transmission doesnt shift

[OLD chevy]

hey, new to this website but jsut bought a m1009 and everything but the transmission is fine.. ive been looking around this website and ive seen theres alot of posts about this, what ive done so far to figure this problem out is rip the **** tranny out. had another t400 to put in but dident realize untill i got the tranny out of the truck that it was a t400hd.. now im stuck, dont know what todo, ive seen theres things about a vacum line or filters but i thought id just throw the one i knew was good in but that obv dident work, ive been wondering if i should get a rebuild kit or get one from a junkyard? called up a few places and they want 1200 to rebuild it 4 me, so screw that. its eaither i put the old one back in try the new filter and see if the vacums screwed up to hopefully fix it or rebuild or junkyard tranny for 450? what do u guys think i should do? tranns deff screwed up would not shift unless i pedel shiffted and truck ojnly has 90k on it so idk... thanks in advance

 

[Cucvnut]

hmm you sure its the transmission and not the vacuum pump ? nothing is wrong with a HD th400. me and combat jump just rebuilt his in his garage for around 500 to 600 bucks. its very doable if you have time and are willing to try.

 

[edpdx]

Check to see if the transmission modulator is connected and the hose is sound. You need to probably post more info on what is happening. Not shifting to 2nd from low? Not going into any gear? Won't move in drive or Reverse?

 

[dependable]

Would recommend changing filter & fluid. This has never been done on many of these trucks, and the filters clog, especially when they sit. Try this before rebuild.

 

[Warthog]

Just about any shop will do a bench rebuild for $500. The big cost for them is the removal and installation. Since you have it out already, go ahead and rebuild it. Not that hard to do yourself if you are up to it. There are many videos on Youtube showing how to rebuild the TH400. One of the easiest out there.

 

[OLD chevy]

yeah im prob gunna throw it back in, change out the filter and check to vacum lines, it does sound like that could just be the problem, but other than that i like the idea of a rebuild, never done one before but am willing to try if it comes down to it, ive just heard that their a pain to rebuild but if u guys say its not that hard as long as u have general knowlege on working with cars and trucks lol, aint like im mechanically inclined, but tranny jus wont shift on its own, i can get her to shift but its a pain, hopefully the filter works out... thanks for the help

 

[suggsdr]

Check all rubber hoses on the vacum lines its all 25 years old.I had trouble shifting from 2-3 lines were leaking.put new lines runs like new now good luck.

 

[WARWAG]

Replace all vacuum lines first. If it drives but doesnt shift out of first gear then its that or the modulator. The hoses will cost you a few bucks and will need to be changed regardless of what ever the actual problem is. The Modulator I believe is about $85. Change that next. Then change all of the fluid and filter. It will be one of those three things. I would say the chances of needing a rebuild is about 5%. Good luck and post pics of what you find wrong!

 

[epitts]

Mine needed a new vacuum pump and a new vacuum valve on the IP. New vacuum line and it shifts just fine now.