Switch pitch for a FSJ Jeep

Hello,
Newbie to this board, but not "Buick's" since Jeep used GM and Buick engines in the late 60's Jeep full sized Wagoneers and Pickups.
Anyway, I am working on the Jeep project, AMC 401 -> AMC pattern TH400, (TH400 with a AMC pattern from bell-housing) and am intrigued by the switch pitch TH400 setup, I don't know much as my research has just began, I have read though the service manual (thank for the guy who posted the service manual online) and some of the post here and else where.
(The guy's here seem to be the ones in the know, on switch pitch stuff)
I have a couple questions on availability, what stall speed and such converters are/were available, and if there is much still available.
The goal is to able get the engine into the power band at low speeds (climbing a hill, drag the boat out of the water, or just pulling out from the stop light, or such) and still be able to pull OK fuel mileage on the road (Highway), Well as good as a heavy Jeep can pull MPG numbers.
The control looks very straightforward, as this will be using a GM TBI so
I'll have VSS, TPI, RPM .. values all available, plan would be to use a piggy back micro controller to control the converter).
Any suggestions, as to what/where to look for parts, opinions on why this would be a good/bad idea are appreciated.

Thanks Mike D.

 

Thanks Larry,
Found those pages, looks like there are few guy's here that still support the switch pitch, from what I gather the SP was not used much by GM more for cost reasons rather than reliability or durability problems.
I think I am looking for the undesirable (from a go fast car perspective) 13" converters with a low stall, (how low can we go) and a medium speed stall, rather than the sorta high and real high the go fast guys need.

 

That is about the perfect area for what I was thinking would be good for a semi low RPM motor build (401 with a GM TBI, which is not going to be much of a RPM motor) should work almost as well as if it had the Buick 350 in it ( ) like Jeep built a couple years before this one.

 

One more quick question on the
64-65 vs. the 67, has is there any reasons to prefer the early vs. the 67 pump/input shaft ?

Thanks Mike D.

 

If you are looking to have a SP-T400 built I would have Jim W build you one... There are not many people who know the ins and outs of these trans!

Keep in mind you would need an adapter from a BOP case T400 unless you modify a Nailhead T-400 to have the SP feature.

http://www.v8buick.com/forumdisplay.php?f=100

 

The expert converter rebuilders can machine the startor to go to a higher
"high" stall than stock. Low stall and your economy is unaffected. I have
used both, and I highly recommend the higher high. Bruce Roe

 

The plan is to stuff it in all in a AMC/Jeep pattern case ( From the reading I think it should all be good, but my thinking has been known to be flawed from time to time)
With a GM NP203 (short-short output shaft) to mate with a GM-241C T-case.
(Pretty much stock Jeep, everyone Else's parts, with a little gunk to hold them together).

I am currently running the output side, looking to make the truck a little more versatile.

 

Before you attempt to install the VP parts, make sure the Jeep case has the fluid passage shown here. If it does, you'll have to press in a plug similar to Delco #8611710 with a 0.038" orifice drilled into it for restricted flow. Without this passage (it seems some cases do not have it) and the 0.038" restriction in it, the variable pitch will not function.

Devon

 

Thank you Devon

I read about the bleed back passage, but was not sure exactly which of the passages / holes in the group that I needed to check for. I have to get the organ donor down to take a look to be 100% sure, from the Jeep service manual it looks good (But it is a Jeep service manual, which may have ripped off the pictures from a GM manual for the tranny rebuild section)

Mike D.

 

I think we are good to go as far as the case is concerned, the bleed hole seems to be correct.

 

I have seen a couple versions of the bleed hole restrictor. The
factory restrictor is sheet metal much like the fuse end cap, with a
.026" to .028" dia hole. A replacement I bought (KB?) was made
from a machined rod, the hole was a generous .078" DEEP and
.035" to .0385" dia. I hope they are equivalent, more depth
needs more dia.

Bruce Roe

 

That makes good sense to me. When I rebuilt my transmission in the late '80's, I used a later case which had the snap ring for the center support and I tapped the passage we're discussing a short depth to receive an allen-keyed set screw with a 0.040" hole drilled through the center. I don't know the actual length of the orifice in the set screw.

With that arrangement the transition from high to low stall is very quick; quick enough that given some generous part-throttle acceleration, the 225-70 radial tires I used to have on the car would lose traction for just a moment during street driving before the shift to second gear.

Devon

 

Thanks guy's,

I like the set screw idea, drilled with #65 (0.035") ish +/- drill. (On slippery stuff or running a side hill hard shifts, do add excitement but not in a good way )

Now to get a firm handle on the stall speed's choices, (I assume not many).
I am having to hard time finding a consistent cross check-able source for stall speed info, I have seen spec's all over the place as far as values go, in my web searches, called at least one manufacture, (they list a part #)
but nothing so far in finding some hard data.
(I realize stall speed is a terrible way to spec. a converter as there is no base as to the torque value at which it is measured, but it is the only game in town, we have)

 

Actually the cases are the same, though the older ones may show
wear. The center support that goes in gets thinner for the .040"
seating ring. From memory the "teeth" are .333" thick on newer,
.373" thick on older. I have a bunch of the older I'm hoping to
machine off the extra 40 mils. Bruce Roe

 

So a larger hole gives a quicker transition to high stall, guess I ought
to try that. Trouble is with too big a hole, you'll have high stall about
all the time, and each experiment involves complete dis assembly of
the trans. Oh well, not too hard with a lift.

Perhaps I'll try making some of the drilled 1/4" aluminum rod restrictors,
used mine up. Haven't found a source of plain 1/4" plugs yet, they must
be out there.

Bruce Roe