Re: Turbo 250 or 350
 

I've had very good luck with 350's for a long time. I have 3 cars with sister transmissions...tci sprag (the $60 one) and a TCI forward manual VB everything else stock. Good coolers as well. RPM has never been an issue. 2 of them get beat up on the street real bad...over 7000 RPM shifts and my crate car sees 7000+ in all gears and at the stripe. My other street car runs 9.60's on nitrous and the trans has been in the car for 8 years with no freshen. That see's 8500 to 9000 rpm (377 sbc) every gear change. Does anyone know if a 350th converter will work in a 200 Metric?

Re: Turbo 250 or 350
 

I believe the converters are different between the 200 and 350 but I think you can set the 200 up to run the turbo converter.

Re: Turbo 250 or 350
 

Bill, you are pretty close. The second gear clutches and steels are in the case. The outer race of the second gear sprag is what they engage. The second gear sprag is mounted to the direct drum. Shifting to second gear stops the direct drum, as a sprag is a one way clutch, it holds in one rotation direction, and slips in the other. When shifting to high gear, the second gear clutches release, the direct clutches apply, and the direct drum accelerates instantly to match the speed of the forward input drum, which is turning at or near the engine RPM, depending upon the slippage factor in the converter at the time. When in a forward gear, the forward input drum clutches are always on, and the forward input drum approximately matches RPM with the engine, again depending on slippage. You may or may not have the low gear clutches applied, depending on whether or not you leave in manual low gear. If you have any sort of auto 1-2 shift, in a 3 speed automatic, most of them do not use the low gear clutches, but rather they leave on the low/forward sprag.

Any time you accelerate a component from a stop to a relatively high RPM, the heavier the component, the more power is required to accelerate that component. That power is used to accelerate that component rather than to accelerate the car.

A sprag is a liability. Any time you use a sprag on an upshift, you run the risk of "rolling" that sprag, so a bigger, stronger, and therefore heavier sprag is required. A 350 or a 400 that is operating close to the way they were designed to will be using a sprag on the 1-2 shift. In order to make a 350 live, it is necessary to use the heavy duty 2nd gear sprag from a 400.

There are basically two ways commonly used to stop a drum. Either a sprag mounted to the drum and external clutches (as found in a 350 or a 400 in second gear) or a band on the outside of that drum, as is found in most other 3 speed transmissions. A TorqueFlite uses a band, as does a C4 or a C6, and the 200 Metric. When using a band, you have the torque capacity of the band itself, and the servo you apply that band with, so to increase the torque capacity you may increase the band area or the friction coefficient of the band itself, you may also increase the line pressure, the size of the servo, or both.

Using lightened components does two things. It lessens the load on what ever is being used to accelerate or decelerate that component, and it lessens the power absorbed trying to accelerate that component, allowing more power to be used to accelerate the car.

I hope this answers the questions that were asked. And there was no intent to belittle anyone's knowledge on the subject.

Re: Turbo 250 or 350
 

A 350 (as well as a 400) uses a different pump drive hub, a different stator shaft spline, and a different input shaft spline from the 200 Metric. Some of the 200 builders modify the pump and forward input drum in the 200 to match the 350. If I were buying a 200, I would certainly want it done that way.

Re: Turbo 250 or 350
 

Let me add: The main difference is total stack up height of the 200/2004R/700R4 converter, which is about .300 shorter than a a 350/400.
The stator shaft spline is actually the same on all of them,..even the 125/440 FWD trans.

Now ,seeing I don't build transmissions for a living ,I'll assume I can post this here.

200 durability issues:

When we built the trans for Tibor's L/SA Firebird (which is now for sale),we decided to go with the 200, already having done the research on my Omega.
I built the first one , using a Turbo Action valve body and a Sonnax billet servo, and no lightened or heavy duty stuff. That trans was in the car all of 2006 when Tibor won enough rounds to tie for first place in the world points.
After that season, I did an inspection and found the factory writing still on the direct clutch frictions. The factory replacement narrow band was still like new also.
I built a second trans for a spare for the 07 All Star race. That unit now has a Leo (REMAC ) 2.91 low gear planetary and a wide Kevlar band ,just for insurance.
All in all ,we've had great dependability with both units. One of them started to roll a low sprag one time, but we caught it in time.
The Firebird is now in the 11.70 range @ 3600 lbs ,and still no problems.

Just some real world experience. No conjecture here. Carry on...

Re: Turbo 250 or 350
 

Mark, you are indeed correct on the stator spline, I checked my notes, and was going to correct my post, but you beat me to it.

Re: Turbo 250 or 350
 

seems like alot of BS to build one of these trans. Probably easier to just buy one. I can imagine alot of machine work to make things fit....not that hard when u have the machines at your finger tips...but when your boss is watching its tough to say your making parts for the tow motor...HAHAHA

Re: Turbo 250 or 350
 

It's not the trannys that require the machine work. It's just the retrofit 350 converters.
I just build myself a straight 200 converter (can I say that here?)

Re: Turbo 250 or 350
 

Thanks Alan and Mark, I will probably screw it up again when I try to pass the info on. Still I try to learn when I can.

Re: Turbo 250 or 350
 

Bill, it's an easy mistake to make, and you got real close anyway. Everyone is entitled to a few mistakes. You do a great job of helping other racers. We're ALL trying to learn. Especially me.