Dave_1972
New member
- 23
- 0
- 1
- Location
- Wooster, AR
My 77' M880 is experiencing problems when shifting under heavy load.
The symptoms:
When gently accelerating up to 55-60mph the tranny will shift normally at all three gears.
When rapidly accelerating up to 55-60mph it will shift late and sometimes doesn't want to shift at all. In fact, I have found that when I feel the truck is past it's natural shift point and the RPM's start to get hairy I can ever-so-lightly ease up on the pedal and the tranny will immediately shift. Sometimes it will happen at the 1st-2nd shift (but it is always an abnormally late and awkward shift under these conditions) but it will happen every time on the 2nd-3rd shift.
I am reading conflicting info on the net about how this works. Should the M880 have a Throttle Valve that controls the shift point and is affected by vacuum?
If so - what is the procedure to inspect/replace/rebuild it?
Thanks for the help.
The symptoms:
When gently accelerating up to 55-60mph the tranny will shift normally at all three gears.
When rapidly accelerating up to 55-60mph it will shift late and sometimes doesn't want to shift at all. In fact, I have found that when I feel the truck is past it's natural shift point and the RPM's start to get hairy I can ever-so-lightly ease up on the pedal and the tranny will immediately shift. Sometimes it will happen at the 1st-2nd shift (but it is always an abnormally late and awkward shift under these conditions) but it will happen every time on the 2nd-3rd shift.
I am reading conflicting info on the net about how this works. Should the M880 have a Throttle Valve that controls the shift point and is affected by vacuum?
If so - what is the procedure to inspect/replace/rebuild it?
Thanks for the help.