th350 transmission please help

[85WorkTruckDeluxe]

hello my buddy has a 76 scottsdale LWB 350 th350 combo the transmission shakes the whole truck in park, neutral, drive and reverse it also shifts late and hard and refuses to let the truck go faster than 55mph above 55 you can step on the gas as much as you want but the engine will just free spin, the shakeing smooths out a little around 1500-2000 rpm but dosen't completly go away. the torque converter bolts are not missing or broken we changed the fluid and filter and there were no metal shaveings in the bottom of the pan. its got me stumped any help will be greatly appreciated

[enaberif]

Originally Posted by 85WorkTruckDeluxe

hello my buddy has a 76 scottsdale LWB 350 th350 combo the transmission shakes the whole truck in park, neutral, drive and reverse it also shifts late and hard and refuses to let the truck go faster than 55mph above 55 you can step on the gas as much as you want but the engine will just free spin, the shakeing smooths out a little around 1500-2000 rpm but dosen't completly go away. the torque converter bolts are not missing or broken we changed the fluid and filter and there were no metal shaveings in the bottom of the pan. its got me stumped any help will be greatly appreciated

Transmission mount and have you ensured your vac modulator is hooked up correctly?

Also look at the governor.

[truckin 79]

Dumb question but are you sure you added enough transmission fluid? If you drained it completely a TH350 will hold about 10-12 quarts.

[85WorkTruckDeluxe]

yes it has plenty of fluid

[85WorkTruckDeluxe]

modulator is hooked up and the mount is good, im new to transmission work could you tell me where the govenor is and how to check it

[enaberif]

Left side of transmission has a cover you pop off.

[85WorkTruckDeluxe]

the govenor might be part of the problem because it shifts late and hard but that wouldn't cause it to shake or not go above 55 would it?

[Drizzle]

Kinda sounds like a rear end problem or torque converter

[cadillac_al]

None of that stuff will make it shake in park. If the whole truck is shaking in park and neutral then it has to be crankshaft/flexplate/torque converter related or very serious internal trans problems. I say it has to come out. If there is no obvious crank or flexplate issues I would rebuild/replace the trans and the converter too just to be safe.

[InitialBoss]

My TH350 is doing the same thing but it's not shaking the truck violently. In park or idle at a stop light the truck will start to shake and I hear a noise near the left side of my truck like the exhaust pipes are tapping something, but they aren't moving. I think my situation may be the same as 85WorkTruckDeluxe. I hope it's something less serious than me taking out the trans. I don't want to spend much on fixing it.

[motornut]

If the block is out of balance (even a broken/cracked fan blade) could make it shake bad

[85WorkTruckDeluxe]

if the block is out of balance wouldn't it get worse at higher rpms though, the higher the rpms the shaking actualy gets better

[motornut]

My 78C Burb broke one of the four blades,went right threw both the master cylinder lines.
If I remember right I think it did smooth out going faster.
If it's wobbly you can prob see it from the side tho.

[85WorkTruckDeluxe]

the engine runs pretty smooth the shakeing is definatly comeing from the trans

[cadillac_al]

Originally Posted by 85WorkTruckDeluxe

the engine runs pretty smooth the shakeing is definatly comeing from the trans

It sounds like the engine isn't shaking much at idle in park? I was starting to think it could be the carb because the only times i have seen engines shake violently is with a carb issue. If you had a flooding carb issue it wouldn't idle well though.

[85WorkTruckDeluxe]

it shakes enough at idle to rattle the windows and when you give it a little gas it feels like its going to shake itself apart but when you get to about 2000 rpm it quiets down a bit but the idle mixture is about as good as its going to get

[InitialBoss]

Did you get this fixed? I may have the same thing going on with my truck, like I mentioned before. Hope you got it sorted out.

[HuntinNut]

Mines pretty much doing the same thing except for it idles smooth untill I put it in gear and then startes the shakes. It also had a knock that we traced to a cracked flexplate. We may be wrong, but we think mine is a combination of the flexplate and torgue converter causing mine. I bought a reman torque convertor and flexplate yesterday so Ill hopefully know something by this weekend. Id say crawl under it and listen while its put into gear. Mine sounded way different from the top than when it did beneath it with it in gear.

[crashz]

Seems like more than one issue. Something is definitely up with that transmission though, and it could be a torque converter problem. I'd try un bolting it, sliding the converter back, and starting the truck. Don't let it run long. If the TC catches the flywheel, that could be bad.