Strange transmission Problem??

Anyone have any ideas what this might be? 1998 s10 4.3 automatic. Driving at about 60mph if I have trans in 3rd gear It feels kinda like the trans is slipping. Basically a series of slight bumps and pulses. When I put it back in Drive I don't feel anything abnormal, and all other types of driving seem normal. Trans fluid is good, and at right level. Any suggestions would be appreciated.
Thanks

Fluid level and condition?
Has it ever had a filter service?
Any transnmission or engine codes?

Filter and fluid change. ( only what was in the pan. Not a complete change) about 35,000 miles ago.
Fluid appears to be in good shape. At least its still red.
Trans does have 185,000 miles on it however, so this is not really unexpected.

Oh. as far as codes go , nothing has tripped the service light, but that doesn't mean there is no code registered

Get it on a good transmission and engine capable scanner.
And check for codes and operation.
Also remember the engine has to be running up to pat for the transmission to work right.
If any codes past present or history post back code no.
Good luck MT

Get it on a good transmission and engine capable scanner.
And check for codes and operation.
Also remember the engine has to be running up to pat for the transmission to work right.
If any codes past present or history post back code no.
Good luck MTApologies for jumping in on this thread but I'm new & can't start a new one yet. Probably have to be approved. Great site ya'll have here but there's no forum for IH:disappoin :2cents: I have a code 37 when I jump the ALDL of a '94 S-15 Jimmy 4.3 120k mi. auto trans. My manual states it's an internal transmission problem & should be taken to a dealer or transmission shop. My friend just bought this Jimmy. It has the leaking fuel line in the intake so I told him we should make sure the trans is not getting ready to flop before spending the dough on the fuel injector kit. Is $285 a good deal for a complete replacement kit [injector,poppets,& nut kit suposedly. Haven't seen the pic yet] or is there a better deal out there? One more thing would you know the labor flag for the fuel injector job? Thank-you for ya'lls time.

Apologies for jumping in on this thread but I'm new & can't start a new one yet. Probably have to be approved. Great site ya'll have here but there's no forum for IH:disappoin :2cents: I have a code 37 when I jump the ALDL of a '94 S-15 Jimmy 4.3 120k mi. auto trans. My manual states it's an internal transmission problem & should be taken to a dealer or transmission shop. My friend just bought this Jimmy. It has the leaking fuel line in the intake so I told him we should make sure the trans is not getting ready to flop before spending the dough on the fuel injector kit. Is $285 a good deal for a complete replacement kit [injector,poppets,& nut kit suposedly. Haven't seen the pic yet] or is there a better deal out there? One more thing would you know the labor flag for the fuel injector job? Thank-you for ya'lls time.


Welcome to AF

If you can get on the AF forum You should be able to start a new thread.
Go to the GMC Jimmy forum and look for the New Thread button upper right corner.
For more help start a new thread/post.
Code 37 is only a TCC lockup clutch brake switch problem.
Start with clearing the code and see if it comes back.
A miss adjusted TCC brake switch or riding the brake pedal with you foot can set the code.
Does the lockup work and go off when youpush the brake pedal a little?