Got a slipping transmission in a newly acquired 75 D100. I am going to change the fluid and filter and adjust the bands. I have seen a method of turning the driveshaft until it stops and backing off the band adjustment. I have also seen the oem method of 72 in/lbs and back off. I have not seen for either method what gear the transmission needs to be in or if it even matters. So, this is my dumb question for the new year.

What gear do I shift the trans into when adjusting the bands?

there wouldn't be anything going on in the trans with the eng off so on the 72 in lb method for the two bands any gear selector position would work. I couldn't get to 72 INCH lbs & I knew something was wrong so I stopped & Kunkel had me set the lever where it contacts the center pin, that clearance to 5/16 & 1/4 (iirc) on a '66 904. I've heard of the turning method but don't know anything about it or pros/cons of either.

Leave the shifter in neutral and follow the factory service manual procedure for your truck for both bands Sorry for no links

Doesnt matter the gear. The tightening bolt is in direct contact with the band, which is hovering over the front drum at all times. 72 inch lbs comes up quick, and if you're using a click style torque wrench you'll barely feel it.

Which gear slips? Band adjustments will only affect 2nd or reverse if they're loose. If it slips in any other gears don't bother. You have another issue.
Doug

Well, I went ahead and pulled the pan, some metal flakes in it and some friction material, fluid dark pink, but not burnt. I put in a new filter and adjusted the low/reverse band using the tighten until the driveshaft doesn't turn, then bakc off 1/2 turn method since I didn't have an inch/lb torque wrench. Never got the driveshaft to not turn, but I didn't want to tighten the adjuster any more. Anyway, put it all back together go out for a drive, feels pretty good in reverse and first now, when it tries to shift into second it falls on its face and tries to stall the motor out. I am guessing the band is too tight. So ordered me an in/lb torque wrench and will be doing it per the manual this weekend, hopefully i can get the old girl moving. If that doesn't work, someone will be able to pick up a cheap 75 short bed soon!

Check the shifter linkage in neutral first and if the shifter arm to the tranny moves when you remove the linkage to it adjust it so it doesn't move at all by slipping it in and out Once you get neutral correct check it in 1st,2ndand 3rd gear also
It sounds like it is not adjusted correctly on the linkage, not the bands
BTW, I think the FSM calls for three and one quarter turns out from being bottomed out (72 inch lbs. tightening)on both bands

I agree with CAB, band adjustment is not your problem here.

72 inch pounds Is 8 foot pounds, is it not? Tighten the adjuster down snug with one finger until it stops, back off 2 turns and tighten locknut.

1970 manual says 2 turns,
I believe the mid 70's was 21/4 or 21/2 turns on the front band.

Cab, at 3 1/4 turns the band struts might fall out.

So much for the "turning the driveshaft" method.

1/2 turn is way too tight. The band is grabbing the drum before the clutches can release causing it to be in two gears at once. I wouldn't drive it again until you get the band adjustment right.

Pretty sure that's exactly what's happening.

I read it on the internet....

http://www.mopar1.us/band.html
Sounded logical, didn't work in practice.

Buy yourself a factory service manual and use that, not what might be accurate or not on the internet, their are some real goofs that post wrong stuff intentionally all the time
They are some real sick puppys

I, too, read that on the internet and it didn't make any sense from the gitgo. Way too many variables to make any sense of that.

Why try to reinvent the wheel?