I have a 1994 s15 jimmy with the 4.3L vortec cpi and automatic transmission. After driving for a few minutes and the transmission begins to warm up, i have to really strain the engine to accelerate and run at 4,000 rpm's to keep up at highway speeds. And i've also noticed it takes a couple seconds longer than it should for the transmission to engage from park to drive. Also when i come to a stop, engine starts to over heat and wants to die. Any suggestions? I was thinking the torque converter may have went bad, but i was told it could be a solonoid of some sort as well, or it is my worst fear that the transmission is trying to lock up because it sat for 3 years without moving. What do i need to check to diagnose this issue?

 

Would a bad torque converter cause this or would it be something else?

 

Checked the fluid? if so what was the condition of it?

 

Fluid is brown, but it was like that before the tyranny started acting up, plus with 180,000 i'm scared to do a flush, would a drop and drain be sufficient enough do u think?

 

Ehh.. I don't know, depends if it was changed some throughout its life or not. If not, sometimes the old fluid is whats holding it together at that point. Most of your transmission shops should give it a test drive for free if you want to try that out. Because 4K rpm on the highway is way to much! My blazer does right around 2K at 65-70mph if that tells you anything.

Here are a few questions:

Assuming it isn't throwing a code?

Does it seem to be shifting gears ok? (smooth and such while driving)

Is it making it to the higher gear, at the higher speeds? (55-65mph)
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Play with the overdrive switch, (if equipped) and make sure your shift indicator hasen't moved over a notch. (P_RND21) You may be riding around in second/third. I'm not sure about your interior setup. If its a digital shift indicator then it's more unlikely that would happen, certianly wouldnt hurt to try if you havent already..

The engine overheating is probably something unrelated to the tranny/rpm issue, as far as that goes you may want to have your water pump checked. I would think that if it were the thermostat it would overheat and stay that way. How hot is it getting? If your guage has actual numbers on it, I wouldn't let it go over about 220 deg.

 

No codes, digital gauges, and it does shift into overdrive, it just wont maintain a steady speed, it gradually decelerates until it kicks down a gear. But it shifts fairly smoothly, and I just put a new waterpump and thermostat in as well. As for the temp, it never runs in the red just above 210° , and it only overheats when i'm at a stoplight or stopped when driving. Then it overheats and wants to die. But if I let the engine run in park from cold before driving, it runs good an doesn't overheat, it can idle for 2 hours and not overheat, it only does it after I start driving

 

Is trans fluid level rising?
When you pull into driveway, pop hood and check trans cooling lines into rad tank. Bet they are hotter'n blazes. If so, Your trans is eating itself up with slippage.
Run, dont walk, right now and get some Lucas AT fix and put it all in. Better yet get another for later because you cant wait until you do the following...

I wouldnt do a flush either. But brown trans fluid points to possible problems with coolant into trans due to bad radiator trans cooling lines. You need to disconnect the trans line at rad tank and do pressure test. Or simple disconnect while engine stopped still hot and pressure on radiator. If no pressure or coolant running out there then probably okay.

I would drop trans pan and check for water / coolant also.

Dont disturb filter other than wipe and clean lightly IF you dont find coolant. Then pour in a{nother} full bottle of Lucas AT fix. Worked for me for addl 130 kmiles but yours is further gone than mine was. Top off with generic GM type AT fluid.

BTW, the Lucas doesnt work immediately but in a few hundred miles should be good if it's ever going to be.

Adding more trans fluid cooling {tranny cooler} wont hurt either and it's relatively cheap.. compared to rebuilt trans.

 

What he said

 

Ok, ill test the transmission fluid lines to the radiation for pressure and coolant, and do a drop and drain and check for water in trans pan. May be a while before I can post results as I'm out of the house 16 hrs a day working... still open for other suggestions to help diagnose this issue. Thanks guys

 

Look... diagnosis can wait unless you're in a hurry to make a different decision.

Get that Lucas AT fix in there before it doesnt have anything to work with.
Your trans is toast by any shop definition.. the Lucas sure aint gonna hurt.