91 Suburban 3/4 ton 4wd No Reverse

[dksob81]

my father in law has a 91 Chevy Suburban 3/4 ton 4WD w/ a 4L80E tranny.
He replaced the tranny filter and fluid and now it has no reverse, it shifts fine through all the other gears but has no reverse. Worked fine before he did the tranny filter and fluid.

[MT-2500]

Originally Posted by dksob81

my father in law has a 91 Chevy Suburban 3/4 ton 4WD w/ a 4L80E tranny.
He replaced the tranny filter and fluid and now it has no reverse, it shifts fine through all the other gears but has no reverse. Worked fine before he did the tranny filter and fluid.

Confirm the transmission is full of fluid whenit is good and hot engine running in park and up to crosshatch on transmission filler dip stick.
If so.
Tell him to drop the pan and check filter applacation for right filter and check the suction tube O rings/seals on filter and fluid pick up pipe.
May have wrong filter or pickup pipe seal leaking or missing.

Let us know what he finds there.

[dksob81]

I actually dropped the pan last night to make sure he didn't knock anything loose. And I didn't see anything, the filter is correct (looks exactly like the old one), the seal was replaced with the filter.

I put everything back together with new tranny pan gasket, filled the trans, test drive for 5 miles, tranny shifted fine but still no reverse, double checked fluid, the level is perfect (about 3/4 up the crosshatch).

[MT-2500]

Originally Posted by dksob81

I actually dropped the pan last night to make sure he didn't knock anything loose. And I didn't see anything, the filter is correct (looks exactly like the old one), the seal was replaced with the filter.

I put everything back together with new tranny pan gasket, filled the trans, test drive for 5 miles, tranny shifted fine but still no reverse, double checked fluid, the level is perfect (about 3/4 up the crosshatch).

You might run a pressure check on transmission pressur.
But if it was working good before filter change I would still suspect filter or pickup seal.
Double check it and also make sure the new filter is not stopper up.
Also shift 4W transfer case around to different gears.
I have had a transfer case knock out reverse.
Good Luck
And let us know how it goes.