Slipping on highway

[Hezsus]

Basically I helped my buddy put together a 97 c1500 ecsb, 5.7l with about 320original kms and a bad trans, we put a used trans in it that from the markings was rebuilt 50kms before the doner truck was scrapped.

anyways everything went good aside from that i never changed the rear main seal, it does leak a little bit i think, nothing severe.

anyways he moved out of province for about a month, his old man drove the truck once or twice, when he was back we went for a drive, it would rev up high between shifts, like it was slipping, once in gear it was fine, it seemed to be only in 3rd/4th or mabye 2nd/3rd (his truck shifts at different times than mine (about 5" diference in tire size)

anyways He drove it home and i planned to look at it later on that day, figured fluids or something (he dosent check them like he should).

but now he claims (and i havent seen the truck to know any of this exactly) it wouldnt move at all and now its leaking oil.

so i'm assuming he's lost first gear, and mabye a cooler line blew out and he lost trans fuel, not oil. (hoping). or it could be oil leaking and unrelated to the trans.

Where should I start looking?

I checked here already and sounds like it could be (best case) a leak/pump failure or 1/4 shift solenoid.

http://www.gmt400.com/forum/showthread.php?126-4L60E-Messed-up-Help-Within

http://www.gmt400.com/forum/showthread.php?3596-answer-to-any-4l60e-trouble

any deeper insight is appreciated, i'll keep this post updated for reference until i've got it fixed (or find him a new c1500)

 

[rhino]

I would start making sure it is full of fluid. If it's full, and still won't move, I would go ahead and pull it out and do a teardown. A worn pump could explain low pressure causing it to slide between gears. It would be best to go ahead and disassemble the unit though and check the clutches.

 

[Hezsus]

I would start making sure it is full of fluid. If it's full, and still won't move, I would go ahead and pull it out and do a teardown. A worn pump could explain low pressure causing it to slide between gears. It would be best to go ahead and disassemble the unit though and check the clutches.

Thanks for the info, it looks like i wont be able to get a look at it till later in the weekend, my buddy dosent seem to mind, he's more worried i get the buggy i'm working on done for when hes back home next.
If it does need removed I may just try and find another gmt400 for him, theres only about 1.5k into the truck, and its really nothing special. (plus if he sells it he can pay me for parts)

i'll see what it looks like, can the pump be changed from the pan if it is giving low pressure and I dont wanna open it up?

 

[Hezsus]

So, The truck does move, First and reverse are no problem at all, what its doing is slipping between gears, once its in gear it holds good, just inbetween the gears the engine will rev right up. If i feather/blip the pedal I can get 3rd (ran outta road in town to try 4th)
but 1-2 slipped a little, 2-3 slipped alot.

It was very low on fluid, I added about a quart and it got better, It didnt make a diference if i tried shifting manually and the lower the rpms the better it would engage.
I have not determined the source of the leak, It is external, the trans fluid in the trans (the little that there is) is dark for how long it has been in there (about 5k kms) it looks like 50k.

Is it possible that it simply needs fluid? and the leak fixed? I think thats what i'll try first anyways.

I will have it in my shop tomorrow on the hoist to get a better idea

 

[rhino]

It defiantly sounds like its running low pressure, maybe a pressure control solenoid. I would do a pan drop, if it's full of metal, go ahead and pull it. If it just has dark streaks, thats probably just from the slip and I would try the PCS

 

[Hezsus]

It defiantly sounds like its running low pressure, maybe a pressure control solenoid. I would do a pan drop, if it's full of metal, go ahead and pull it. If it just has dark streaks, thats probably just from the slip and I would try the PCS

Its been a while but last night I got a good look at it, Leaking out of the dipstick tube connection, So i fixed that and filled it up, If anything it has too much fluid now but it still revs high and slips before going into third and 4th gear dosent happen, it just stayin in 3rd right up to redline

Tonight i'm dropping the pan and draining all the fluid, got a new filter and pan gasket. I'll see what kind of condition its in, I let my buddy drive it home last night, hopefully that wont hurt it more if its just a PCS. I'll keep you updated and thanks for all the help.

 

[Hezsus]

Its been a while but last night I got a good look at it, Leaking out of the dipstick tube connection, So i fixed that and filled it up, If anything it has too much fluid now but it still revs high and slips before going into third and 4th gear dosent happen, it just stayin in 3rd right up to redline

Tonight i'm dropping the pan and draining all the fluid, got a new filter and pan gasket. I'll see what kind of condition its in, I let my buddy drive it home last night, hopefully that wont hurt it more if its just a PCS. I'll keep you updated and thanks for all the help.

took the pan off, and there was no chunks of metal but pretty streaky dark fluid and settlings in the pan. I'm gonna put it back together tonight with lucas oil and a new filter just to get it out of the shop for the weekend and hopefully I can get a PCS by saturday. Is there anything else I should try?