When I start my truck the rpm's bounce alot as in 1000-2000 then slows to 1000-1200 then back to the big bounces truck doesn't have a cam or any power adders. This only happens on the gauge the truck doesn't fluctuate at all. 1990 f350 crew cab long bed 460 E4OD.

Could this potentially have any link to my trans not shifting properly?

 

On this vintage truck you simply have a bad tachometer, if you source another gauge cluster with a tach from an '88-91 V8 gas truck the tach portions will swap in without changing the whole cluster. You just have to remove the trim around the dash and cluster, remove the clear cover lense and then unplug the tach and swap it, easy 10min job.

If your truck also has trans issues pull the codes and post up what you get, that slushbox is 100% computer controlled and any code problem can result in strange trans behavour.

 

Conanski thank you for the reply, I figured it was just worn out glad to know it's an easy repair and not something far more in depth. As for codes I only have one constant code 95, and which ever it is for egr due to it not being connected. randomly a code 18 for the spout.

 

If your rpms were actually fluctuating it sounds to me like it would be a TPS. I don't know about these trucks but on my jeep the rpms would fluctuate and the trans would shift funny. Don't know if it's worth trying, but if they cheap enough why not?

 

The_drew I may look into this thank you.

So just for fun went out to do a KOEO got codes.
95, 18, 33.

41, 95. In the CM codes this truck loves to fluctuate.

 

Had a longer break for lunch today so I ran a KOER test since the truck would be warm and it gave me another check engine light while driving.

Codes 41, 18, 33, 77
I never know when to go wot so I always get this one but how do I fix the others?