Register or Log In To remove these advertisements. |
|
|
|
Thread Tools | Display Modes |
05-06-2016, 12:57 PM | #1 |
Registered User
Join Date: Mar 2014
Location: Redwood City
Posts: 242
|
4l80e not shifting, no speedo
Parked my 91 to swap the doors out for a power set and do a little work on the glow plug wiring. Everything went as I would expect but when I put the dash all back together and ran the truck it wont shift gears and my speedo stopped working. I changed the output speed sensor and there was no result. Before I throw anymore parts at it I'd like to just make sure I'm barking up the right tree. Can anyone give me a troubleshooting process to follow, to identify my problem? I'd really appreciate any help.
I also noticed that the wires from the output sensor had been repaired in the past near the trans, is there any reason not to re-run them from sensor all the way to pcm to just ensure they do what they're supposed to? Edit to add: the truck is an R model so it's a square body and has a square body gauge cluster if it matters.
__________________
1991 R3500 3+3 C+C 6.2/4l80e/14ff Fleetside Dually 1992 K2500 ECLB 5.7/4l80e/14sf(g80) 8600gvwr 1991 CR500 (95 Burb wouldn't stop catching fire ) |
05-07-2016, 11:07 AM | #2 |
Special Order
Join Date: Nov 2004
Location: Mt Airy, MD
Posts: 85,858
|
Re: 4l80e not shifting, no speedo
There are two speed sensors, one cheap and one expense. Could it be from the disconnect/connect taking the dash out? Is it well connected? I'd check into that first, if you haven't already. Yeah, you could run a wire end to end with soldered splices or just splice it there correctly.
__________________
"BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~ |
05-10-2016, 07:59 PM | #3 |
Registered User
Join Date: Mar 2014
Location: Redwood City
Posts: 242
|
Re: 4l80e not shifting, no speedo
swapped both sensors now and still nothing so I'm leaning heavily toward wiring issues. It's very unlikely I disturbed anything near the PCM when running the wires but it is entirely possible that I damaged the speedometer/gauge housing bc its a tight fit going in or out. Does the speedometer relay info to the transmission PCM or is the speedo info relayed from the PCM?
__________________
1991 R3500 3+3 C+C 6.2/4l80e/14ff Fleetside Dually 1992 K2500 ECLB 5.7/4l80e/14sf(g80) 8600gvwr 1991 CR500 (95 Burb wouldn't stop catching fire ) |
05-11-2016, 07:42 PM | #4 |
Special Order
Join Date: Nov 2004
Location: Mt Airy, MD
Posts: 85,858
|
Re: 4l80e not shifting, no speedo
I'm lost on that part. My next place to look would be at the connections, as well. Maybe if no one offers good info here you could try the Engine/Drivetrain section. Being not year-specific and full of techs you may have better luck there.
__________________
"BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~ |
05-11-2016, 08:44 PM | #5 |
Senior Member
Join Date: May 2009
Location: Fort Worth, TX
Posts: 6,370
|
Re: 4l80e not shifting, no speedo
The Speedometer, PCM, ABS, & Cruise get their VSS signals from the DRAC Module, The Output VSS is wired directly to the DRAC Module.
The DRAC basically converts the AC-Sine wave signal generated by the VSS, And converts it to a DC-Square wave signal that can be read by the above components. GM moved around the location of the DRAC a few times during Square Body production, If memory serves it's between the Steering Column & Ashtray under the dash, (The below location diagram agrees) BUT, Don't take this as gospel. Locate the Module & make sure its plugged in, The diagram shows a few inline connectors, So check those also. |
05-14-2016, 04:16 PM | #6 |
Registered User
Join Date: Mar 2014
Location: Redwood City
Posts: 242
|
Re: 4l80e not shifting, no speedo
When I did the door wiring I noticed the heater controls had a short on the wiring. To be safe i removed the fuse. GM in a fit of judgement of and wisdom decided to use the heater circuit to power the DRAC module. Unplugged the heater control and replaced the fuse, works perfect. Thanks guys.
__________________
1991 R3500 3+3 C+C 6.2/4l80e/14ff Fleetside Dually 1992 K2500 ECLB 5.7/4l80e/14sf(g80) 8600gvwr 1991 CR500 (95 Burb wouldn't stop catching fire ) |
05-14-2016, 06:55 PM | #7 |
Special Order
Join Date: Nov 2004
Location: Mt Airy, MD
Posts: 85,858
|
Re: 4l80e not shifting, no speedo
I learned something here. Glad you get her readin' and shiftin'.
__________________
"BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed" GMC '67 C1500 Wideside Super Custom SWB: 327/M22/3.42 posi.........."The '67" (project) GMC '72 K2500 Wideside Sierra Custom Camper: 350/TH350/4.10 Power-Lok..."The '72" (rolling) Tim "Don't call me a redneck. I'm a rough cut country gentleman" R.I.P. ~ East Side Low Life ~ El Jay ~ 72BLUZ ~ Fasteddie69 ~ Ron586 ~ 67ChevyRedneck ~ Grumpy Old Man ~ |
Bookmarks |
|
|