Under load is the only constant (towing a trailer).
Intermittent at best sometimes 2-3 or 3-4 never into od or out of first.
Basics done fulid full and clean. Plug clean and seated good.
No codes or flashing od light and no cel.
Thanks guys for ideas

 

FYI, 4 is overdrive. Torque converter lockup could feel like a 5th gear to some.

Perhaps boost leak in hose to MAP sensor?

Is the speedometer steady or bouncing?

Are the Brake lights working, even third light behind cab?

Any of the brake lights using LED bulbs?

Is the cruise control working?

Any trouble starting with the shift lever in Park sometimes?

Other smarter people will be along soon to help better.

Kevin

 

Speedo bouces when bump hit hard never matched to the hard shift ie at same time.
Up pipes tight and has mew manifolds on it.
Body swap this past winter.
Map hose ok
Lights all ok no led on truck or trailer
Cruise works except with the hard bumps and speedo bounce
Park interlock works fine

Thanks kevin for the fast response
And to all for the info

 

Wow expected more than just the one response

 

Sometimes I do other things.
I think those two are key. If the vehicle speed signal is erratic it will cause all kinds of problems.

 

Have you replaced the VSS? Sometimes that sensor is the culprit for a bouncy speedo.

USE OEM

 

Sorry I didn't get back to you earlier, but Mark and Jarrett have headed in the right direction about checking the VSS in the rear end to be the first place to look. Be sure to check the wiring there too.

When you did the body swap, did you have the instrument cluster in the dash unhooked?

Kevin

 

Ya vss changed. Put old back in as there was no change