Switch-Pitch torque convertors

[ChevLoRay]

I had a '67 Skylark that had a 340/2-speed automatic, with a Vari-Pitch torque convertor. The full-size Buicks had Vari-Pitch convertor on the TH400's. Kenne-Bell used to do a lot with them, 20+ years ago. I haven't looked in a while to see if they're still in business.

Anyway, my question: Have any of you ever run a "switch pitch" convertor behind your truck engine? I like the variable pitches that they have, which can increase torque multiplication from a standard 2.1 to a factor of 2.5. What I'd also like is a lock-up feature for better mileage. I'd really like to stay with my TH400, instead of going to a 700R4. But, that may be the best thing to do.

[mooneyes]

.....Darrell Young Racing Transmissions in California makes them..never had one but always thought it would kick a$$...

[paintpyro]

What exactly are the benefits of a vari-pitch converter? How does it work?

[FRENCHBLUE72]

Kenne-bell is still in business I would also like to know what a switch pitch converter is??

[ChevLoRay]

I was actually reading a November, '66 Hot Rod magazine, and it was going over the changes for the new '67 models.

The Buicks used them in the Skylark and full-size models. Those convertors have a switch which causes the vanes to move, slightly, changing the pitch of the vanes. The standard pitch offered a torque multiplication value of approximately 2.1. When the pitch was switched, the torque multiplication factor changed to a 2.5. The increased factor, increased the torque available for initial acceleration. The switch would only happen when vehicle speed was below about 5mph.

Bottom line, those convertors gave you more torque on the bottom end, for take off.

I'll find the website for Kenne Bell, and see what they offer.

[onelow69]

I had a th400 switch pitch trans from Darrell Young Racing Transmissions a few years ago it worked great, did not know if anyone knew him or not, anyway, you could have a little more than normal stall (say 1500rpm) for the street and flip a switch when you wanted a higher stall (say 3000rpm) for drag racing or for just smoking the tires off. Its really for getting better fuel mileage, trying to have best of both words. Thats why I went to a 700r4, it basically the same thing with a lockup converter and overdrive.

[jimfulco]

http://www.paeenterprises.com/performancetips.html
www.buickperformance.com/switchpitch.htm

[slam33]

I haven't seen Darrell for about 10 yrs now, but we were buds back in the day. He use to buy parts from me when I was in the parts biz. He build most of my trannys too. He did one for a 79 Caddy the we had dropped a 540 BB into, never could blow the trans but we did snap the snout off the billit crank the was in it, that one cost us about 15g's to fix. I'm going to have to just go look him up sometime soon. When I saw him last he had this tiny little shop in North Hollywood on Burbank Blvd, that was a long time ago.

[onelow69]

When I was living in LA Darrell Young moved from that shop in North Hollywood to Tujunga to an even smaller shop. He built my 700R4 for my 62 Nova and did a nice job on the trany. It took about 3 month to get it but was well worth it. I even saw his 66 Nova that he use to race and test his tranys in. Man was that Nova fast. Good times.

[68racer]

I run a switch-pitch in my '68. I bought it from PAE. I have a ZZ3 small block in a 13 second truck. Gas is very expensive here, $6 a gallon. I could never get better than 15 mpg with a normal TH400 and 11" converter. I can get 20 mpg with care now.

The s/p put about 1mph on the trap speed. Launch and 60 foot is about the same even though I can pull higher revs on the line, about 2000rpm. I have the 12" 4000 stall converter.

PAE recommend CAT 30 weight transmission oil and I would agree with them. The high stall will generate a lot of heat.

I am fitting a 502/502 next year and I think this will work better with the trans, I don't think the small block has enough torque.

I designed a system that turns off the high stall when you hit a pre-set rpm, if anyone wants details let me know.

It is a lot nicer to drive on the street than a normal trans with a high stall converter. There is always increased slippage with a high stall 'verter and this is unpleasant on a drive.

Now if anyone has a gear vendors for sale cheap....

[Stroker]

I'de like to know the details of your setup. That would be the ticket wouldn't it. Gearvendor OD, Turbo 400 with a variable pitch converter. I know where there's a broken GV OD laying in the corner of a shop, I better see if I can buy it and get it repaired. Are there any draw backs to this type of converter besides price? What is the price range for one? Thanks....Stroker

[68racer]

To switch the converter to low stall at a pre-set rpm I used a relay to activate the internal solenoid. The solenoid turns the stator to high stall indirectly, if it is off you are in low stall.

I wired the control positive side of the relay with an on/off switch to give me manual control. I only turn it on at the track. The earth side of the control circuit is wired to the grey wire on a MSD rpm switch. This is disconnected when you reach the rpm selected. This breaks the control circuit and so the slave circuit in the relay which deactivates the solenoid, and turns the converter to low stall.

I consider this system simpler, and more consistent than using a timer.

I have heard that they won't take extreme levels of horsepower, but you can break anything if you try hard enough. They are not the 'best thing since sliced bread' that they are often sold as. To me the biggest improvement has been the normal road manners. It is like driving with a stock converter. If you are going full race I wouldn't bother with the extra complexity. But as I run street/strip it makes it more civilised. The high stall is not as obvious as you might imagine, lets see what the 502 does to it.

I think the whole box and converter cost $1000, no core. Check PAE for current pricing.

I beleive the Gear Vendors are manufactured by GKN in the UK. But I would have to buy one from the US, very annoying.

[GSXMEN]

One of the best quality switch pitch converters is sold by Tri Shield Performance. The owner (Jim Weise) is also the founder of www.V8buick.com - you can also find Jim Burek, owner of PAE Ent. over on that board.

You can find the SP 400's in stock '65-'67 Buicks (also Caddy's, Olds & Pontiacs). No idea why Chevy didn't hop on board with that idea.

The switch pitch setup is pretty slick!! You can drive around at a low stall (1800 or so)....when you want it or when you get on it - you'll stall to the high side (3000 or so). Just depends on how you set it up. You can have the solenoid hooked up on the manifold to trigger it automatically. You could also use a toggle switch.

You can spot them at the junk yard too. The electric hookup on the side has 2 terminals, instead of the usual one. Best to look at the www.Buickperformance.com site to get all the specifics on what to look for.

[veedublu]

I had one of these SP TH400's built to run behind a 500ci Cadillac engine, but still haven't gotten around to installing it.

The trickest way I've heard to use them is to hook them to your brake light switch and also use a manual switch. This way you will leave a stoplight under high stall and it will tighten up automatically. Or, it has been suggested these are great to use with a big cam, so the lopey idle has a "loose" converter when sitting at a stoplight.

I could be persuaded to sell mine if anybody is looking for one... performance build for street/strip use.

John