Drive shaft for my 1966 Midget

[mickri]

I have swapped a toyota 3TC engine and 5 speed into my midget. I have to mate the toyota drive shaft to the midget drive shaft. I will have a drive line shop weld everything up and balance the drive shaft. The ID of the toyota drive shaft is 2 7/16" and the OD of the midget drive shaft is 1 3/4." The toyota drive shaft is as long as it can be and the midget drive shaft will get shortened by probably 15" to 18"



I am making a bushing that slips inside the toyota drive shaft and over the midget drive shaft. Here's my problem. I am making the bushing out of some round bar that I had on hand where one end is 1 3/4 OD and other end was 2 1/2 OD. It is held in the lathe with the 1 3/4 end.



If it weren't for this difference in OD's I would bore the bushing to 1 3/4 without taking it out of the chuck. I can't do that in this case.

I believe that I have two options. One is to put the bushing in a 4 jaw chuck dialed in to the OD. Then bore the 1 3/4 hole.

Or start the 1 3/4 hole in my current setup. When I get to around 1 1/2 switch the bushing over to the 4 jaw and dial it in using the center hole.

This is probably one of those 6 of one and half dozen of the other type decisions. I have been going back and forth probably overthinking this. Which would be better or does it even matter since either way I will be dialing in bushing?

 

[Winegrower]

Maybe hold by the big end, turn the little end and as much of the big end as needed, bore the hole and part off the big end...only one setup, concentricity guaranteed?

 

[Tozguy]

Guessing that the bushing will be welded in, what about boring to fit the Midget part, then weld the bushing to the Midget part, mount the Midget driveshaft in the 4 jaw, turn the bushing o.d. to fit the Toyota i.d.
When turning the o.d. of the bushing leave a shoulder to match o.d. of Toyota tube.
Shoulder gives you alignment and something to weld on.

 

[Tozguy]

Some more ideas;
Don't cut the Midget shaft yet. Mount it in the 4 jaw and steady rest. Clean up the o.d. so that the bushing will later slip along easy. Part off at chuck at start of cleaned up section. Leave enough extra shaft for holding later after bushing is installed.
Mount the bushing in 4 jaw and bore to fit the cleaned up Midget shaft. Remove from lathe.
Slide bushing on the Midget shaft to its proper position and weld.
Mount the Midget shaft in the 4 jaw holding by the surplus end and use steady rest at other end.
Turn the bushing to fit inside the Toyota shaft but leave a shoulder. Part off the Midget shaft at or near the bushing.

 

[mickri]

The drive line shop will do all of the welding. And make the decisions on how long each drive shaft will be. I have no experience with this. I am just trying to make the parts for the shop to use.

I have already turned the bushing to the ID of the toyota drive shaft. And I left a lip on the end of the bushing to butt up against the end of the toyota drive shaft. The only thing left to do is bore the hole to fit the midget drive shaft.

The bushing is 1 5/8" long. My current thought is to bore a 1 1/2 hole all the way through the bushing. Then increase the size of the hole to 1 3/4 to a depth of 1 3/8." Then switch to the 4 jaw and dial in the hole to finish off the last 1/4." This will guaranty that for most of the bushing the the OD and ID will be concentric.

That's the plan right now.

 

[Bob Korves]

The drive line shop will do all of the welding. And make the decisions on how long each drive shaft will be.

And they know what they are doing... It is really easy to get it wrong, in many ways. It can look beautiful, but not be straight, and it needs to be pretty much dead on straight and in proper balance or it will vibrate like crazy, which can also hurt the transmission or the rear axle. In my experience, drive line shops do a great job for a relatively small price. Let them do it all , especially with a custom shaft like you need for the Midget. I would just bring them the pieces you have, just like they are, and let them do it right. Anything you do now may well make it more difficult for them to get it right.

 

[mickri]

The shop will have to make the decision on the best way to deal with the different diameters of the midget and toyota driveshafts. I am only making the bushing as one way that the shop could mate the two drive shafts together. It will be their call on whether to use it or not. Or do something else.

I will take them the parts and the car and ask them to build a drive shaft to fit. How they do that is up to them

 

[TonimusMaximus]

I've had a few driveshafts modded. They'll likely just cut the yokes off of both shafts and weld them to a new piece of tubing.

 

[Bob Korves]

I've had a few driveshafts modded. They'll likely just cut the yokes off of both shafts and weld them to a new piece of tubing.

The two cars had different diameter drive shafts, so something custom will probably be required, unless the ends configurations are both available for a single shaft size. If so, that may be what the drive line shop prefers to use, but it would then be a new drive shaft from all new components and possibly or probably a significantly higher price tag.

 

[mickri]

It always amazes me how long it takes me to bore a hole to a precise ID. Followed my plan in a prior post to bore a 1 1/2" hole all the way through followed by increasing the ID to 1 3/4" to a depth of 1 1/2." Took me at least 5 hours to do this. But I have a very tight fit on both drive shafts. Tomorrow I will part off the excess length and finish the last 1/8" to 1 3/4" ID.

Another thing that I intend to make is an adapter that will mate the rear U joint on the toyota to the midget rear axle. And like I have said above I am just going to give this stuff to the drive line shop to use or not use. I have no intention of trying to tell them how to do their job.

I seriously doubt that there is a new rear U joint that would fit the midget rear axle. The bolt spacing on the midget axle is 2 1/8" x 1 3/4." The bolt spacing on the toyota is 78mm. But you never know.