A440F Transmission issues (1 Viewer)

[RocketCityCrzrs]

I'll try to keep it simple, but i made the horrible HORRIBLE mistake of letting aamco do a tranny rebuild for me 2 years ago and have nothing but issues since. I have been, since, using Nance Transmission and have really enjoyed their support, but the trans still isn't right. When the truck is cold and it shifts from 4th to lockup the truck feels like you are driving over those idiot sleep bumps on the side of the road. Very fast violent vibration that shakes the whole truck. If i let off the gas and then try to accelerate about 70% of the time it stops. if i try to accelerate while it is vibrating, it gets worse. After the truck runs for about 15-20 minutes, it stops and usually won't do it again until cold start the next morning.
I have had Nance put a new lockup cylinder on it, and a new torque converter. He has also gone through the valve body and said all of the valves seem to be in working order. Our recent discussion he thinks that a valve maybe sticking when it is cold but isn't sure.
I have spent stupid $$ trying to get this corrected and am just at the point to put a reman in it, but i can't find any reputable brands that sell them. I have also looked at doing the 5speed route, but i don't like that option due to the short clutch throw that the truck would have since the seat is so damn close to the firewall.

Thoughts??

 

[MacGYVER1979]

shot in the dark, if it only happens when cold it may be an ATF viscosity issue?
Maybe a good flush and higher quality ATF?

 

[RocketCityCrzrs]

Not a bad idea, use a good AMSOIL?

 

[MacGYVER1979]

this video is a great flush procedure.

as far as the best ATF for our transmissions, Bob Is The Oil Guy | The Internet's Number One Motor Oil Site

 

[bentonrover]

Definitely what I was thinking. Better quality fluid will make a difference. Especially on a rebuilt or new tranny.

 

[MacGYVER1979]

Making a transmission firmer by changing the fluid | ATF, Differential, Trans, Brakes, P/S | Bob Is The Oil Guy
this is what the oil experts say about our trans and ATF

 

[RocketCityCrzrs]

Great advice guys. This is a great place to start. I have also contacted ACC in atlanta about a heavy duty valve body. I would much rather just do a fluid change on what i have and alleviate the problem though.

 

[RocketCityCrzrs]

Let me ask a dumb question guys, wouldn't a viscosity issue present itself more when it is warm vs cold? I would think the fluid would be more viscous when cold.