Transmission Problems

[GMC_Utility]

I have a 1996 Grumman step van on a GMC chassis RWD. I am assuming it is a 3500 drive train as the GVW is roughly 14,000 lbs. Starting about a year ago overdrive started slipping then eventually wouldn't engage at all. A couple weeks back 3rd started doing the same thing. Last night reverse stopped working altogether out of nowhere. Since it happened systematically like that, any ideas on what the problem may be? Before I go get raped by a trans shop I was hoping to get an idea of what the problem is. I would rather not drop 3k into a remanufactured trans if i don't have to but will if that is what needs to be done. I love the truck and it runs awesome otherwise(after getting the heads done) Problems started happening at 105k miles and continued till now roughly 115k miles.

[gmtech4]

needs a rebuild from a GM tranny guy or a replacement tranny from the general ,it comes with a 3yr warranty ,cooler flushed and flow rate recorded

 

don't skimp out or it WILL bite you

 

my 2 cents ,( I was a tranny guy,I know)