4l80e no reverse

[amazinblaze]

i have a 1991 k2500 recently my reverse went out it has a initial shudder when you put it into reverse then nothing its like fluid pressure i can rev it up dangerously and it will go in once its in its in the warmer it gets the better it gets i have changed alla the electronics on the trans wiring harnesses included ive pulled the valve body the plate holes for the check balls was worn badly i replaced the plate with a new one took all the valves outta the valve body and cleaned it good pulled pressure regulator outta pump replaced seals on reverse servo naturally i checked the band its not broken i even changed the tps there was nothing in the pan initially when i took it off just sedimate but like i say ive cleaned everything i even air pressure checked everything. the force motor they give me is a black one supposed to superceed the silver one the new plate omited the hole for the old one and i had to drill an additional hole in the valve body for pressure relief transgo 48-plt-o1 any advice would really be appreciated as this thing is making me go bald scott

 

[toddlnrd]

I had the same thing happen to me on Friday night. It had been shuttering in reverse for some time after the September 2007 rebuild, then Friday no reverse at all. Took it to the tranny place today. He said it was the SUN GEAR SHELL that went bad. Apparently, these sun gear shells go bad on the GM trucks. I only have 33,000 miles on my rebuild when mine went out. Someone has come out with a new Sun Gear Shell called the "beast". It is supposed to be 3x stronger than the previous "stock" ones.

It is going to cost me another $1000 to get the "beast" installed.

Todd

 

[racedaymechanic]

I went thru this a couple weeks ago on my 4L80, I Had no reverse and No Decel in Low, I took the servo out and get the pin off of the Piston and then on the end that points up I Took the rod to work and Tigged it up about .250 I put it in the lathe and turned it down to size the total length increase was .200 after machining I put a slight crown on the end to match the factory end, Put it all back together after work today, And IT WORKS GREAT!!!!! solid shifts up thru and strong Reverse now