple wrap band and goes in before the center support but you didnt tear the trans down far enough to see if it was good if you didnt take the center support out the int band is only there to give you engine braking in manual second it keeps the int sprag from overrunning but it has nothing to do with rev.

 

[SsjSned]

although i have all the TM's i bought a dvd to help me with fixxing my tranny. worth buying for me since i knew nothing about the TH400 it goes threw everything. heres a link to the guys site who made it but if i recall i bought my copy off ebay
hope u fix ur tranny man. good luck
General Motors -GM- Turbo Hydramatic 400 Automatic 3 Speed Transmission Rebuild DVD

 

[flewbyu]

OK. Got it all torn down (AGAIN) all the way to the rear band. Its WIPED. Parts on order, thanks for all the help, I really appreciate it. Should I worry about the hard parts? They all look pretty good with minimum galling and no discoloration...

 

[tm america]

ok here it is there is two ways to do a trans the right way and the other is to keep doing it over and over again .so yes you need to worry about the hard parts unless you like to rip it out for practice.i could write a book on what you need to look for but i willl just touch on the most common problem areas. first check the planets for wobble second any bushings with any wear need to be changed it it real important that everything turns true and straight. so change the center suport bushing ,pump bushing and tail bushing even if they look good they are critical. all clearences must be right on allow about .015 inch clearence for each clutch and air check everything if something is leaking air it will leak pressure and burn up make sure you check the pump out real good it should have .001-.002 clearence anymore and you will not be making pressure like it should . last you need to check end play on the rear up to the center support should be about .010-.015 then check end play at the front it should be .010-.020 any less and it will fry the thrust washers any more and sealing right wont seal up right this is just the beginning if it looks worn change it .if it gives off metal it will maker the gov stick and you will have to go back in do it right do it once

 

[flewbyu]

Oh, I do enjoy ripping it out...getting pretty good at it, too. Thanks for all your help TM.

 

[tm america]

mabye i can sell you a wing nut kit for your truck if you,re injterested let me know if you have anymore questions pm me i will give you my number it will make it easier on us

 

[flewbyu]

They make those?!?:-d