Turbo 250 or 350
 

In the process of building a 68 chevelle 396/325 for G/SA. My first question is how much quicker is a metric 200 than a light weight turbo 350. Has anyone kept records on 8 inch torque converter weights minus fluids? Is there anyone out there that has raced this combination or has been next to one of these cars and can recall 60 ft times, any information would be helpful, thanks Mark

Re: Turbo 250 or 350
 

A 250 is the same basic transmission as a 350, except the 250 uses a band for second gear, instead of clutches and a sprag. I don't think the second gear band in a 250 will hold. And besides, it wouldn't be any quicker.

Are you sure you don't want to compare a 200 Metric to a 350?

Re: Turbo 250 or 350
 

Thanks for the correction, the metric 200 is the trans I was thinking about. The thread has been edited.

Re: Turbo 250 or 350
 

This is just a "FWIT" answer. I really thought I wanted a Metric 200 for my project. There are a lot them in stockers now.

Someone might sway my opinion on this but, from talking with a couple different racers, they may not be as great as they seem. They have been described to me as being "fragile". As in requiring the transmission to need to be freshend between 50-150 passes. Here again, take it as a comment, I'm passing along second hand information.

I'm going with the t-350 on my crate motor project. Down the road, once I get the car running and established. I may look at a metric-200 again.

Re: Turbo 250 or 350
 

If you want to run a 200, there are only a few people who build them well enough. Two of them I am familiar with are Scott McClay and Thomas Arnett. There are others, but those two guys build a 200 that will hold up to MOST Stock Eliminator cars. And yes, they are a little faster than a 350, even a really light 350.

Re: Turbo 250 or 350
 

It is my understanding that a 350 has almost the same external dimensions as the Glide, uses 15-17 more HP just to turn the transmission than a Glide and a 350 weighs a little bit more than a glide(maybe 15-20 pounds) and you cannot use a 350 with an engine that revs over like 7000 rpm( they want to self destruct). BUT you do get that extra gear in there!!!
Now a Metric 200 has the lite weight of a Glide, you can spin the engine well over 7000 RPM like a glide , it takes about the same amount of HP to turn the trans as a Glide AND you get the benefit of the extra gear. Its weak point is UNLESS it is really beefed up it will self destruct on its own at low RPM , in a heavy vehicle, in normal everyday street use that's why GM stopped using them.
Unless you are looking to extract the last thousandth out of your car--you do not either want the hassle of the maintainence or have the ability to do trans work you might be better to go with a 350 til you hit that plateau in your level of performance where you feel you could use the extra gear that both transmissions over---Comp 387

Re: Turbo 250 or 350
 

We routinely hit 7800-8200 with a TuboAction T-350, and have not had any problems in 8+ years of using them. We do however freshen them up every 200-300 runs.

Re: Turbo 250 or 350
 

Bill---every one has their success story---yours is one of them---I'm by no means any kind of an expert on 200 vs 350 transmissions---Only that not very many if any of the Comp guys are using a 350----lotsa proflites /glides and some 200 but only ony guy I know of is/has been using a 350 and he is doing the R&D as a test vehicle for a racing trans company we all know---Comp 387

Re: Turbo 250 or 350
 

I have been very pleased with my TurboAction 200. Paul, in my opinion, is the man for those !

Re: Turbo 250 or 350
 

Nope, a 350 will not explode at RPM in excess of 7000. I've built them since 1984, and never seen one explode, and that includes a lot of race transmissions.

Nothing explodes like a TorqueFlite!!!!!!!

Re: Turbo 250 or 350
 

Didn't Keith Lynch Run A Metric 200 or 250 something behind his 375 -- 396 B/SA with a steady diet of Royal Purple and it worked like a swiss watch? I think that it might have been a Scott McClay piece.

Re: Turbo 250 or 350
 

350 with 250 shafts and drums, lightens them up almost 10 pounds, cut some off thepump so its a little less volume, cheap and effective. Told it can be worth over 10hp at the wheels with a small block, but haven't yet tested it myself. Don't worry about rpm.

Re: Turbo 250 or 350
 

A coupla things--- I am NOT A TRANS EXPERT----Only telling you what I have observed/heard in the pits!!!! Guys like Keith Lynch I will bet do lotsa maintainence on their cars and they have these cars apart and back together monitering their equiptment and doing preventative work to keep them in tip top shape---

If you ever saw the inside of a McClay 200 compared to a stock trans you would understand why he gets as much as he does for a trans!!!! Lotsa hand made or reworked beefed up parts in them very little stock stuff---

Some racers put a trans in and run it for a whole season or 2 and never even change the fluid or filters while others have em apart every so many runs--- whatever works BEST with/for your combo is what you should run--Don't be afraid to experiment!!--Look around you and see what a racer with a combo like yours is using ,ask lots of questions ,talk to the really reputable trans/convertor guys most will point you in the right direction while some will tell you anything to sell you something. Nobody is gonna give you their deep dark secrets but many will help you get close in performance.

Re: Turbo 250 or 350
 

The 250 forward input drum is a lock up drum, and is the same as a 350 forward input drum. The 250 direct drum has no sprag, you cannot use it in a 350 or you will not have 2nd gear.

The output shaft from a 250 is "gun drilled" and slightly lighter. The sun gear shell from a 250 is "swiss cheesed" and slightly lighter. Combine them with an ATI aluminum forward input drum and an ATI aluminum direct drum and you have a light 350.

Re: Turbo 250 or 350
 

These are probably some of the best words I've heard. This has turned into an interesting thread. What it will do for me? Lead me to do more investigation. For those of us, yet to make it to the track. Discussions like these yield a lot of information to help with future decisions.

Still going with a T-350 to start with.

Re: Turbo 250 or 350
 

Robert, the box I described runs in the 427/425 Camaro in A or AA for two years and hundreds of passes. Looks as good when it comes out as it does going in. I freshen it purely out of guilt.

Re: Turbo 250 or 350
 

I've run a Coan 350 for a little over a season now. Although I had to redo a few things in it after 70 runs tore down and everything looks good. Of course I have no real power but do give it some RPM shift @ 9800, near 10.000 at the stripe. So I'd say RPM is not an issue. Good luck with what ever you chose. Joe

Re: Turbo 250 or 350
 

How much quicker in a car like mine? Any 8 inch converter weights? Thanks

Re: Turbo 250 or 350
 

The only downside to a T350 (besides the rotating mass) is whenever first gear is under power, second gear is turning the incorrect direction (ie in reverse). Therefore when the 1-2 shift is made second gear must stop rotating and reverse direction (to the forward direction). A secondary impact to this is when in first gear over a certian RPM (6XXX +, each one is different) the second gear clutches will start to drag, and when they are rotating in the opposite direction it has a tendancy to kill ET.

With all that being said, the reverse rotation, the stop, and the sudden forward acceleration of second gear could have negative consequences to the durability of a T350 trans it is consistantly over-reved. However most racers I know use 1st gear only to get the car moving and shift to 2nd very early.

It has also been our experience that shifting 1-2 early does not negatively affect ET to the same extend shifting late does.

I hope I got that all right.

Re: Turbo 250 or 350
 

Does the metric 200 function different? Any 8 inch converter weights?

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.

Re: Turbo 250 or 350
 

I would like to learn what different 8 inch converters are weighing out there dry, can anyone help?