GMC Jimmy Tranny Problem?

[nthomps66]

Can the transmission on my 2000 Jimmy can overheat and shut itself down somehow?

I was pulling my boat last night on 35W. I thought something was wrong because I couldn’t get it up to the speed limit (70mph) which normally isn’t a problem. I turned off the A/C and that did nothing. Then it just started losing speed and finally It wouldn’t go over 30 mph. The engine would rev high RPMs but not go any faster. I thought for sure the tranny was slipping. I unhooked the boat and had a friend take it home for me. I then tried the Jimmy again and it worked fine. I drove it home with no problems.

I drove it to work today too. I don’t know what to do. I might hook the boat back up tonight and see what happens.

I was using the “Tow/Haul” button like usual. The truck's manual says I can pull 4500 lbs. My boat/motor/trailer weighs less than 2800 lbs I believe.

Is it worth fixing or should I trade her in ASAP?

[jimh874]

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I've got a similar Jimmy (1996, 4.3 liter) I'm noticing when I have cruise set (say 60 mph) and if I got up a slight incline of a hill, I can feel a lurch or a slip or a lug...tough to explain. It's silent, but I can feel it. If I put more gas pedal down, she switches gears and it's fine. Seems like it only happens when it is just about to switch gears, but I have to help it by giving it the gas. Any thoughts on my Jimmy tranny?

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Anyone? Anyone?

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it might be right in the sweet spot where its hunting for a gear to be in. the converter wants to lock, but unlocks thinking its going back down a gear, thats what your surge is.

tell ya what, send me your addy at jim874 at earthlink dot net, title it "fm member" and i'll send you the same sight i sent nthomps66. its one of the more well known s-10 sights on the web, lots of information there to be had.

jim

[Macgyver55]

Ooops. I replied earlier but must have forgot to hit submit. Anyway, it's normal for the converter to come out of lock up before down shifting, but not to do it multiple times. Usually its a smooth transition that you may or may not feel, but if it is dropping in and out multiple times I think you would easily feel it. True tapping the brake will unlock the converter momentarily, but if it is not receiving the proper throttle position and vehicle speed sensor signals it will try to relock. It could be something as simple as a misadjusted throttle position sensor or one that is going bad. I've seen them go bad on high mile vehicles where the driver uses cruise control a lot at the same speed all the time. It can cause a wear spot in just one particular place in the sensor but still operate fine at other speeds. A simple "sweep test" with a scan tool will usually catch it if this is the problem. A bad VSS (vehicle speed sensor) can also cause the transmission to act erratically. A test drive with a scan tool connected will show if the transmission is getting a good constant signal from the trans. Transmission problems are difficult to diagnose without driving the vehicle, but many times are caused by other related factors. You have to make sure everything is running right before a final determination can be made.

[Hemlock]

Thanks guys, I will take your ideas to a mechanic friend of mine and see if we can put it to a test to determine the problem.

[Jeremy airjer W]

Yes it does Dan. Most if not all vehicles with OD will do this. Try it sometime. Hold a steady throttle on a flat grade at cruising speed. Apply light pressure to the brake pedal. You should see and/or hear the engine rpm's increase. This test is one of "Paul Brans', from autotalk" favorites.

Macgyver55, Shame on you for doing a sweep test with a scan tool. Yes you may get lucky a few times but a good multimeter or lab scope is the way to go. Just had one last night on a Dakota. As soon as you breathed on the gas pedal it would go crazy. Suspected the TPS as the customer had already replaced plugs, wires, cap, and rotor. The scan tool was not fast enough to pick up the spike off idle, but the Mentor lab scope saw it everytime and the multimeter would show it on the bar graph but was still a little slow on the readout. To tell you the truth I don't think I've ever caught one using the scan tool.

[nthomps66]

Preliminary report says my Jimmy needs a new air flow sensor. They are doing a couple more tests though. He told me $380 for the air flow sensor. How should I feel about that?

[Dan Thiem]

GM part # 25180303 sugg retail is $216.00 with a discount it whsles for around $140.00. That's what I came up with for a 2000 Jimmy 4.3W. $380.00 seems a bit steep. Maybe it's more labor intense than I thought.

[Jeremy airjer W]

Mass Air Flow sensor or MAF. Two hose clamps and a four wire connector. Should take about 2 1/2 minutes to replace . I used to see alot of these and the GM's back in the late 90's hardly ever see them on the new stuff. Never replaced one on a blazer this new.

nthomps66, Make sure they have duplicated the symptom and are not just firing parts at it!

[Dan Thiem]

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Make sure they have duplicated the symptom and are not just firing parts at it!

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So true Airjer! There is a lot of parts replacers out there calling themselves mechanics. Not very many good drivability and diagnostic techs left out there. Now a days people just start putting on parts untill they get it fixed.

[Macgyver55]

Airjer, maybe I am just "lucky" but I have a Vertronics Mastertech and so far it has been flawless at finding even the most tricky TPS problems. It has a built-in automotive oscilloscope and a built-in digital meter. You can do voltage and current waveform displays and more. I've been around the block a few times, but I'm not saying I never get "fooled". Every one of us has been there.

I have a good old stand alone multimeter too just in case.

I just seem to use it less and less unless there is some question to be verified.

[Jeremy airjer W]

You must be a dealer tech? Lucky!!! There are a few of us that drool over Equipment like the Mastertech & DRB's. To much money for this guy to spend. I've never had any luck with the MT 2500 finding gliches. I recently purchased a Mentor/Genisys and the refresh is still slow but I did get the multimeter/labscope upgrade which makes it convienient. Everything I need in one tool!

Lets see Spend $4,000.00 to figure out that a $50.00 part is bad. Isn't autorepair great!

[Macgyver55]

No dealer job for me...they gotta work too hard for their money.

[nthomps66]

The symptoms were totally gone when I picked it up yesterday. $370 was the total bill for the sensor. Of all the people I got input from, nobody correctly guessed what it was. That means one of two things. Either I am bad at describing the problem or its too hard to diagnose car problems on a messageboard. Probably a little of each...

I drove it exactly one block to New Brighton Ford and traded it in for the big, bad, blue F150 Crewcab I am driving today! It matches the Crestliner and everything. Yesterday could not have turned out any better. The Jimmy was not too bad to fix. I got what I wanted for it. I got a lower interest rate then I expected. I financed less than I thought I would. And I took it home last night. My first new truck ever...pretty exciting.

[Macgyver55]

I am happy and sad at the same time. Happy you got the new truck, (new trucks are always GOOD) but kinda bummed that we will never know if the problem was fixed or not. I'm a "follow up" kinda guy so I'm always interested in outcomes of problems. You had already said that you "tried the Jimmy again and it worked fine (after unhooking the boat) and then "drove it home with no problems." No mention of any problem after that. Driving it exactly one block and trading it in isn't much of a test as to whether it was fixed or not. At any rate, you got your new truck. Somehow I think that outcome was in the cards either way by the sounds of it.

You're right though, it's very tough to diagnose car problems on a message board. It's kinda like calling the doctor and telling him about an ache or pain that comes and goes and having him diagnose it and prescribe a cure over the phone.

I do agree with Airjer, we used to see these fairly often back in the mid to late 90's and hardly ever see them on the new stuff anymore. Haven't replaced one yet on basically anything this new.

Good luck with the new truck, I hope you enjoy it!