Clutchless Endurance Racing Transmissions

I've been ruminating on this a bit lately. Let's say that you wanted to build a build a budget endurance racecar, and needed it to be clutch-pedal-less. FWD vs RWD layout does not matter for the purposes of this discussion, but figure on putting at least 200whp through it.

First and most preferred are dual-clutch and automated-manual gearboxes. Sporty ones are only available from select 'newer' cars, generally making them more expensive, and/or are generally attached to less than desirable engines for budget endurance racing.

Next and least preferred are standard automatic transmissions. Pretty much any and every thing has one. Most seem to lack both the durability to handle endurance racing abuse, as well as the drivability of a clutched transmission due to the torque converter set to unlock with heavy throttle use. There are a few transmissions from old Volvo's and Mercedes' that I have seen referenced as having been bulletproof when endurance raced, but the most common domestic stuff seems to all be failure prone even with added coolers and whatnot.

The third 'middle ground' option would be a torque converter automatic that can be set (or forced) to fully lock the torque converter any time a standard clutch would be fully engaged. This could be either from the factory or with a tune/switch, and shifted either automatically or manually. Finding some transmissions that can do this would open up more desirable transmission (and engine) options, but information on which ones are capable of this and how to make them do it is extremely scarce.

Considering these options, what do you know about any transmissions that fit these criteria, and which would you go for?

Are manual valve bodies a terrible idea? Because I'm seeing manual valve bodies for a th350 for around $300. Or fully rebuilt transmissions with manual valve body included for ~$1800.

BMW DSG boxes out of 335i and 135i cars are abundant and able to be run standalone so fairly cost effective....

Might ask why you need/want clutchless? 

In reply to STM317 :

There's online guides to make th400s manual valve body for free.  I think one issue is if they allow engine braking.

I don't know much about manual valve bodies, I didn't think they really solved the endurance longevity.

Good to know that the BMW dual clutch units can be run stand alone! That's a good contender, although I'm not sure how I feel about running an N54/N55. I wonder how easily it bolts to older BMW engines.

As to why? Not everybody that wants to race is physically able to use a clutch, not everybody that wants to race is proficient at using a clutch, and the teams slowest drivers have more to gain than the fastest drivers have to lose... Especially if you can take shifting out of the equation entirely. Seems to me that this is a generally unfulfilled niche.

We run Aisin 4-speed autos in two Lemons cars (think A340/AW4) manually shifted using homebuilt paddle shifters. These transmissions use two on/off solenoids to select gears, which allows us to manually shift them with some homebrew electronics. There are quite a few autos that are controlled in this fashion.

We've never bothered hooking up converter lockup. No problems with trans fluid temperature, no trans failures in 10+ races across two cars aside from a front pump seal failure. Both cars are capable of lap times matching those of overall winners in Lemons at our home track (with the right driver).

I will say that in champcar, a car with a torque convertor is 75 points off the overall value.  A car that has at least 1 clutch counts as a manual and you don't get the discount.

Just fyi.

Driven5 said

Not everybody that wants to race is physically able to use a clutch, not everybody that wants to race is proficient at using a clutch, and the teams slowest drivers have more to gain than the fastest drivers have to lose... Especially if you can take shifting out of the equation entirely. Seems to me that this is a generally unfulfilled niche.

That makes total sense and I suspected as much.

There are plenty of autos being abused for hours and hours in Lemons/Chump/LDR and holding up just fine. Aisin A340(or whatever each brand called it), 4R70W, TH350 and a few others I can't recall. We have a Mercedes 722.3 that we nuked with stock power levels and an extra cooler. However I've seen other people have fantastic luck with them for countless hours.

Were it me, I 'd go TH350/TH400 with a manual valve body. Especially if you only want 200hp. They will hold up to that forever.

If you are driving slowly enough that you notice the torque converter, having a solid connection isn't going to make a difference.

Torque converters only "slip" below their stall speed, over that and they are locked up within 1% or so.  Lockup converters exist because the manufacturers want to be able to cruise below the converters' stall speed.

In reply to Pete. (l33t FS) :

And because they aren't designed to be used in situations where the engine is making a lot of torque, the lockup clutches are generally pretty weak.

Edited: Never mind. Rather than taking this thread even further off track for no apparent reason... Even if you happen think that open converters are the best possible option for endurance road racing, that's fine with me. But then at least back that up with additional recommendation that have the reliability and durability needed to excel in endurance road racing, and anything that can be done to help them achieve it.

Driven5 said:

I don't know much about manual valve bodies, I didn't think they really solved the endurance longevity.

Good to know that the BMW dual clutch units can be run stand alone! That's a good contender, although I'm not sure how I feel about running an N54/N55. I wonder how easily it bolts to older BMW engines.

As to why? Not everybody that wants to race is physically able to use a clutch, not everybody that wants to race is proficient at using a clutch, and the teams slowest drivers have more to gain than the fastest drivers have to lose... Especially if you can take shifting out of the equation entirely. Seems to me that this is a generally unfulfilled niche.

I think there was a guy that put one behind a miata engine making serious boost a few years ago. 

Stampie said:

In reply to STM317 :

There's online guides to make th400s manual valve body for free.  I think one issue is if they allow engine braking.

Thanks for that tip.    I used to do it but forgot in the past 30+ years.  So this time I was going to bite the bullet and have it done.   

Tom1200 said:

Might ask why you need/want clutchless? 

Being cheap!  Or at least coming in under the $2000 limit.  I've got a complete 5 speed dog clutch Sienz  sitting on the shelf.  But I don't believe anybody would  believe I traded a Turbo 400 for it.  

In reply to z31maniac :

There is someone on rx7club with a twin turbo LS2 with one.

My only relevant experience is that car development (failure) at the race is way more expensive than the cost of the actual parts.  Whichever way you go, get in as much testing as feasible and bring a spare.  

Pete. (l33t FS) said:

In reply to z31maniac :

There is someone on rx7club with a twin turbo LS2 with one.

Yep, they are pretty stout and there are upgraded clutch discs and clutch baskets for them as well. 

Looks like standalone management of the BMW DCT is pretty expensive, plus the cost of adapting it to other engines, all on top of the transmission itself isn't exactly cheap... Not looking like a very budget friendly solution. Bummer.

Getrag DDCT in a Focus or Fiesta works well in the mountains. 

In reply to Driven5 :

Like I mentioned, we have two different endurance racers with Aisin autos, and no failures, and we have never bothered with lockup.

Cooling is important, we run a stock Volvo in-radiator cooler in one car, and a large external cooler on the other. We also run a large external spin-on oil filter in the pressure line on both cars.

I think our paddle shifting setup greatly helps with longevity and keeping temps down. There's no slipping during shifting since we are directly commanding the solenoids to be on or off, so it shifts hard and is locked into gear. Stock TCUs like to slush in and out of gear for comfort, and that generates heat.

We ran a Chevy t350 Trans in a 78 Malibu behind a beefed up 350 sbc.  Never had a Trans issue.

I know that there is a team from Florida running a Nissan automatic Trans behind the Nissan 5.6 v8 in a larger 4 door Infiniti.  I don't believe they have many (if any at all) Trans issues.  Team infiniti.

In reply to Driven5 :

So prior to racing the F500 I would have never ever consented to racing with a automatic transmission. Having now done several races with it I no longer even notice the fact that I'm running a car with a CVT to be honest.

My point being if you simply put a durable auto-box in the car and run it; everyone would quickly forget about it an drive.

I'd just go with the most sturdy box that fits.  

In reply to Tom1200 :

For that reason, I actually briefly considered whether or not any automotive CVT's might actually be good enough (especially if somehow tunable) to handle it, but I didn't find evidence of anybody having tried it... Let alone with any success.

One of the biggest problems is that preferred engines don't seem to mate with well regarded transmissions, and the preferred (auto-ish) transmissions don't seem to mate with well regarded transmissions. While adapting is always possible, it can also get prohibitively expensive pretty quick. I'll also be trying to figure out what engines makes the most power while still running around the 5GPH fuel consumption range. So I'm hoping by getting a longer list of transmissions, it'll open up the engine options a bit.

I do generally like what I'm seeing about the A340 so far though.