Transmission default.no shift. Now RPM. gauge not working.1996 k2500 4x4.

[ronrymanr]

Auto Transmission not shifting. I would unhook the battery and it would shift again. After a period of time the RPM gage would not work. I could still reset by unhooking battery cable. Now its random? that is it will not reset always. In the past I replaced the shift selinoids. still no improvement. Checked fuses crank position. trans. Does step motor on rpm gauge prevent shifting? when no shift condition speedo. rpm i think other gages do not work until reset occurs. where do I check next. This is a retired plow truck. with Alison transmission. looks like aftermarket ignition. the plow lights were grounded to the abs wheel sensor ground. that fixed by me years ago. this problem has been put up with far too long. but now the reset dosent. correct the problem any longer. so I need to fix it. I don't have the $ to pay a shop to fix it. Please respond. thank you.[emoji223]

 

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[Jsdirt]

On a plow truck, I'd be checking powers and grounds to the transmission control module, and any and all connections related to that. In fact I'd be checking ALL ground points on that vehicle, and getting out the wire wheel to clean everything up. Might even have to cut some of the wires off and put new connections on if they're corroded real bad.

 

If you live anywhere in the salt belt, these are the first things I'd check.

[ronrymanr]

Yes that was what the pickup was used for originally.The first 80 thousand miles. The Transmission is in great shape and the grounds are fine. when the rpm gage wont function as well as the speedo. I was able to reset whatever is causing this default transmission problem by disconnecting DC. power. There was a recall on these trucks I have read related to the stepper motors on the speedo/info board. I would like to hear from someone who has worked through this problem . I need to know how the crank position sensor and coil relate to shifting the transmission? Or what exactly happens or controls shifting of gears. What systems are at work before and after the shift selinoids? Im a member of the seadoo SBT tapatalk. Im wondering if that same increadable insight is here as well. What might be causing the failure?

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[ronrymanr]

Where would the transmission control module be at? Do you mean the vtm. or crank position sensor? the ECM was replaced with exact part #.

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[Hillwood]

Auto Transmission not shifting. I would unhook the battery and it would shift again. After a period of time the RPM gage would not work. I could still reset by unhooking battery cable. Now its random? that is it will not reset always. In the past I replaced the shift selinoids. still no improvement. Checked fuses crank position. trans. Does step motor on rpm gauge prevent shifting? when no shift condition speedo. rpm i think other gages do not work until reset occurs. where do I check next. This is a retired plow truck. with Alison transmission. looks like aftermarket ignition. the plow lights were grounded to the abs wheel sensor ground. that fixed by me years ago. this problem has been put up with far too long. but now the reset dosent. correct the problem any longer. so I need to fix it. I don't have the $ to pay a shop to fix it. Please respond. thank you.[emoji223]
 
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1996 with an Alison? What engine do you have?

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[ronrymanr]

The 350 5.7L. automatic

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[Jsdirt]

A crank sensor has nothing to do with the transmission whatsoever. The crank sensor tells the ECM (engine computer) where the crankshaft is, in order for the ECU to deliver fuel and spark at the correct time. Without it, you have a no-start condition.

 

How do you know the grounds are good? Did you voltage drop test each one of them?

 

How did you get an Allison mated to a 350? More importantly, WHY?

[carkhz316]

21 hours ago, ronrymanr said:

 

Auto Transmission not shifting. I would unhook the battery and it would shift again. After a period of time the RPM gage would not work. I could still reset by unhooking battery cable. Now its random? that is it will not reset always. In the past I replaced the shift selinoids. still no improvement. Checked fuses crank position. trans. Does step motor on rpm gauge prevent shifting? when no shift condition speedo. rpm i think other gages do not work until reset occurs. where do I check next. This is a retired plow truck. with Alison transmission. looks like aftermarket ignition. the plow lights were grounded to the abs wheel sensor ground. that fixed by me years ago. this problem has been put up with far too long. but now the reset dosent. correct the problem any longer. so I need to fix it. I don't have the $ to pay a shop to fix it. Please respond. thank you.

 

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Your title says '96; profile says '95. In either case, I'm going to assume you have the 4L80e trans. I'm not sure what you mean by aftermarket ignition, but this is disconcerting. The erratic shift/ no shift scenario indicates to me the trans is likely going into a limp mode, no doubt due to loss of power to the trans via the ignition. During this "no shift" time, does the truck lug from a stop like its taking off in a high gear? (4L80 limp mode defaults to 2nd gear).

[ronrymanr]

Yes it lunges as I put in reverse or forward. In the past I was able to reset by restarting. There after by unhooking battery cable. I FINALLY MADE THE CONNECTION WITH GAGES NOT WORKING. the ignition was on the pickup when purchased. It has a long key maybe original had a chip. see pic. Its a 95 sorry. Is the ignition hard to change? Are the contacts. in ignition going bad or is it the wireing that fails? So there wouldn't be a no start condition if ignition switch is getting worse? will there be a code for failed ignition switch? Do you know if there are other conditions (failures) that cause the limp mode? thank you.

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[ronrymanr]

I SAID AFTERMARKET. I MEANT NOT ORIGINAL.

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[Jsdirt]

Where I come from aftermarket = not original ...

 

If the original had a chip, you wouldn't be getting the truck started. That's for vehicle security only, and effects fuel delivery (shuts injectors down). The security light would blink while cranking, the truck would start and run for 2 seconds, then die.

 

Check powers and grounds, and the connector down at the transmission like I mentioned earlier, and let us know what you find.

[riverbanks]

Do a search for vss buffer problems

[ronrymanr]

It looks like the steering lock was taken out . the plastic cover is not there any longer . I haven't done it but im pretty sure I could pull the key out while its running. I will check grounds and trans connection and wires. other fuses too. It must be intermittent to be able to reset or works then not work. crazy . Thank you for your patience and advice[emoji173]

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[ronrymanr]

What does vss stand for.?? sorry im just seeing your reply. Im working on a Durango that has rear wheel abs . and learned about an ABS SPEED SENSOR on the differential. I have no voltage at the fuse for this. Im wondering if a speed sensor on my k2500 may have a short to ground???? Anyway thank you for helping !!!

Do a search for vss buffer problems

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[Jsdirt]

VSS - Vehicle Speed Sensor.