Modifying Transmission Shift Points

[BBeach]

Properly setting or calibrating it (what ever you want to call it) raised the rpm shift points of mine noticably. All I can figure is the prior owner had worked on the transmission and I guess he forgot to set or do the cable adjustment.

The manual says with the engine off, to push the cable release button, retract the cable self adjusting mechanism all the way (push the cable plunger inward), then release the button, then open the throttle body to wide open, then press the button again, then release the button then release the throttle and you are done. The mechanism self adjusts using this procedure.

Yeah I did that yesterday and didnt notice much. I heard quicker shifts are better for the transmission too because of less time in between gears.

 

[peeweexj]

The Throttle Valve (TV cable) will firm/soften transmission shifts.

There is a button on the cables bracket, if you push down on this, you can slide the sheath/case/housing for the cable. If you slide it towards the throttle body, the shifts will be softer. If you slide it away, the shifts will be firmer/faster. If you adjust it too firm, you will not be able to get to full throttle, because you will bottom out the TV cable.

 

[peeweexj]

Quicker shifts are not always better for the trans. They can reduce heat, because of less slippage, but they can also put more shock loads on the internal parts.

 

[BBeach]

The Throttle Valve (TV cable) will firm/soften transmission shifts.

There is a button on the cables bracket, if you push down on this, you can slide the sheath/case/housing for the cable. If you slide it towards the throttle body, the shifts will be softer. If you slide it away, the shifts will be firmer/faster. If you adjust it too firm, you will not be able to get to full throttle, because you will bottom out the TV cable.

Yeah I noticed that yesterday is that i'll stop short of full throttle so if you try mashing the pedal to the floor somethings going to snap....and my best guess would be the internals of the plastic TPS which is why i was wondering of a software mod to the TCU or something that is reversible.

 

[BBeach]

Quicker shifts are not always better for the trans. They can reduce heat, because of less slippage, but they can also put more shock loads on the internal parts.

I agree on that too, say with a standard, dropping the clutch puts a lot of stress on the internals and it gives less time in between gear changes for the change in momentum of say 3400rpm to 2000rpm in the next gear whereas letting the clutch out slower gives it a slower change and less stress. It doesnt matter so much at higher speeds because the changes rpm diffs between the gears are 25% or so and the "tranny side" as so much momentum that the engine just gives in. Dont know if that makes sense at all. :dunce:

 

[Blaine B.]

Found it online

http://autorepair.about.com/library/faqs/bl576b.htm

Apparently adjusting it like this is the "factory" method......not too firm and not too soft?

I'll be adjusting mine in a few minutes-

 

[Blaine B.]

Cable button was pressed and the sleeve was pushed in all of the way-

Then, the throttle was opened to 100% and the cable was adjusted.

You can adjust the cable so that it sticks out a bit further - but you really can't do it so it doesn't stick out, because as soon as you do a "wide open throttle" it'll adjust itself anyway.

 

[BBeach]

Yeah but like I was saying before, if you adjust it the wrong way its either going to be too smooth/slow or somethings going to give, either the thing that locks the cable at that position, or the TPS....

 

[Blaine B.]

I never noticed that button until I read this thread....never payed attention

 

[lawsoncl]

Yeah but like I was saying before, if you adjust it the wrong way its either going to be too smooth/slow or somethings going to give, either the thing that locks the cable at that position, or the TPS....

The adjustment method is to push the button and push the sleeve in, then press the throttle full open which causes the sleeve to ratchet out to the proper place. So adjusting it too tight won't break anything, as it will snap back out to the proper place next time you hit WOT.

The cable controls the internal hydraulic pressure in the tranny based on throttle position, hence controlling the quickness and firmness of shifts. Having it adjusted too loose can cause sluggish shifting and readjusting can make the shifts happen a little quicker. The trans computer is still starting the shift at the same rpm, but if it's completing quicker it can seem like its shifting at a lower rpm.

 

[Blaine B.]

Right, I was just saying you couldn't permanently keep it adjusted "too far in"

 

[BBeach]

Im just saying when I had it pushed in a little bit, the farthest the throttle body went was say 80% WOT, and if I tried to push it a little further (not pressing the button) it wouldnt ratchet at all, and I didnt want to chance breaking the internals on the tps seeing as I tried this before with a spare and it broke it? Sure if you press the button in while holding the pedal down, I tapped the button and it would ratchet one click out for every quick push of the button. So what you're saying is that you set it in too far and you can just mash the throttle and its going to slide out? (without hitting the button as in normal driving?) It'll prolly slide out but Im not going to try it with my good TPS.

 

[Ecomike]

Im just saying when I had it pushed in a little bit, the farthest the throttle body went was say 80% WOT, and if I tried to push it a little further (not pressing the button) it wouldnt ratchet at all, and I didnt want to chance breaking the internals on the tps seeing as I tried this before with a spare and it broke it? Sure if you press the button in while holding the pedal down, I tapped the button and it would ratchet one click out for every quick push of the button. So what you're saying is that you set it in too far and you can just mash the throttle and its going to slide out? (without hitting the button as in normal driving?) It'll prolly slide out but Im not going to try it with my good TPS.

The older renix years do not seem to ratchet, my 87 Renix does not ratchet either. The rathcet feature must be a new model '91 and up (?) feature. The Renix ones require that you push and hold the button while opening the throttle to WOT.

 

[Blaine B.]

Maybe. If it won't ratchet out when you manually press the throttle, don't think it will by mashing the pedal.