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1997 P30 Gm Stepvan not shifting out of 2nd gear

Alia Beydoun

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Brooklyn New York
Hi,
I have a 1997 Chevy p30 stepvan. Hoping someone can help. Truck was driving fine till I brought it in a shop for an engine oil change and a brake adjustment. I pull out of the shop and truck wouldn’t come out of first gear. Park, reverse and drive is fine, no jerk at all. Fluid clean. Truck drives and revs not going out of first gear. Brought it in to a few trans shops and all are saying needs a rebuild trany without looking and checking it.. any help would be appreciated!
 
Limp mode is when the transmission won’t shift like yours is doing to protect itself from more damage and to help you make it home in a pinch.

I think there are a couple different reasons for the transmission to go into limp mode. Like said above, You need to get a scanner on it to have some sort of idea of which way to go.

If it was running fine when you brought it to the oil change station then I don’t see why you would need a rebuild all of a sudden.

I’m betting that they have done something to the transmission wiring harness while they were under there.

@THEFERMANATOR
 
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I believe there is a sensor built onto the shifter on the transmission, crawl under and be sure the harness is plugged into it.
 
Thanks,
So I went to a shop today and they believed the truck was in limp mode as you guys said. They also think it’s a glitch and unplugged the battery for 20 min to reset the computer. They tested some sensors and found no problem with wires or sensors. Truck now shifts out of gear and drives normal. I feel like this problem will come back. Any thoughts? Does this sound about right?
 
I’m just guessing here but, you might have a nick somewhere in the harness and it’s grounding out. They got up under there and moved stuff around and “ungrounded” the wires.

If it ever happens again. Shut it off. Climb under it and try moving the wiring harness around and then start it up and see if it fixed the problem.
 
Hi,
Thank you for replying. There is no check engine light coming on.

To be blunt so it makes sense: Service ENGINE Soon is NOT Service Transmission Soon! The "It's going to cost GM warranty money SES light" only comes on because the EPA is holding a gun to GM's head. The light is nearly for emissions failures only.

@MrMarty51 is correct in suggesting getting a code reader on it. 'Disconnected the batteries' should not clear the code from memory. Older stuff it can clear codes completely and I am fuzzy if it would for your year. (Battery disconnect can reset the limp mode, but, this is generally done by normal key off key on. @Jaryd eludes to key off key on reset. The ECM checks for the condition after key on and only limps again if the condition still exists. ) The correct way to reset a limp mode is with a scanner - the battery disconnect is an outdated hack to get you down the road hoping it's intermittent without fixing it. Stop by an auto parts store and have them scan for codes. Did the shop tell you what codes were in the computer? Again this code is just for future reference if the problem comes back. The shop may have fixed the problem, like pinched wires, w/o telling you.

Again it limped so it will have a code as to why it limped.

What's the trans oil look like? Level?

What items do you move to change the oil? Look around the oil filter for damaged wires. Doghouse pinching wires?
 
Something I did once was trans filter change and pinched the wire inside the trans with the pan. That one took a bit to realize. Everytime I started the truck it would drive theough all 4 gears. Then when slowing down it would default to 2nd gear only. It reset every time the key was cycled. Annoying. I had 3 different trans shops tell me “full rebuild”.

I only found it because he brand filter I used, I heard had some tearing problems. (Wasn’t my issue) So when I threw in a different filter, I saw the wire. Figuring a rebuild was needed, I just left the flattened wire but not pinched this time. Over 30k miles later, all is good.
 
Hi , I have 1999 Chevy P30 5.7L 4 speed mini school bus which I am converting to motorhome, it’s not going in to fist gear right away only after reverse ,2 and 3rd gear slipping as well , I changed trans oil and added Lucas transmission gear fix fluid 2 bottles of 24 oz , it was working properly for few hours but went back to same , I think I may added too much Lucas trans fix fluid.Please advice any help would be highly appreciate. Thank you 🙏 in advance.
 
P30 chassis could come with a couple different transmissions.
Which do you have. If not sure take a couple pics showing pan and best passenger side pic as you can.
 
Hi Will, It’s 4l80e , called local oreilly store asking regarding transmission shift solenoid replacement part and I provided them with vin number and they told me part is for 4l80e transmission I can assume it’s 99% correct but I will take pictures of the pan and side of the transmission and will post later on today.
Thank you 🙏
Ivan.
 
Ok first, know that the 4l80e is an amazing transmission so if you end up worst case scenario a complete new one- you’re good for the next quarter million miles.

You need to get a scanner And pressure gauge on it. If you don’t have them, ya might do best stopping by a transmission shop for estimate, many will do it free and this trans is really well known.

There are several guys here way better than me on trans so wait for their response even if it takes a day, they might have something for ya.
 
The oil level is a real PIA to check esp. after sitting a long time. The converter drains back into the pan over this long sit. Then you take a real bath changing the oil. Next the converter just "foams" and it takes several tries to add enough damn oil. It looks good on the stick running warm, then after going around the block it's down over a quart literally sucking air and won't grab any gear. A trans I had sitting around and tossed in the truck did this to me. It took 6+ tries before the level was correct.

Again I am saying you may be low on trans fluid by 2-6 quarts. Esp. if you changed the oil like I did before firing it up after sitting 6 months.

Lucas transmission gear fix fluid ... You can really screw up a transmission shifting by adding different oils or "fix it" in a bottle. Word: DON'T.

Further use the "old" Dextron III and avoid the water thin krap known as DEXRON-VI. Bluntly it's a little thinner oil buildup on the tailgate when that VI krap lets your transmission burn completely out from being too thin for even the new stuff it's supposed to be for. If the bottle has VI on it it doesn't belong in your 4L80E (or Allison trans).

It's possible a P30 could have an Allison?

Not saying it's weak by any means, but, trouble areas: The 4L80E should have oil changes at 25K miles to keep the abrasives from wearing out the TCC lockup solenoid. Further the weak point is the TCC clutch so an aftermarket torque converter with a triple disk can give you longer life. Don't try to compression brake with it as another weak point, small overrun clutch pack, in the trans burns up easy although it's hard to notice that rarely used clutch failure.
 
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