Recentley put 2'' bigger than stock tires ,14"open element,3' cat back on 90 fullsize 5.7,3.73 gear.Truck seems to shift before reaching powerband at part throttle.Truck has 86,000 miles never been into till recentley with above mods.I think tv cable has never been alterd.Would shift kit wake this truck up? Is the ECM not liking the changes made?

 

Did you recalibrate the speedo? If not, that could be the cause.

 

To restore the shift points you will have to adjust the the tranny governor. Its directly affected by tire size and axle ratio.

Really you should post this on the trans/drivetrain board.

 

the governor is nto effected by gear or tire. it is an internal device. the thing about governors is that each tranny is a little different. if you put yours into the one you got from teh truck it may get it back to teh way it used to shift, or close at least.

later
tim

 

People have said this before. I can't understand their reasoning. The axle ratio won't do anything to the shift point of your transmission. It should still shift at the same engine RPM's that it always has. Now the actual MPH speed shift points will be different, but that is unvoidable.

 

Yeah i saw this came up on wrong board,not much forum experince.I guess by adding the taller tires 32'' ive got about a 3.40 or so gear now.I can really tell the diff.Any ideas on getting that umph back on the cheap,and still keep my new tires?

 

The governor is driven directly by the trans output shaft. Output shaft speed at a given road speed is directly related to tire size and axle ratio.

He increased his tire size and now the output shaft is turning slower. Thus the governor is turning slower and causing the trans to shift sooner.

To raise the shift points back up he needs to change the weights on the governor.

 

Try adjusting the TV detent cable and see if you can manipulate the setting to the way you want it.

 

The output shaft speed and the Engine speed should have the same relationship they have always had. No matter what the axle ratio or the tire size.

 

I agree the only thing I can think is that the pedal is being pushed farther now due to decreased mechanical advantage. This would make it shift differently. I notice that my tranny snaps into gear better if I don't have much pressure on the pedal, like if I back off the throttle to make it shift.
You'll probably never get it exactly the same, but adjusting the tv cable would be a good idea to try.

 

For the sake of arguement, decreased mech adv would be the same as adding say 500lbs of payload. The increased throttle application required to accelerate the same as without the payload causes the trans to shift later not sooner like K5guy is talking about.

Changing the TV cable is NOT the answer. More than one or two click tighter than spec and the cable tends to readjust back to spec or bend the brackets/hardware when you hit WOT. Looser makes it shift softer and sooner and runs the danger of harming the trans due to inadequate line pressure.

The TV cable should be synchronized so that at WOT both the butterflys are open fully and the TV cable is pulled out to its travel limit. Neither should have slack to move farther.