SirRobyn0
Full Access Member
- Joined
- Dec 6, 2019
- Posts
- 6,744
- Reaction score
- 11,332
- Location
- In the woods in Western Washington
- First Name
- Rob
- Truck Year
- 1984
- Truck Model
- C20
- Engine Size
- 305
Seem strange to ask this question on a GM forum, but I know there is a lot of knowledge here, plus I'm not on any other car forums so hopefully someone will be able to help. I know @Matt69olds knows about GM trannies so I'll tag ya hoping you can help. So here the deal this is one of my farm trucks. This is the overdrive auto trans, engine is 3.9 magnum, the only electronic controls on the tranny are for the lockup converter everything else is hydraulic. A few years ago I lost reverse in the tranny and had a local tranny shop rebuild it. Actually it was TRC they are a national tranny co so you may have heard of them.
Anyhow ever since the rebuild I've had trouble with the transmission over speeding the engine. So for example if you start out from a standing stop and floor it, it'll never shift out of first. Well I chickin out at about 6K since the redline on this engine is 4,600. Part throttle it'll shift up just fine. At highway speeds it'll do the same thing. Cruising along step on the gas to hard and you'll be down in 2nd gear with the tach flying up past 6K. Before the rebuilt I'm pretty sure the tranny would shift up at WOT at about 4K. And it certainly never would have shifted down into 2nd at 75MPH. I don't have to push it all the way down to the floor to get this to happen, but pretty close. It will also do this a lower speeds and shift down to first and over speed the engine.
I've had this truck back to the tranny shop 3 times. I've raised hell with them a couple of times, yet the truck still shifts the same, and like I said it's a farm truck so being without it for week at a time while the tranny shop doesn't fix it again it not an option.
The TV cable is adjusted properly. I've slacked it off some and unless I get it to the point where it shifts up really late it still does it.
What do you think? While I'm not a tranny tech, most of you know I am mechanic so I'm at the point where I'd like to try fixing this myself but I just don't know where to start. Thanks.
Anyhow ever since the rebuild I've had trouble with the transmission over speeding the engine. So for example if you start out from a standing stop and floor it, it'll never shift out of first. Well I chickin out at about 6K since the redline on this engine is 4,600. Part throttle it'll shift up just fine. At highway speeds it'll do the same thing. Cruising along step on the gas to hard and you'll be down in 2nd gear with the tach flying up past 6K. Before the rebuilt I'm pretty sure the tranny would shift up at WOT at about 4K. And it certainly never would have shifted down into 2nd at 75MPH. I don't have to push it all the way down to the floor to get this to happen, but pretty close. It will also do this a lower speeds and shift down to first and over speed the engine.
I've had this truck back to the tranny shop 3 times. I've raised hell with them a couple of times, yet the truck still shifts the same, and like I said it's a farm truck so being without it for week at a time while the tranny shop doesn't fix it again it not an option.
The TV cable is adjusted properly. I've slacked it off some and unless I get it to the point where it shifts up really late it still does it.
What do you think? While I'm not a tranny tech, most of you know I am mechanic so I'm at the point where I'd like to try fixing this myself but I just don't know where to start. Thanks.
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