Hi, great forum. I have a 97 4x4 extracab with 4.6 and autotrans.
when i hit 60 or 70 mph the overdrive light starts blinking on and off. The truck runs great and shifts properly. I had a friend at his shop scan it and I get a vss intermintent code. we installed a new speed sensor but still have the problem. Help

thanks

 

Hi sodbuster1939 and welcome to FTE

Do you remember what the code was? P-something probably.

 

yes, the two codes were P0503 and P1500. I took the truck out on the road with the scanner attached and held the sppe at 70 mph. The MPH on the scanner fluctuating from 70 to 61 to 75 to 58 etc.

 

Both those codes are for the VSS or wiring to it.
Did you replace the VSS on the top of the rear diff housing or the one in the back of the transfer case?
It is the transfer case one that you need to look at.
Most of the time people forget about that one when they think VSS

 

thanks for all your help, I changed the vss thats on the tail shaft of the transmission behind the transfer case is this the one you call behind the transfer case? and theres another one on the differential housing?

 

The VSS in the rear diff housing is for the ABS.
You replaced the right one
Next step is probably to remove the extension housing and see how tight the drive gear fits on the output shaft. If it wiggles around or is worn it will create bad VSS readings.

 

thanks again I will check that out. this is what I get for selling my 56 f-100. I new I was in trouble when I couldn't find the sparkplugs. Your coments on how to change plugs and wires were right on the money. Who ever had the truck before me must have thought it was a 7 cylinder. never changed the last plug on passenger side gap was about half an inch.

 

inside the tail housing is a plastic gear that turns the vss if it is worn in the center it will mess w/ ur read out i replaced my vss 5 times before i figured that out

 

thanks for your help. I will have our dealer get me a gear.