tranny issues

[oldstyle69]

I have a question. First of all I am new to the board this is a great site. I picked up a 72 seirra granda last night. I love it. It is very soild for a Iowa truck. I do not have much history on it but it looks to be about a 10 year old restore. 400 motor 400 turbo, posi, factory air, tilt rallys,tach. I got it running tonight it had been sitting for a couple of years. It runs very nice but the tranny is sluggish going into reverse. When it does engage it slips. It seems to 75% of the time miss first gear completely. Starts in second gear. What do you guys think? I was thinking maybe some stick Valves in the body. Is there a quick fix? has anyone ran into this issue before.

[Wrenchbender Ret]

About all you can do is change the fluid & filter. Pull the vacuum hose off the modulator & make sure there is no fuid in it. If that doesn't help it it is time for a rebuild.

[GMCJOE]

x2 and in addition change the pump.

[gmachinz]

If it's sat a lot of the time with a fairly fresh trans overhaul to begin with-it may be youhave some debris or some dry spots in the housing of the modulator valve. If reverse is ok chances are it's not a worn 1st gear synchro set since on TH400's 1st and reverse share the same ones, you might want to pull the cover off the modulator valve and pull it out-take a lint free cloth soaked in transmission fluid and completely wipe the interior of the housing out and re-install the modulator valve-that might help...if that doesn't make a difference, try adjusting (if it's an adjustable type) the vacuum modulator itself-clockwise lowers the shift point and counterclockwise raises/delays the shift point.

[oldstyle69]

Hey Thanks guys. First is strong but some times skips from a dead stop after you drive it for a bit and goes strait to 2. Reverse slips and locks in after a bit always. Its crazy you can shift to second gear out of drive and it will hold but if you go to 1 out of second it will shift to 3 gear I put some lucus in it and it seems a little better but I will try to clean it up this weekend.

[oklalawnboy]

I didn't think the 400 had a modulator. It does have a governor though that could be sticking or a tooth or two broke.

[oldstyle69]

Where is the governor located and whats it look like.

[oklalawnboy]

If I'm not mistaken, it is on the passenger side about in the middle. Round cover with a spring holding it on. Got to thinking though, The governor may only effect shifting. I had one break because it sat long enough for rust to form on the upper half of the output shaft. (oil level in tranny only covers half the shaft when sitting still) After driving it the vibration from from the governor jumping over the rust finally broke a tooth. This probably doesn't help you at all. sorry.