TH350 reverse problem

[Joe-NC]

I have a TH350 on an '84 Silverado that barely moves in reverse until the engine has been warmed up completely and driven a little. The fluid is new/clean and the level is fine. The forward gears change just fine, couldn't be smoother. I haven't checked the filter. I've only had it a few months.

I've read other posts about others having the same problem, but there was no good resolution other than recommendations on changing the filter. Surely there is a straightforward, common cause for this symptom? Any suggestions?

Coincidentally (don't know if this is related): There is a roaring that I haven't been able to pin down yet. It gets louder/higher pitched with increasing speed, then quiets down when I drive a constant speed, and goes away when I'm slowing down. Sounds like its coming from underneath where the cab meets the bed. I can't decide if its the transmission or rear end.

Also, the speedo is way off (I'm going about 10mph faster than it shows) so maybe someone has put in a different rear end?

 

[velojym]

Last time I heard anything that fit that description, I had to buy a new (well, a really nice used) rear end. (the noise anyway... not speaking to the other symptoms)

[bobcooter]

I was having the same problem with my TH-400 on cold mornings. It did not want to back up. I pulled the pan and saved my old fluid. I changed the filter. Then I added two jugs of Lucas Transmission Fix. I then filtered my old fluid and topped of my trans with that. I have put around 5 or 6, 000 miles since then with no problems. It does not slip even in the coldest weather we've had which was in the low 20's.
http://www.lucasoil.com/products/display_products.sd?iid=29&catid=9&loc=show&headTitle= - Lucas Transmission Fix

I'm not saying it will work for you, but it worked for me...

[Joe-NC]

Thanks for the advice.  Others have said the same thing, so that's what I'm planning to try. Strange that so many people have this same problem, but no one seems to know WHY. Transmissions must really be mysterious creatures.

[bobcooter]

I had a guy tell me that there is a valve inside that has to switch and sometimes they start sticking.

[VileZambonie]

Start with a pressure test.

[sbx22]

I'm having the same issues with my TH350 in my 74. Forward gears couldn't work any better, but reverse is having issues. The transmission pan is leaking, I've had it replaced twice within the last couple years now and lose fluid from time to time. I just top it off. Should I just get another tranny? It's not sealing right.

[bobcooter]

If you take it off again, eyeball it make sure all of the sealing edges are straight. You may have to put it on a flat piece of steel or work bench and tap the dimples around the holes out with a small ball pien hammer.

[VileZambonie]

Your leak is most likely NOT the pan. Check the detent cable where the platic tube and cable meet.

[123 pugsy]

No mystery in trannies.

Old seals when cold are pretty stiff and they probably soften up when the tranny gets warmed up.

I believe the Lucas softens up the old seals and that's what corrects the problem.

[bobcooter]

I think I've put around 8000 miles on it since I added the Lucas and knock on wood, it hasn't burned up yet! Shifting fine. I hate to brag on it too loud. I convinced things like that have ears!