good idea! one thing you have to keep in mind is that you'll of course have to run a special converter, and when you run with the switch pitch "on", the converter and trans will run a LOT HOTTER!

 

good idea!

So it does sound like it would be worth the effort? I've got to pull apart my tranny anyways so that is why I've given it some thought.

one thing you have to keep in mind is that you'll of course have to run a special converter, and when you run with the switch pitch "on", the converter and trans will run a LOT HOTTER!

I knew I forgot something in my original post Yes, I did know about the torque converter.

I'm not overly suprised about the heat issue. OTOH, if the tranny cooler circuit is in good condition, this shouldn't be an issue should it? I intend to put a huge tranny cooler with a fan on my tranny.

 

sounds good.

you might want to double check about the case and valve body. i know for a fact that they are different (along with the pump and a few other knick-knacks), but i do not know if the "normal" 400 case can be converted to switch pitch or if you have to replace the case with the switch pitch model. same goes for the valve body.
PS: and i can get you the parts and converter to rebuild it

 

The few articles I've read said any 400 case can be converted for the switch pitch... something about an oil galley.

Speaking of rebuilds... do you think the price of a rebuild kit would be more? I would assume the torque converter would be more... just curious about the rest of the case

 

carefull what auto your looking at just cuz it has two leeds coiming out of the tranny does not mean it switiched pitch. some 400s had a second leed for TSC

yes you can convert a fixed pitch auto to a switched pich auto very easly

Kenne-Bell use to sell the kit for this (maybe they still do)

it consisted of a front pump, input shaft and some other small parts for the conversion

 

Any auto has "switch pitch" capabilities from the get go. It's the switch next to skinny pedal.

Not to be a smart ass, but having wheeled my Scout with both 2:1 and 4:1 in the t-case. When geared with 2:1 I used more brake to get the torque mulitplication I needed, compared to what I need with the 4:1 t-case. I also got more heat when using the brake to control slip. Sounds like a lot of trouble for something you can do with your free clutch foot.

 

carefull what auto your looking at just cuz it has two leeds coiming out of the tranny does not mean it switiched pitch. some 400s had a second leed for TSC

Cheif, the almost sure fire way to tell is to look at the oil pan of the transmission. If it has a "shoe heal" in it and the tranny has the two wires, one can be 99% certain it is a switch pitch. I've done some junkyard scavaging and seen about three of them in the right year vehicles

 

hmmm

for a site

The converter changed stall speeds from 1800 rpm to 2600-2800 rpm

dont know if this is a benafit

 

Any auto has "switch pitch" capabilities from the get go. It's the switch next to skinny pedal.

Not to be a smart ass, but having wheeled my Scout with both 2:1 and 4:1 in the t-case. When geared with 2:1 I used more brake to get the torque mulitplication I needed, compared to what I need with the 4:1 t-case. I also got more heat when using the brake to control slip. Sounds like a lot of trouble for something you can do with your free clutch foot.

I definately understand what you are saying here. I'm just hoping to get every advantage I can on my latest(and last) buildup.

As it is, I'm going to have an NP203 GRB after the 400

I figure if I can get the switch pitch stuff for cheap enough and install it while I have the tranny torn apart, I'd be ahead of the game.

FWIW, I've been on the "just not quite low enough" end of the stick a few times and if I can use this to get over the hump, it is one less thing to worry about in the future

 

hmmm

for a site

The converter changed stall speeds from 1800 rpm to 2600-2800 rpm

dont know if this is a benafit

See my first post Apparently when it is on, your "effective gearing" is 2.6 to 1 lower rather than the normal 2.0 to 1 when it is off. So in theory, it would crawl a bit better.

But as Georg has pointed out, the cost is added heat.

I'm just weighing my options right now. After my less than stellar experiences with a 700r4, I'm trying to get every advantage I can with my 400

 

I know your trying to push the envelope here, but is this an area you want to try? Either holding the brake or running the variable TC switch thingy will have the same results. Lower effective ratio and more heat. However do you know how well the "switch thingy" is going to hold up in real world wheeling? What's going to happen when you suck air for a few seconds, or going back and forth between reverse and drive? I'd rather go a little lower in gearing then risk not having a running tranny on the trail.

Is there another approach to take, what does the switch do exactly? Does it hold a band or let one slip, maybe something you can replicate with a custom TC or valve body work?

 

I know your trying to push the envelope here, but is this an area you want to try? Either holding the brake or running the variable TC switch thingy will have the same results. Lower effective ratio and more heat. However do you know how well the "switch thingy" is going to hold up in real world wheeling? What's going to happen when you suck air for a few seconds, or going back and forth between reverse and drive? I'd rather go a little lower in gearing then risk not having a running tranny on the trail.

Is there another approach to take, what does the switch do exactly? Does it hold a band or let one slip, maybe something you can replicate with a custom TC or valve body work?

I've got the lower gearing taken care of.. I'm going to run a NP203 GRB in addition to a regular transfer case(ie an extra 2 to 1)

The switch pitch is actually a "special" torque converter that has two stall speeds(1800 and 2800 I believe) which is electrically actuated. This is also why it is called variable pitch. As far as I've seen, it is a different pump, input gear, and torque converter as well as some wiring. No special bands, clutches, etc(ie regular TH400 parts from the input back). I can still do all the fun TH400 upgrades I want.

The "biggest" benefit of it is the ability to get a lower crawl ratio without having to shift into neutral first(ie switching the tcase into a low gear). Basically, I can go from a low range of 97 to 1 to 126 to 1 at the flick of a switch(based on the torque converter multiplier of 2 to 1 for normal and 2.6 to 1 for "on") The other benefit is not burning up the brakes by riding them.

As for the durability, the switch pitch is used by some people in racing behind big block caddy's(ie at least 400ft/lbs of torque in stock form) so I think it would hold up to wheeling... especially with a larger tranny pan, and a "high capacity" cooling circuit.

As for why I'm considering this approach, I've got a couple of reasons:
The most important reason being I want to ensure I'll be low enough. Since I'll have the tranny ripped apart for a new output shaft, I figure for another $50-$100, I can help my low range a bunch without killing my highway driving.

The other notable reason is it is going to go in a show-n-go rig. Think along the lines of Marlin and his 1000 to 1 crawl ratio. Needed? Hell no. Cool? Absolutely What can I say, my rig is my toy and toys are for fun

BTW, I'm not trying to push the envelope at all.... I'm trying to think outside of it I'm not afraid to spend a little money on an experiment. I've done it before, failed, but learned a shit load from it.

 

dont mean to be a prick but if ya dont know how it works then how can you say if it will hold up or not

from my "How to work with and modify the Turbo Hydra~Matic 400 transmissin" book


"Switch-pitch convener operation
Variable-pitch stator hladcs pivot on their carrier ring and huh. The blade pivots arc located so the force ofvortex fluid flow holds the blades in their high-stall, high-angle position.
Each stator blade has a crankpin which engages the same hydraulic piston. The pis ton is located in and is concentric with the stator huh When the piston is pressurized, it rotates the blades to their low-stall, low-angle position.
A passage in the front pump bleeds off some converter charge oil to operate the sta tor piston. Fluid flow into this passage is controlled by a stator control vaive, which, in turn, is controlled by fluid in a separate passage.
To pressurize the stator piston and rotate the stator blades to their low-stall position, a 12—volt solenoid closes a tapered valve on its seat. This blocks fluid that was returning to the sump through an exhaust passage, grad ually appl 150 psi ofpressure to the sta tor control valve. The stator control valve moves against a spring and opens the stator piston fluid passage. This allows fluid to flow out the front pump, down between the input and stator shafts, and into the stator piston chamber inside the converter. Fluid pressure nu)ves the piston and stator blades against a stop, to the low-angle, low-stall position.
"


Lil'John I say go for it and let us know how it turns out

looks to be a very simple conversion and if it doesent work out is about a days time to put back the fixed pitch guts

 

thers one for sale on ebay
http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=1874818273

jdjanda

read up

http://buickperformance.com/switchpitch.htm


:edit: a sweet write up

http://www.bdub.net/tranny/SwitchPitch-StreetRodder-5-77-text.pdf

 

Hell good tech for a change :beer: Good to know the extra slip is not from clutch material. Then back your orginal question is it worth it, hell yes. There is always one line you could have taken if you'd been a little lower

Joe

 

Hell good tech for a change :beer: Good to know the extra slip is not from clutch material. Then back your orginal question is it worth it, hell yes. There is always one line you could have taken if you'd been a little lower

Joe

using the term "slip" is pushing the envelope

some more info

"At low speeds, such as when towing up grades, switching to high stall will increase engine speed to a better power range and provide additonal tourqu muliplycation. when descending a steep grade additional engine braking can be gained by switiching to low stall"

 

Cheif,
No offense taken. I knew how it worked... I just didn't feel like typing all that up:flipoff2: Plus, some get pissed when I get too verbose

Also to add to your list of tech articles:
http://www.442.com/oldsfaq/oftsp.htm

I already had the buickperformance link

Joe,
I probably will go with it... but it will have to wait until after Christmas.... I have to pay for a rebuilt engine first With luck, I'll have the rig running by the end of winter

 

Cheif,
No offense taken.

it was toward jdjanda

i figgured you knew how it did it thing
:goofball: :goofball:

thanks for the link

 

let's just get one thing straight: the switch pitch does not magically give you a 2:1 reduction. it merely increases the stall speed of the converter from somewhere around 1600rpm to roughly 2800 rpm.
the conveter torque multiplication is about 2.5 to one but as the name states, it's TORQUE multiplication, not gearing you're getting!!!!!!!:flipoff2:
ps: you get torque multiplication with any auto, no matter the stall.
PS #2: what the hell is wrong with th700s?

 

PS #2: what the hell is wrong with th700s?

I woulnt feel safe depending on a transmission that was built for a power-wheel :flipoff2:

and the USS Enterprize can keep its warp drive

 

let's just get one thing straight: the switch pitch does not magically give you a 2:1 reduction. it merely increases the stall speed of the converter from somewhere around 1600rpm to roughly 2800 rpm.
the conveter torque multiplication is about 2.5 to one but as the name states, it's TORQUE multiplication, not gearing you're getting!!!!!!!:flipoff2:
ps: you get torque multiplication with any auto, no matter the stall.

Georg,
Thanks... I meant torque multiplication... but it does modify one's effective crawl ratio which to some is the magic number.

PS #2: what the hell is wrong with th700s?

Personally, I've never had any luck with those POS's. For me, it didn't matter if it was a factory rebuild with all the "upgrades" or rebuild by a builder... I still blew 5 or 6 of them behind that high horse power 2.8L Chevy engine And not one lasted more than 20k miles.

Thus, for me to feel comfortable with one in a vehicle, I'd end up spending $2k+ on a rebuild Plus, in my application, an overdrive won't be needed but bullet proof is... I've got enough power on tap to pull 37's with 4.11 gears(or the eventual 3.33's or 3.73's I'll eventually goto) Plus I've got an NP203 gear reduction box to handle the crawling.

 

yeah, yeah, i know, 700s got a bad rep when they first hit the road in the early 80s, but for you to kill a few of them behind a 2.8 is pretty odd. either whoever built it has no frickin clue, or you have other issues (cooler, linkage, improper throttle pressure,.....)

i for one am putting one in my 45 wagon and in my wife's fj60.
i have 3 close friends that run these transmissions behind 350 tbi motors and they have not had any problems, even after 40k plus miles.

 

ps: and my ex room-mate runs one in a 91 chevy extracab with 1 ton axles and 38 inch swampers, lockers,........
so don't tell me that 700s are crap!:flipoff2:

 

Georg,
It didn't matter who built my 700R4(5 different tries). I got a dealer one in 95 or so. I also ran a heavy duty cooler, had the kickdown set at the dealership, etc,etc,etc. In fact, the one I got from the dealer was not a rebuild of the one I exchanged it for.

As the saying goes, some people have luck with them, some people don't.

Unfortunately, I'm one of those that had EXTREME bad luck with them.... so bad that I'm just now considering an automatic(I've not had that POS for about 6 years now). Of course, I'm getting a "man's" automatic in a TH400

 

yeah, yeah, i know, 700s got a bad rep when they first hit the road in the early 80s, but for you to kill a few of them behind a 2.8 is pretty odd. either whoever built it has no frickin clue, or you have other issues (cooler, linkage, improper throttle pressure,.....)

i for one am putting one in my 45 wagon and in my wife's fj60.
i have 3 close friends that run these transmissions behind 350 tbi motors and they have not had any problems, even after 40k plus miles.

no the matter is the 700 is a combination of a bad idea and a pice of shit


my old man is on his 5ft yes no 5, 700. factory 350 TBI 89 3/4 van

yes he does have a led foot but no excuse

the van he had before that was a 86 3/4 ton with a 350 with the 400 and he abused that just as bad and it still has it factory tranny and its fine (my bro drives it now)