I recently installed a new speedometer sensor and speedometer cable in my 1992 4x4. I thought everything was great until I started noticing how high the engine revs before the transmission shifts. I don't think it is shifting at the correct times. I read thru the FAQ's on the forum and have seen the diagram where the throttle cable connects with the cable which actuates the shifting in sync with rpm's. It seemed sraightforward that I should make an adjustment to the cable or replace the spring on the lever.
But I almost forgot that besides the speedo sensor and cable that I bought some nice tires secondhand. Stock tires are 205/75/15 and I mounted 235/75/15 ' s on the truck. I wonder if the change in the tires has caused the shifting to be out of sync. If that is the case - is the speedometer reading accurately?
How would I make adjustments so that it shifts at the right time and the speedometer is accurate while keeping the 235 size tires on the truck?

 

I just got threw putting 225's on the front and 30x9.5x15's (about 135's) on the back and I havent noticed a difference.

 

the speedometer will be inaccurate. i'm running 235's on the back of my truck and 225's on the front and my speedometer is off by 2mph. the best bet for the speedometer would be to take it to a shop(not sure how they fix it) or just drive past one of those police radar trailers and find out how much off it is(thats how i did it).

 

i put 30x9.5's all around. doesnt seem to effect the tranny much with over revving. clocking it with a gps and mph is off about ten percent, maybe a little less.

 

the shifting might have to do with the tv cable needing adjustment. the adjuster for it is on the trans. i just don't recall teh rest because i don't have an automatic anymore.

 

Don't forget that if the speedo is inaccurate, it'll be based on a linear curve. So it may only be off by 2mph when you're doing 40, but by the time you get to 70 it's off by about 7 or 8mph.

 

oh crap i forgot about that!!! that would explain why my speedometer said 65 and i was passing people left and right...lol

mine is actually off by 2 at 55mph, so when i do 55mph i'm actually driving at 57mph. 65mph is 68mph and so on.(I tested mine on a road that has the radar built permanently on the shoulder)