Jumping out of O/D

tmj_atx · 11-03-2009, 03:24 PM

Looking for a little guidance. A few weeks ago, my transmission began to hunt between 3rd and O/D. It got progressively worse over a couple weeks. This weekend, I started poking around and found the bolts on the TPS to be a little loose. Tightening those seems to have helped a bit. Now, it consistently shifts into O/D when it's supposed to, but if I'm doing anything over 40mph and ease up on the throttle (coasting, holding speed on flats, going downhill, etc, where I'm unloading the drivetrain) it drops down into 3rd. Apply throttle and it shifts back into O/D. I've started turning off O/D while driving around town at lower speeds to avoid the erratic shifting, but on the highway at 70mph, that's not really an option.

Thoughts? Given that tightening the TPS made a difference, think my problem is there? PCM?

__________________
1991 D250 CTD 2WD, pump turned up, stock everything else, 250k miles on the truck, 40k are mine

Philip · 11-03-2009, 10:07 PM

Here is how to adjust the TPS.

PDR Diesel Inc. The turbo diesel performance specialists! - 1st Gen TPS

__________________
93 W350 w/duals, fuel pin turned, 6X.018" injectors, 4" exhaust, 3" air intake horn, Super HX40/16, auto, 3:07's axles, 2" skyjacker lift, B&W flatbed

tmj_atx · 11-04-2009, 10:47 PM

Success! Checked the voltage and it cycled smoothly, but at rest it was jumping back and forth from 0.35V to 5V erratically. From what I gathered, it looks like when I tightened it back down the other day, it was just slightly rotated such that if you call rest position 0degrees, it was landing at negative 1 or 2 degrees, and hitting 5V. The tolerances of the screw holes on the TPS is just large enough to allow for this to happen. Loosening the TPS and rotating it just a hair in the opposite direction did the trick. Road test was smooth as butter.

Thanks for the info.

__________________
1991 D250 CTD 2WD, pump turned up, stock everything else, 250k miles on the truck, 40k are mine

Philip · 11-04-2009, 11:16 PM

__________________
93 W350 w/duals, fuel pin turned, 6X.018" injectors, 4" exhaust, 3" air intake horn, Super HX40/16, auto, 3:07's axles, 2" skyjacker lift, B&W flatbed

11-03-2009, 03:24 PM	#1 (permalink)
tmj_atx Newbie Join Date: Oct 2009 Location: Austin, TX Posts: 7 Thanks: 1 Thanked 0 Times in 0 Posts tmj_atx's Truck Pics	Jumping out of O/D Looking for a little guidance. A few weeks ago, my transmission began to hunt between 3rd and O/D. It got progressively worse over a couple weeks. This weekend, I started poking around and found the bolts on the TPS to be a little loose. Tightening those seems to have helped a bit. Now, it consistently shifts into O/D when it's supposed to, but if I'm doing anything over 40mph and ease up on the throttle (coasting, holding speed on flats, going downhill, etc, where I'm unloading the drivetrain) it drops down into 3rd. Apply throttle and it shifts back into O/D. I've started turning off O/D while driving around town at lower speeds to avoid the erratic shifting, but on the highway at 70mph, that's not really an option. Thoughts? Given that tightening the TPS made a difference, think my problem is there? PCM? __________________ 1991 D250 CTD 2WD, pump turned up, stock everything else, 250k miles on the truck, 40k are mine

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11-03-2009, 10:07 PM	#2 (permalink)
Philip 1ST GEN MODERATOR Join Date: Nov 2007 Location: Indiana Posts: 5,115 Thanks: 2 Thanked 131 Times in 121 Posts Philip's Truck Pics	Here is how to adjust the TPS. PDR Diesel Inc. The turbo diesel performance specialists! - 1st Gen TPS __________________ 93 W350 w/duals, fuel pin turned, 6X.018" injectors, 4" exhaust, 3" air intake horn, Super HX40/16, auto, 3:07's axles, 2" skyjacker lift, B&W flatbed

11-04-2009, 10:47 PM	#3 (permalink)
tmj_atx Newbie Join Date: Oct 2009 Location: Austin, TX Posts: 7 Thanks: 1 Thanked 0 Times in 0 Posts tmj_atx's Truck Pics	Success! Checked the voltage and it cycled smoothly, but at rest it was jumping back and forth from 0.35V to 5V erratically. From what I gathered, it looks like when I tightened it back down the other day, it was just slightly rotated such that if you call rest position 0degrees, it was landing at negative 1 or 2 degrees, and hitting 5V. The tolerances of the screw holes on the TPS is just large enough to allow for this to happen. Loosening the TPS and rotating it just a hair in the opposite direction did the trick. Road test was smooth as butter. Thanks for the info. __________________ 1991 D250 CTD 2WD, pump turned up, stock everything else, 250k miles on the truck, 40k are mine

11-04-2009, 11:16 PM	#4 (permalink)
Philip 1ST GEN MODERATOR Join Date: Nov 2007 Location: Indiana Posts: 5,115 Thanks: 2 Thanked 131 Times in 121 Posts Philip's Truck Pics	__________________ 93 W350 w/duals, fuel pin turned, 6X.018" injectors, 4" exhaust, 3" air intake horn, Super HX40/16, auto, 3:07's axles, 2" skyjacker lift, B&W flatbed