Won't Shift into Overdrive

D

davisca455

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Nov 25, 2010
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Davis, CA.
Monday the 20th:
Double failure. 4wd actuator toasted and trans wouldn't shift into OD. These failures appeared to happen at the same time?
Tuesday the 21st:
Had the actuator replaced which cured the 4wd issue. A quick check confirmed that the trans shifted into OD.
Friday the 24th:
Trans no longer shifts into OD. 4wd still working.

Chris,
'92 3/4 Ton Suburban
5.7L, 4L80E
 
davisca455 said:
Monday the 20th:
Double failure. 4wd actuator toasted and trans wouldn't shift into OD. These failures appeared to happen at the same time?
Tuesday the 21st:
Had the actuator replaced which cured the 4wd issue. A quick check confirmed that the trans shifted into OD.
Friday the 24th:
Trans no longer shifts into OD. 4wd still working.

Chris,
'92 3/4 Ton Suburban
5.7L, 4L80E
Click to expand...

Start with the simple first and check TPS for smooth and linear electrical response over the entire range of motion. If not, replace. The other area that wold cause this is the brake pedal switches improperly adjusted (always on), TCC solenoid failed (easy fix in the pan), TCC clutch worn out (must remove trans and replace TC). TCC = Torque Converter Clutch

Keep us posted, but from that you have described. It most likely a wiring issue to your TCC since you have worked on getting your actuator replaced.
 
I just drove the 'Burb for the first time since my last post. No changes were made and now the trans shifts into OD with no issues. I'll check the TPS tomorrow and report back with any info. I wonder if a marginal TPS can be affected by temperature?
 
davisca455 said:
I just drove the 'Burb for the first time since my last post. No changes were made and now the trans shifts into OD with no issues. I'll check the TPS tomorrow and report back with any info. I wonder if a marginal TPS can be affected by temperature?
Click to expand...

Yes temperature can play a roll on your TPS or a little play. Keep us posted and here is a link that should help you since your have a 1992.;)

Keep us posted and be safe. http://www.troublecodes.net/GM/
 
Replaced the TPS last week.
Just completed the test drive to the Sierras this afternoon.
The 'Burb was a Beast going up the mountain today!
No problem keeping it at 75mph going up the passes today.
Thanks Molson.
 
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