Have a 95 5.0 rwd 4r70w 3.55ls rear. Have an erractic speedo when over 40mph. replaced both speed sensors dont see any shorted wires. Decided to look in the diff do you think the flat tooth is bad enough for that?

 

No, but whatever flattened that tooth is probably still bouncing around in the differential. I'd open it up & inspect.

There is only 1 speed sensor for the speedometer, and it's the ABS sensor in the rear axle. And since neither one was causing the problem, I'd put both originals back in the truck. Read this page:

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I guess ill go pull a test cluster then. Probably still gonna rebuild the rear just to swap gear ratios.

 

Pulled 2 cluster from the junkyard 1 from a 94 the other from a 95 both have the same problem at the same speed so unless i got 2 bad ones i guess that tooths gotta be my problem

 

Same issue in my 96 F150 with 4.9L and E4OD. Swapped tone ring, speed sensor, PCM, and had Speedometer "refurbished". Same problem. Truck runs great, shifts great up to third gear, starts to bounce at 35mph and if I accelerate up to 65-70 it will do erratic shifting. Pulling my hair out cause I even had the transmission put on a tester and they said it was in great shape and recommended the PCM or Speedo. ANY HELP WOULD BE GREAT! Before I am completely bald!
Note: I have tried 3 different speed sensors and also swapped out the speedo with a junk yard dog. Put old sensor and speedo back in as neither helped.