Transmission issues

[yuflesh]

Hey guys, I was hoping you can help. Tranny does some weird stuff. Right around 60km/h (35mph) between second and third, if you are on a straight stretch and barely any gas applies, it will jump between second and third. Back and fourth, really annoying. No load, just the truck. Its a 1992 GMC 3/4 ton with about 40,000 miles on the tranny. Does the same thing between 3rd and 4th at about 90km/h (50mph)

Im thinking (and Im not an expert on trannys by any stretch of imagination) it could be the kickdown cable, (or does this thing has tv cable). One thing that I did notice is that tranny fluid is slightly overfilled, and there are some bubbles on the top. I was thinking about dropping the pan this weekend, changing the fluid and filter, but Ill wait for your opinion first. Oh yes, fluid is nice and red, and it does not smell burnt at all.

Can anyone help out?

Thank you very much

Marko

[john8662]

Probably have to ID the transmission.

Do you know what transmission came in the truck?

For '92 you have two options, the 4L60E and the 4L80E. The 4L60E is more similar to the TH700 and will be found in 1500 series and light duty (6 lug wheel) 2500 series. For 8 lug 2500 and 3500 series, you'll likely have the 4L80E.

For either one, you're most likely to not have a TV (kickdown/detent cable) as it will be controlled mainly on speed sensor in the tranny and the TPS on the injection pump.

I suspect at this point that it's the TPS sensor on the injection pump that is failing.

As for the tranny fluid being slighlt overfilled, don't sweat it, that's about the normal, and actually the way I always fill a tranny, because they're picky about being just slightly too low...

[yuflesh]

thank you for the response. Just to clarify, chassis is K2500, engine code is C. It a 2500 with 6 lugs. I will look into how much is tps sensor, and maybe if its cheap I will replace it. Is it a pain to replace? I thought it was 700R4, but then again I bought this truck 6 months ago, and coming from world of Diesel VW's this is all new to me.

I also lied, truck is actually 1991, NOT 1992, it is manufactured in 91 and registered in 92. Im not sure if that makes any difference. Its newer style (2 bulbs per side - one light) not two lights like the older trucks)


Ive also found out tonight that my "CHECK ENGINE" light does not come on when I turn the key over. I tried to see if I have any codes, but the light is dead (or someone before me pulled it out)

This would sorta explain rough idle Ive had since I purchased the truck. I was told it has a rough idle because muffler pipes are pretty much straight dual pipe, so they are more open. Smell like bull.... to me.....


Ill open the dash tommorow and take a boo.


Thank you again for your help.

Marko

[john8662]

What's the build month?

1992 was the first year for the 4L60E tranny, so that's why the commotion.

Look behind your aircleaner on the driver's side rear for the TV cable, if you've got a cable that runs down to the transmission, then it's a 700R4.

If it's 700 with the flare, something come to mind, maybe it's not shifting from gear to gear, but what you're feeling is the torque converter locking and unlocking. This would point towards the TPS as well.

As for the idle, the open exhaust won't have anything to do with that, but it will shake more in the cab if the exhaust is touching something, etc.

Wish you well!

Oh yeah, welcome to the page!!!

[yuflesh]

What's the build month?

1992 was the first year for the 4L60E tranny, so that's why the commotion.

Look behind your aircleaner on the driver's side rear for the TV cable, if you've got a cable that runs down to the transmission, then it's a 700R4.

If it's 700 with the flare, something come to mind, maybe it's not shifting from gear to gear, but what you're feeling is the torque converter locking and unlocking. This would point towards the TPS as well.

As for the idle, the open exhaust won't have anything to do with that, but it will shake more in the cab if the exhaust is touching something, etc.

Wish you well!

Oh yeah, welcome to the page!!!

build month is 01/91. Apparently was not sold till 92.

Anyhow, got the bulb replaced for check engine light, and yes it was burnt out.

Two codes came up. 33 and 21. (and of course 12 - diagnostic but that does not count)

One is TPS, as you suggested, good call. The other one is MAP sensor, I think. Is map sensor sitting on the firewall, driver side. That is the only thing that is similar to map sensor. But Im not sure. I know where TPS sensor is.

Now, do you guys have some wicked sources for parts. Im in Canada, but dont mind buying from the states. I was quoted 280 dollars for TPS sensor (about 250 US dollars) and I just about got a heart attack. A bit pricey. Didn't even dare to ask about map sensor.

If someone has some sources, please hook me up, or Ill go to the wreckers.

How do you tell (at the wreckers) if the TPS sensor (or map sensor is good) Just need to know testing procedure.

Thank you for your help.

Thank you for warm welcome too, its been a pleasure so far :D

Marko