My truck is psychic

[LagunaH1]

I SWEAR it must have read my mind that there's a bit of money coming in at the end of January because the truck decided to act up today:


I was driving down the freeway on cruise control at about 60 Mph when it suddenly felt like the truck "stepped on the gas" and started pulling. I immediately canceled cruise control and everything seemed normal. I went back on cruise and everything was normal for almost all of the trip home. As I got to my freeway exit, I let off the gas, coasted to about 50 mph and then shifted from the normal "D" (overdrive) to no overdrive (3rd) and engine braked down to about 30 Mph and then shifted to 2nd. At that point I could feel the transmission trying to go to 2nd but it didn't really engage, it was like the truck was stuttering. this lasted for about 5 - 7 seconds until I had was at the end of the of-ramp.


About 1 minute later I was going up-hill and was on the gas pretty good. I'm not sure what gear I was in, but the shifter was in the normal "D" (overdrive) position. The truck started bucking hard, and the revs were going up and down along with the bucking. It was like it was hunting for gears or the torque converted was locking / unlocking over and over.


I know there's been threads about what may cause the TC to not lock correctly so I guess I'll be doing some research online tonight. I should probably also scan for codes.


Anyways: It's just kinda ironic that it happens right now when it looks like the financial situation was about to get better.

 

[06 H3]

Sorry to hear the crappy news. Hopefully it works itself out

 

[3Hummers]

They feel the extra weight in your wallet and want their share.

 

[Mb30sdl]

Fuel filter?

 

[Pappibri]

Sorry too hear, hope that its something minor

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[LagunaH1]

I'm going to start by looking at the speed sensor in the T-case.

 

[3Hummers]

Good first guess. Also easy and quick. It is a one minute check.

 

[SuperBuickGuy]

psychic? I'd vote for evil - good trucks make sure the right webpage is open for a good modification (ARB lockers, etc). Evil trucks want stupid parts (emission controls, etc)

 

[LagunaH1]

So, I pulled the vehicle speed sensor from the T-case today and it looked really quite good and clean with only a tiny amount of dirt near the thread. A quick wipe and I re-installed it.



As I was poking around under the truck, I noticed that the T-case lock switch plug only has 1 wire attached to it:


Is that normal? The service manual drawings look like there are 2 wires going to that plug

 

[LagunaH1]

Update:


I decided to see if I could reproduce the issue tonight. I got in the truck and drive around the block twice, which is probably a total of 4 miles.


Shifts from 2nd to 3rd are very firm, which they didn't use to be


I had been doing some searching & reading here and found mentions of the TPS being the cause of some shift issues.


After the roughly 4 miles, I pulled in to a gas station to check the fluid level in the transmission assuming that the transmission would be warm enough to yield a reliable reading.


I was pretty shocked to see that there was NO fluid on the dip stick. I put in about 1.5 quarts of ATF and limped home


SO: I'm now obviously thinking that the issues I had this past weekend were due to low ATF levels. I don't quite get it though: I checked the fluid levels before heading out on my roughly 80 mile drive this past weekend and there was plenty of fluid in the transmission so it must have gone somewhere and the truck isn't leaking.


Next, I'll check the fluid level in the T-case, just in case I have yet another vampire

 

[SuperBuickGuy]

the TPS will throw a code if it's wrong. GM has 2 sensors on the throttle body that must agree, and 2 sensors on the pedal that must agree - if any of those are in disagreement; you'll get a code.

fluid will do all of those things (lack of)

 

[3Hummers]

Check T case fluid levels. Have you checked your air filter housing for fluid? Might look at geared hub fluid also.

 

[LagunaH1]

I'm running with the vent hose disconnected from the air filter housing for this very reason and there's no signs of ATF there. I'll get under the truck tonight and open the fill plug in the T case and see what happens. If that shows an overfilled T-case then I'll move on to the hubs and check for signs of ATF there

 

[LagunaH1]

Had a good chat with Mike today. There are several things other than a dead / damaged transmission / low fluid that could cause the symptoms I'm getting. Truck is headed to the Hummer Day Spa soon

And I DEFINITELY didn't drool on any of the Alpha's in the showroom....

 

[3Hummers]

Liar.

 

[LagunaH1]

I'm going to start by looking at the speed sensor in the T-case.

Update: I'm told that the "bucking" / hunting for gears actually WAS the speed sensor after all. It apparently would short out when the T case (and thus the sensor) got warm. So far, good news from Mike @ Tustin Hummer

 

[Bigunit]

Great news!

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[3Hummers]

Relatively cheap fix. Good news.

 

[alrock]

Great, more time to fix up Daisy's home in the back seat.