front band adjust on 47RE...

[rotohead]

opinions on why there are many different instructions on the amount of turns to back off the adjusting screw?
Everyone says to torque to 72 in lbs and the FSM says to back 1 and 7/8 turns (really, 7/8's? is that metric or standard?) but I've seen anywhere from 1.5 to 2.5 or even 3. Just curious. Everyone seems on the same page with the rear adjust, book and all others say 3.

 

[JR]

1-7/8 is just that, one full turn and another turn half way between 3 o'clock and 12. As long as it is close you are good.

Re reading your post it seems there is some confusion. Per my 98 FSM, torque to 72 in lbs then back off 1-7/8 turns. I would not pay attention to anything but the FSM.

 

[rotohead]

Let me clarify. If you watch utube, download written instructions from transmission builders or look for recurring maint on the 47RE you will find many different ways to adjust that front band. As is clear the FSM states 1 and 7/8 turns. I've seen elsewhere that says to go anywhere from 1 and 1/5 to as much as 3 turns. Given there may be bands made now a different way, different manufacturers or aftermarket upgraded bands I was wondering if anyone had more knowledge on this. Maybe some trans builder uses a band with different material on the contact surface that requires the 2 and 1/5 adjustment. Just asking .

 

[JR]

Bands are made to factory spec. Im not sure I've seen anything else, if you have a custom trans that is built to different standards I'd follow their spec otherwise stick to FSM.

 

[Timd32]

if you have a custom trans that is built to different standards I'd follow their spec

On point!

Yeah, the spec I was given

Front: 2 1/4 Turns
Rear: 3 1/4 Turns

But mine is not stock so going by the build sheet they gave me. So do not follow my lead, my band was a raybestos stock band from what I could tell. I should have taken a pic of it before I put them in, thought about that like 20 min after I finished. Just to look up the part number and see what I put in there.

 

[cerberusiam]

opinions on why there are many different instructions on the amount of turns to back off the adjusting screw?

Because the band, the age of the band, and the build dictate what is the optimal setting. Flex bands stretch with use, front servo design, pressures and band lever dictate different settings. Start with factory setting then adjust for shift feel.

 

[rotohead]

Because the band, the age of the band, and the build dictate what is the optimal setting. Flew bands stretch with use, front servo design, pressures and band lever dictate different settings. Start with factory setting then adjust for shift feel.

Yes, that's what I was looking for. Very interesting. You say adjust for shift feel. Would that be tighter for a slightly firmer shift?

 

[cerberusiam]

The 2-3 shift is where the band adjustment causes issues because it is such a complex interaction. That band has to hold until the direct clutches apply and release fast enough it doesn't cause a bind. Too tight and you get a bind up on the 2-3 shift, too loose and you get a cut away shift. Mess with the front servo and not change the apply lever and it will never feel right. Everyone wants the super servo because it has more area to apply faster and hold better but if you do not change the lever length and adjust the direct clutch clearance and\or adjust spring pressure or release flow you get weird shifts at inopportune times.

Flex bands with too much pressure and you rip the rivets off the band mount, stretch them out so the adjustment is gone, etc. Simply adding a shift kit will change the way the shift feels. You just have to tighten and loosen it to find the sweet spot so it works across the rpm range.

 

[fest3er]

The 2-3 shift is where the band adjustment causes issues because it is such a complex interaction. ... You just have to tighten and loosen it to find the sweet spot so it works across the rpm range.

Should it be smooth regardless of input torque/HP? Or might you expect the 2-3 shift to feel perfect at max torque but bind a little at idle? Or feel perfect at idle but slip a little at max torque?

 

[cerberusiam]

That is all in the setup and tuning as the TV valve will control the pressure at light and heavy throttle. Everything being equal it should feel good at light and heavy throttle if the timing is correct. Ideally, a little loose under hard throttle and the clearances tighter on the direct clutch pack to keep away from bind up. However, that then translates to a lot of heat in the direct clutch pack when it hooks and the more TQ you run thru the worse it is. When you go away form the stock setup and stock TC it really puts a strain on the other components and finds the weak spots.

Set it for more slip and no bind up so you have to use the right foot will save the parts.