Technical Yoke to yoke installation

Let me begin by letting it be known that I am no where near the smartest guy in the room.
Having said that, let's begin.
I am in the planning stages of a copy of a 100" early gas dragster.
Model A front end, K88 style chassis, SBC, etc.,etc.
I was given a 55 Chevy 3 speed transmission that would fit the build just fine. It has the typical long tailshaft.
I'm laying out dimensions on the shop floor, and it occurs to me, "in order to get the engine back as far as I can, and still have some leg room in the cage, why can't I butt the yoke from the rear of the transmission to the yoke on the rear end and run a single U-joint?"
Most here would go out and find a shortie transmission from a truck, and have a very short driveshaft.
The rear is bolted solidly to the chassis, the engine and transmission are both bolted solidly to the chassis with a motor plate and a cradle in the front. The crank, the mainshaft of the trans, and the pinion shaft are all in line. Nothing moves.
Would that work? My logic doesn't see a problem here, am I missing something?
In the late 60's, I crewed on a Top Fueler that had a coupler between the clutch can and the rear end, what would be the difference?
Don't want to start some great pissing match here, I'm quite OK with "no, dumbass, it won't work".
But if not, I'd like to be schooled as to why it won't work.
Thanks, Mike..........

 

I would think chassis flex between the transmission and rear end would be the problem, the rest of it is bolted solidly together.

 

Are you proposing no drive shaft? HRP

 

Those 55 transmissions are not that strong and you had better have some spare tranny's before you go to all that work setting it up. We used to run a truck 3 speed using second and high in a Model A , but it had a short drive shaft. About a foot long with solid rear suspension.
I have seen a single u-joint setup like you are talking about back in the 60's. I would go with a coupler if possible, but it's your jewels in the car not mine. If you decide to use it make sure you have it incased in a steel shield.

 

BACK IN THE 60S I HAD A FRONT MOTOR DRAGSTER WITH A FORD 427 CU FE MOTOR AND A 55 FORD TRUCK SHORT TRANS ...USED A FRONT YOKE OF A DRIVE SHAFT AND U JOINT ON THE REAR END ....NEVER HAD ANY PROBLEMS.....JUST BUILD A SHEALD AROUND THE U JOINT....JUST IN CASE ...THINGS HAPPEN...

 

Yes, that is what he is proposing.

 

Yes I was proposing just a single U-joint, yoke to yoke. If this isn't reasonable, how short a driveshaft can I get away with?
The car is going to be a show/cackle car. I have absolutely no intention of ever putting this car on a track ! Repeat, no way I would ever go fast in a mild steel car I welded together! Mainrails of 2X3 3/16, tapered to 1 3/4 in the front, like a model A mainrail. Cage tube of 1 3/4 .095 seamless. Soft SBC, probably 2 AFB's.
Having said that, I still don't want some geezer like me looking in the car and spending the rest of the afternoon telling everyone around him why it's all wrong. And, yes, it would be rather naive to build this and not put in blast shields.
I plan to find a pressed steel Lakewood style scattershield for my clutch can, and build shields for the transmission hook-up, and for the rear as well.
I am not married to this idea of the single u-joint. I was just trying to think out of the box. Thanks, Mike

 

Cackle car . you should be fine with that setup. I thought you were going to race it.

 

No, I believe in the reasoning behind the 6 point cages and most of the other safety rules the No Hot Rods Anymore has come up with. There was a lot of carnage in the dragster ranks in the 60's and 70's.
I've been looking for decades for a little FED to restore, and haven't found one. So...I'm going to build my own. Just to take around to parking lot shows, GoodGuys, things like that.
The main reason it will be a runner is so I can get it off and on the trailer.

 

The drag race people these days use a splined coupler, should be easy to find used ones.. The reasoning is they are not as rigid as a u joint will be. Now here is what we did on the tractor pull units we built . We put a chain sprocket on the trans and another on the rear end . Tie them together with a double roller chain, and yes they took a lot of horse power without failing . The chain actually allows a small amount of movement and mis alignment.

 

The last cackle I saw they explained to the crowd that there was no coupler of any kind between the engine and transmission for the safety of the crowd. That way they could rev them and not have one accidentally move into the observers.

Really need it connected at all? Most push them into place.

SPark

 

Mike,Why not give Don Ross out in Garland a call...He is dong that kind of stuff all day long..
214-327-7312 is his phone....

 

Bob, I already have Don involved with this project. I'm sure he will have an opinion on this!

 

My little 120 inch wheelbase FED I ran in the late 70's/early 80's, was setup just this way, with a "shorty" aluminum Powerglide (aftermarket shorty kit), connected directly to the 57 Pontiac rear end with a shortened slip yoke and U-joint. Rules required a shield around the U-joint/coupler/driveshaft IN the driver's compartment. This was an old Kent Fuller chassis of larger diameter, mild steel; the only real flex was from the motor-plate forward. Never had a problem with the setup. In the pits and staging lanes, spectator types would always comment on how the driver sat, and the family jewels, in a FED. My RED did have a short driveshaft (nine inches C/C on the U-joints), but I've seen RED's setup the same way with just a coupler/U-joint. In the earlier years, the old Muncie 318 transmission was used with a "shorty" kit (probably home made in most cases, but there were aftermarket ones available), and only used second and third gear; first and reverse were completely deleted. Where you'd find one of those shorty kits now would be the problem. You might find the shorter version of the Muncie 318 transmission will work; those were found in 58-64 X-frame Chevrolet cars, and some trucks. The trans-mount is virtually at the very end of the output shaft/extension housing on those transmissions, and would give you about 6 inches less length/more room when compared to the "full length" Muncie 318 transmissions. I used to have a Gibson Model "D" garden tractor, made from 1946 to 1958 (company was sold to others in 1953). They used a 1940-ish Chevrolet 3 speed transmission with a topshift and were directly coupled to the 8 3/4 inch MOPAR rear ends they used (narrowed and with manual brakes) using only a U-joint. Course they also only had a 9 HP, single cylinder, Wisconsin engine; they were still a 3 speed plus reverse, and used the Gibson Companies shorty kit. Those tractors used "tiller" steering setup; they did't have a steering box, though it was an option, and "fancier" models had a steering box). So, what you propose will work; it's been done that way for a long time. I am Butch/56sedandelivery.

 

Thanks Butch!! I thought it would work, especially since I don't plan to flog the set up, only to use it to get off and on the trailer.
I'm seriously thinking of incorporating the length of the standard tailshaft in the dimensional drawing of my chassis so that I will have more room in the driver's compartment. It will mean that the engine will be out maybe 6 more inches, but that might help this 69 year old, 6 foot, 200+ pound fool get in and out !!
I'm collecting parts right now. I just picked up a model A front end to use, and when I find a pressed steel scattershield I will lay block, scattershield,transmission and rear end out on the floor of the shop.
That way I can pencil in the last of the dimensions on my working chassis drawings.
I'm betting that it will work well without the "shorty" transmission. Thanks, Mike

 

Mike, the only issue I see with this is a lot of Cackle events require the coupler to be disconnected to fire the car. (I think it's a insurance thing). A lot of guys are building a little in and out type box that allows them slide the coupler sleeve off without having to disassemble anything.

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A typical connection between the torque converter output shaft and the transmission input shaft on a bulldozer (yes, the trans and converter are separate components) is a double U-joint arrangement with about a 1" coupler between them. Some of these dozers are running >600 hp and well >1000 lb-ft torque.

 

BlownFuel,
The car will have a 3-speed transmission from a 55 Chevy car with a modified vintage Fenton shifter on it.
The transmission can be set in neutral before the engine is started.
This is not a high-gear only car.
I have seriously entertained using a shorty Powerglide as the Powerglide transmission showed up as early as 55. But I don't think anyone was using them in drag racing before the late 60's, early 70's. That is why I'm staying with the early Chevy 3-speed, it was in common use in some of these lower class gas dragsters around the 61-66 period I'm shooting for.

 

I ran my altered with a setup as you talked about with no problems. Used a good quality racing joint and u bolt kit from Lakewood, ran 0 degree pinion angle, had a 360 degree shield around the joint. The engine, trans, and rear were mounted solid.

 

Thanks, Speedy! I thought that would work! And the fact that the car won't be raced makes it even more probable that I can do this.

 

Sure you can do it Mike. Just about every car that we built back in the 60's was set up that way and we never had any problems. You are also correct in that as long as the trans has a neutral you don't need the drive line disconnect required for the direct drive cars.

Roo