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]

im going to guess you have a auto, torque converter slipping? check your fluid level/color lately? good fluid should be a transparent red, burnt fluid will be a darker red. sounds like your overheating your tranny fluid.

complicated to explaine how a converter works, but if your tranny fluid is getting to hot the converter will slip. any lenghty period of time running or pulling with a overheated tranny will also kill the clutch packs, and your tranny in a hurry.

do you have a external tranny cooler? or the one thats in the radiator? an external unit does a much better job of keeping your tranny at a consistent cooler temp.

meybe its a sign to upgrade?

jim

[nthomps66]

So far I have two mechanics saying that the tranny is going bad- trade it in.

Another mechanic just said it may be the fuel pressure regulator.

I failed to mention that the truck was having other issues. Every time I start it it takes a minute or two to "warm up". If I hit the gas before it "warms up" it does nothing but bog down. It won't even move. Then it finally kicks in one cylinder at a time and goes like normal.

Could this have caused the problem while towing the boat last night? It was starved for fuel, therefore it slowed down. Intermittant spurts of fuel caused the revving?

I'd appreciate anyone's commentary and/or expert advice. A $500 fuel pressure regulator is much better than a new tranny!

[FullTilt]

One problem I had when towing with my Jimmy was the catalytic converter. As the mechanic explained it, the catalyic converter gutted itself and plugged the exhaust. I became a one vehicle parade limping down the shoulder of I35. The truck gradually lost power over the course of a couple hundred miles. Eventually it would barelly do 15 mph and I made it to an exit ramp. This happened at 35K on a truck I bought new. This truck did not like long pulls, especially in the heat. That was the second time in two weeks that truck left me stranded more than 150 miles from home. A week later I lost my shorts on the trade-in for a bigger vehicle.

[Hemlock]

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?

[nthomps66]

Full tilt- You are person #2 that suggested the catalytic converter now. This theory is gaining some steam.

Your symptoms were exactly the same as mine while towing the boat. I was a one man parade going 30 to the next exit with the flashers on too.

Did yours run OK after you released the trailer?

[blakjack23]

I had a 96 GMC Sonoma that was doing the same thing, though I wasn't towing a boat. It was the catalytic converter. Hopefully thats your issue, not to expensive to fix.

[nthomps66]

Jim- thanks for the input. I have no idea what a tranny cooler looks like or where it would be so I can't answer your question. Up until now I had no idea a tranny needed a cooler...

I will see if I can check the fluid tonight.

[Macgyver55]

Quote:

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Another mechanic just said it may be the fuel pressure regulator.

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With the "other" symtoms you added I'd tend to agree with this guy. When a bad regulator acts up it will indeed affect the transmission shift points/performance. They also seem to "act up" the most in hot conditions. In addition if you are having starting and performance problems to boot it's important to get those addressed first. Transmission problems cannot be properly diagnosed without the motor running correctly.

A converter is also a possiblity and can cause poor performance, but usually conditions don't improve when warmup is reached. I'd have fuel pressure checked first.

[Dan Thiem]

I just looked up a fuel pressure regulator and upper intake seal kit. GM's suggested retail for the regulator is $84.77 and the upper seal kit is $32.92.

Quote:

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A $500 fuel pressure regulator is much better than a new tranny!

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[Dan Thiem]

Also have the trouble codes that are stored in the computer pulled and see what you get.

[Macgyver55]

Quote:

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have the trouble codes that are stored in the computer pulled and see what you get.

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Good point....he didn't mention a check engine light so I neglected to say that. Most times regulators and converters won't set a code.

[FullTilt]

Regarding the catalytic converter problem, I didn't have a chance to try it without the boat or at a later date. I abandonded it at a gas station in Pine City and had someone come get me and the boat. I was surprised that this was the only problem considering how bad the truck ran. If you tried to push on the gas it would bog down terribly, I couldn't even go 30 mph. The fact that your vehicle drives fine after it's cooled down leads me to believe the catalytic converter isn't your primary problem.

[united jigsticker]

On a 2000, the fuel pressure regulator should set a code.

2 quick things on the catylitic converter:

#1, if they are plugged, the vehicle will typically smell of "rotten eggs" when driving.

#2, if the vehicle ran well after cooling down, this is not your problem,

Did you notice the vehicle shifting in and out of a lower gear before this happened?

Pull the tranny dipstick, give it a visual and a smell test. The fact that you were pulling RPM's still doesn't convince me that it's a fuel pressure regulator.

These 4.3 engines are not prime for towing, nor is the tranny anyways.

I'd trade it for a full size if it seems to be running OK now. Finding what the problem is and THEN trading can lead to CARFAX reports diminishing your trade value.

Besides, GM is offering employee discounts to the public right now!!!

[nthomps66]

I checked the tranny fluid and it is a transparent red. It didn't smell funny either. That's good news.

I have an appointment on Thursday morning to get it looked at. All of this speculation isn't getting me any closer to my new F150! All indications say its a fuel line problem at this point from what I hear. I just hope it's a cheap fix that gets me a decent trade in value. I will let you guys know what becomes of this as soon as I get the call Thursday.

[nthomps66]

UJ- It wasn't shifting in and out of a lower gear. It bogged all the way down to 30 mph with petal to the metal.

I think it was getting spurts of gas, revving itself up and putting itself into a lower gear making me think the tranny was slipping. Really it was gulping for gas. That's just my theory now that I've read all the posts and spoken to a couple mechanics. We'll see what happens I guess.

By the way- Ford is offering the same employee discount now. I've had two bad GM vehicles in a row. Time to switch squads!

[jimh874]

tranny cooler looks like a smaller air conditioner condensor that sits infront of your radiator. you most likely have the stock cooler and thats located in the radiator. i would post a link to a pic, but trouble would come because, well. i have one in my mustang and love it.

anyway.....

yes, definatly let us know. on the new computer controlled obd 2 systems, it takes a code reader to diagnose about 90 plus percent of the problems.

jim

[Macgyver55]

After rereading the thread I realized that we may have overlooked the obvious here. Before going too deep into this, has the fuel filter been replaced lately? A plugged filter will exhibit some of these same symptoms. Pulling a boat or trailer will exascerbate the symptoms because the vehicle needs more fuel when pulling. This possibly explains why it seems to run ok (or at least better) without the boat behind. A filter is cheap (around 10 bucks) and really isn't a waste of money, especially if it hasn't been replaced in the last 15000 miles or so. Besides, if you are going to check fuel pressure at some point, you should have a clean filter to get an accurate reading.

Make sure to let us know what you find when its fixed.

[raymondkr]

I have been also having problems with a GM 4.3 i would put money on your problem is the fuel regulator, One other thing does it start real hard right after it was shut. my left me sit 2 times. The way this fuel system works the regulator keeps the preasure at 50 psi and then it returns the rest of the fuel to the tank so if lets most of the fuel back to the tank the injector will not spray the fuel i have seen this happen on a dodge i had. sometime they act up only when it is real hot because they located on the intake manifold and they are covered by the runners you are looking at$65 foe regulator $30 gaskets and about 1 hour labor if you have the 4.3 vortek.

[Jeremy airjer W]

GM "vortec" engines require at minimun 55 psi to start. They will not start if the pressure is less than 55 psi. This is because of the "poppet" style injector they use. It requires higher psi to pop open.

[jimh874]

nthomps66

i would send a pm, but they dont seem to be operational, anyone know why?

well, i have a sight for you to visit, drop me a line at jim874 at earthlink dot net title it "fm member" i will give you a good forum to visit specificly for s-10's.

jim

[Hemlock]

Quote:

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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?

[Dan Thiem]

Hey Hemlock, I can't say for sure but it could as simple as the torque converter locking and unlocking. Does it do it while you are in overdrive?

[Macgyver55]

Are you sure you are not just feeling the converter coming out of "lock up". It will do this before down shifting.

[Hemlock]

I don't know what I'm feeling, that's why I'm asking!

It is happening while in overdrive, yes. Almost always, going up a hill, it happens 2-5 seconds before it would normall kick down a gear, or in some cases, I just put the pedal down a bit more and force it into the next gear. Should I not be doing this? At it's worst stage, it maybe lugs or lurches 3-6 times before I can't stand the feeling anymore and give it more gas.

[Dan Thiem]

A converter locking up is hardly noticeable. It's not like a gear shifting. Does your Jimmy have a tach? Try it in drive sometime not in overdrive. Or it could just be an engine miss. Does your SES light ever come on? Sometimes the E.G.R valve can get sticky from carbon and the aftermarket makes a gasket that has a screen in it. Another thing you should do is while it's happening tap your brakes and see if it does anything. I think that will automaticly unlock your converter. Won't it? Airjer? Mcguyver?

[jimh874]

Quote:

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Quote:

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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?