Needle become crazy! LX450

[at1992]

Hi,

My Speed needle become crazy and goes up an down like crazy.
Its happen when I put on D and let the truck drive by itself, or slow driving or when I hit a pothole. and I can feel the transmission shift back and forth also because of that! I assume that the speed goes crazy up so the transmission ECM try to shift. So When the needle go crazy I feel the transmission shift up and down instantly. What can be the cause?

Here is a video (this is me on Drive and let the truck drive by itself! No foot on the pedal.

 

[Rifleman]

I'm sure other members will chime in with more info, but IIRC this problem has something to do with your speed O sensor on your transmission. So start off by doing a search on Speed o needle bounce

 

[98 SNAKE EATER]

Make sure the ground behind the intake is properly secured.

I had the same issue after I did a valve job.

Speedo was dead, but would come to life every now and then when I hit a bump.

I had left the ground strap swinging

 

[pasquinel]

Make sure the ground behind the intake is properly secured.

I had the same issue after I did a valve job.

Speedo was dead, but would come to life every now and then when I hit a bump.

I had left the ground strap swinging

Hi,

My Speed needle become crazy and goes up an down like crazy.
Its happen when I put on D and let the truck drive by itself, or slow driving or when I hit a pothole. and I can feel the transmission shift back and forth also because of that! I assume that the speed goes crazy up so the transmission ECM try to shift. So When the needle go crazy I feel the transmission shift up and down instantly. What can be the cause?

Here is a video (this is me on Drive and let the truck drive by itself! No foot on the pedal.

where is the transmission ECM?