Transmission troubles

[DigitalBoy0101]

Left for work today and immediately as I left my driveway it was obvious my truck has troubles.

No first gear for sure, and I think OD is out as well. Service Engine light came on almost immediately, first time I've seen it in my truck. At 60MPH on the interstate I was turning 2400RPMs. I don't recall what normal RPM is at that speed, but I think that was 600RPM or so higher than normal. 3.73 gears and 265/70/17 tire.

I got a little whiff of transmission fluid when I got home tonight. Can't visually check my fluid yet because it's too dark, but it's time for a change no matter what.

Hooked up my Superchips handheld to read DTCs (hey, it IS good for something!) and what I got is:

P0758 Shift Solenoid B Electrical

Problem is, I have no idea what that means. Is that something internal to the transmission that I have to take it to a shop for, or something external that I can replace myself?

It may or may not mean anything pertaining to this problem, but I have a very occasional electrical gremlin. It happened for the first time about 10 months ago. Basically, my dash lights stay on but the gauge needles suddenly all go to zero for about 15 seconds. About 50% of the time the Security light would come on after that and stay lit until I got home. This happened once about every other day for around 2 weeks last winter, then it gradually went away over the course of another week. The truck seemed to still run fine, only the gauges seemed to have fits.

This hadn't happened again for about 9 months until I was driving home from work on Tuesday. No DTCs were ever shown.

The airbag idiot light has also been (mostly)on for about 2 months now, but again, no DTCs so I haven't really worried about it. Today was the first time my truck has ever thrown a code to my knowledge.

The only things I've done to my truck in the last year+ are new tires, a brake job and a new battery. I haven't even looked sideways at wiring of any kind.

So, what am I looking at here?

[RedHeartbeat]

Left for work today and immediately as I left my driveway it was obvious my truck has troubles.

No first gear for sure, and I think OD is out as well. Service Engine light came on almost immediately, first time I've seen it in my truck. At 60MPH on the interstate I was turning 2400RPMs. I don't recall what normal RPM is at that speed, but I think that was 600RPM or so higher than normal. 3.73 gears and 265/70/17 tire.

I got a little whiff of transmission fluid when I got home tonight. Can't visually check my fluid yet because it's too dark, but it's time for a change no matter what.

Hooked up my Superchips handheld to read DTCs (hey, it IS good for something!) and what I got is:

P0758 Shift Solenoid B Electrical

Problem is, I have no idea what that means. Is that something internal to the transmission that I have to take it to a shop for, or something external that I can replace myself?

It may or may not mean anything pertaining to this problem, but I have a very occasional electrical gremlin. It happened for the first time about 10 months ago. Basically, my dash lights stay on but the gauge needles suddenly all go to zero for about 15 seconds. About 50% of the time the Security light would come on after that and stay lit until I got home. This happened once about every other day for around 2 weeks last winter, then it gradually went away over the course of another week. The truck seemed to still run fine, only the gauges seemed to have fits.

This hadn't happened again for about 9 months until I was driving home from work on Tuesday. No DTCs were ever shown.

The airbag idiot light has also been (mostly)on for about 2 months now, but again, no DTCs so I haven't really worried about it. Today was the first time my truck has ever thrown a code to my knowledge.

The only things I've done to my truck in the last year+ are new tires, a brake job and a new battery. I haven't even looked sideways at wiring of any kind.

So, what am I looking at here?

Sounds like you might have a ground issue, a loose one or shorting out just behind the connector. Solenoid B, that would be the 2-3 shift noid at the back end of the valve body on the passenger side.

[GasGuzzler]

I'd say you have a fairly simple fix. No 1st or 4th? It has 2nd and 3rd right? I know that 3rd is off/off but don't remember off the top of my head the other SS combos. The encouraging thing is that you have an electrical code and not a mechanical or hydraulic code....meaning you can (without any other testing) blame the 2-3 SS, the single ground control wire for that SS from the PCM to the 20-way trans connector, or the PCM. That simple really. If you are cash strapped for diag money you could drop the pan and swap the 1-2 SS with the 2-3 and see if you gain the other two gears and lose the ones you had LOL. That code is pretty straight forward. If you have a loss of voltage to the trans connector (one wire provides power for the TCCS, both SS's, and PCS) you would have reverse and 3rd only.

[DigitalBoy0101]

Yeah, I'm pretty sure it has 2nd and 3rd gear. It bogs/slips like crazy from a stop, and finally starts to pick up speed decently at 20MPH. Before 20MPH it feels like I forgot to release the parking brake from hell LOL. I can feel one shift. Interstate RPM seems high, why I think I have 3rd and not OD.

I looked on O'Reillys, and it appears new solenoids are around 30 bucks each. That won't be an issue......cash is tight, but not that tight. My truck is paid off in 2 months and I'll have breathing room, so I can push the budget just a bit now and recover later.

Anything else I should do while I'm poking around in there? Replace other solenoids? I probably should replace the 1-2 as well just to be safe.

Since grounding might be an issue, how about this harness I found
Item Detail | O'Reilly Auto Parts

My fluid did get burnt a bit from driving it to and from work that day, around 20 miles round trip. Not horribly, but it's a bit dark and I can smell it slightly. I'll plan on refilling it with cheap fluid then driving to a shop to have the trans flushed. After the flush, I'll change the fluid again the next week on my days off with Royal Purple.

I'd rather not spend a lot of money on this trans, but it DOES have to remain reliable for another 3 years or so. Hopefully around that timeframe I'll be able to do an 80E swap, and then Allen's turbo kit.

Borrowed my dad's spare car again until I can work on my truck on my days off. Though it WILL drive, I'd much rather not risk further damage until I can repair it.

As always, thanks for the help!

[Vince_B]

A little info on a P0758. If the PCM detects a continuous open or short to ground in the shift solenoids or shift solenoid circuits the following occur. The PCM commands maximum line pressure. The PCM disables shift adapts. The PCM commands 2nd gear starts. The PCM illuminates the Malfunction Indicator Lamp (MIL).

With this being said you might not have a shift solenoid issue. It could be in the wiring of the vehicle. If you own a meter and know how to use it, I would start there first. You could OHM the shift solenoids and they should read between 20-40 ohms. If they show resistance then they are not open and should be ok. Then you are going to want to get a wiring diagram for your vehicle. You basically want to check between the main computer connector and the transmission main case connector. Resistance of wires should read very low. As I said before throwing parts at this issue check some stuff out. You might find that your issue is something as simples a loose or corroded connection. Maybe even a wire that has rubbed through and is shorted to ground. Vince B

[GasGuzzler]

Kinda what I said. Anyway...don't put crappy fluid in there just to get it flushed. If it's time to service it, replace the filter while you're in there and use a good quality fluid. Leave the flushes for when the trans is out and the cooler has debris in it from a failure. Flushes can cause more harm than good.

[Frenchy]

^True story, 3 flushes I've done resulted in dead transmissions, they were on there way out to begin with and the customer thought a flush would solve everything.

[DigitalBoy0101]

I suck with wiring, hate it with a passion >.< That being said, I guess it's time to buy a meter and see what I can find *sigh*.

If I can't find anything, which I think will be likely if it's not the solenoids, I'll have to take it to a shop and have them chase the electrical gremlin.

No flush then. Purpose of the flush was just going to be to make sure I got all the burnt fluid out. Guess I'll fill with Royal Purple, drive it a week, and change it with RP again.

Thanks all for the input!

[RedHeartbeat]

Change the fluid but don't touch the filter. You may want to do it twice to get the burned fluid out of the converter. Like I said before, don't remove the filter. When a trans gets old its used to a certain amount of flow and if all the sudden its starts seeing more pressures it often will blow seals and die a quick sudden death. You need the lubricity so freshen the fluid. I would stay away from the RP if it were me.

[Tank]

Take it to the nearest chevy dealer and have them replace the igniton/starter switch... fixed mine. Was doing th exact same thing. No first, a manual 2nd, 3rd default, and no OD. Shift pressures increased and no torque converter lock up. Said this a very common problem