Tailshaft position.

[Guest 305240]

Ok, I got the engine and trans setting in there sweet. I'm using the 240 trans mount. I just have to drill 2 holes in the mount. The engine is perfectly centered going by the steering rack. The tailshaft is centered also. By holding a broom handle up against the tranny output shaft, (I cut it off with a miter saw so I know it's square)The other end is almost dead center of the pinion nut. I'm running the R180 for right now, but plan on putting the R200 in soon. My question is, before I start drilling, should I move everything to the right so It will line up with the R200? Me eyesite isn't that great, so I'm using a lazer level also.

[wheelman]

You don't necessarily want the tail shaft point directly at the diff input flange. What you're interested in is making sure the angles of the diff input flange and trans output shaft are within 3 degrees total of each other. The way to measure them in the vertical plane is using an angle finder, I made one from a protractor. What this means is that you want the same angle on the end of the tail shaft that you have on the diff flange. Example: The original Datsun tranny tail shaft was lower than the front of the tranny, it pointed down at the back. The front of the diff points up at approximately the same angle. You want the same type of situation with your new install when you're finished with it. It might mean that you'll need to raise or lower either the tail of the tranny or the back of the diff to get the angles correct. As far as side to side, I don't know how to measure those and think that if you get the vertical component very close the total angle should be within tolerances.

 

I hope this makes sense if not do a search about drive shaft angles and you'll find alot of information.

 

Wheelman

[Guest 305240]

Thanks again wheelman. I've read those driveshaft threads a zillion times. Nothing seemed to click until you said it. It all makes sense now. Tomorrow the trans mount gets drilled and the tailshaft gets bolted down. Then I can finish mocking up my mounts. I'm using the stock mounts with the single bolt going down. I was going to use the Ansil type mounts, but seeing as I already had these, I decided to use them. The motor mounts seem pretty easy to fab. I'm taking some more pics tomorrow. Thanks again.

[blueovalz]

This also (and I'm sure you've realized this) goes for the horizontal plane as well. I found that with the tailshaft centered in the tunnel (or a centered engine), I was just at the recommended limit on U-joint angle due to the fact that the pinion on the differential is shifted sideways within the tunnel due to the design of the case (otherwise, the half-shafts would be of differing length if the pinion was centered in the tunnel). Parallel centerlines (in both planes if you wish to look at it as two separate planes) are the important thing here. I did not realized the pinion was shifted toward the passenger side until I had the engine/tranny combo set permanently, and now wish I'd shifted it toward the passenger side as well to reduce the U-joint angle displacement. Normally an inch or so displacement is no big deal, but with a short driveshaft as the Z uses, this small amount of displacement becomes important.

[buZy]

I just finished doing the same thing to my car last week. Yes the vertical plane is easier make parallel. A digital inclinometer works great.

In the horizonal plane the rear end pinion is shifted to the passenger side. The closest I could get to perfect parallel due to header clearance I was .43 degree off (less than a half of degree) with the tail shaft pointing to the passenger side. I measured the horizontal plane as follows. 2 plumb bobs on strings. (home depot) One hanging from the crankshaft centerline on front of the motor and one hanging from the trans tailshaft centerline. Then markering the touch off points on the floor I used a lazer level to strike a visable line I could now measure. Three areas of basic measurements. The first crankshaft centerline front of motor between the frame rails. This told me the engine was basically centered left to right in the car. it was within an 1/8 inch The next one was at the rear most part of the car. For example I used the bumper mounting holes, measured between the two, divided in half to find the center of the car itself. With this point now marked on the floor I could see the lazer pointing over to the passenger side an inch or two at the back of the car. Made a mark on the floor showing this point too. Trig these three points and you can find your angle difference. I used a computer drafting program to do the math. After that it was just a matter of moving the tailshaft of the trans more towards the driverside the best I could.

Keep in mind there are many different ways to "tweak" these angles. Some might even tell you its an art. I dont know. But I do know that some favor a pinion nose down from parallel to compensate for the pinion rasing under power. I didnt get that luxury being I could get my horizontal plane perfect. So in the same way I tweaked it just as if I lowered the pinion nose down. The driveshaft doesn't know the difference in theroy. In reality I tested finally it with no half shafts in the car, just the r200 and the drviveshaft. I did this to just study the driveshaft vibs alone. IT WORKED!!!!!! The car on level jacks I had the T-56 in 6 gear at like 5000 engine rpms. thats pretty fast.... and it was smooooooooth. It was really (way) bad before. I should mention my driveshaft angle ended up to be no more 1.8 degrees. Yup short driveshafts dont like large driveline angles. This was the hardest part of the whole job getting this low driveshaft angle number. Much fabrication and design was spent lowering and remounting the pinion nose.

[Guest 305240]

Thanks for all the input and advice guys. I don't take any info help and just chuck it. I've put it all in it's own folder for reference. It helps this old tired mind. I don't have any of those fancy programs or degree things. What I do have is a lazer level. I mounted it to the end of the trans yoke and sptted the red dot 1/4" high and 1/2" to the right (drivers side) of the center of the pinion nut. (looking at the diff from the front to back. I spun the trans yoke and the red dot stayed where it was. I think I'm pretty close. any thoughts?

 

The car is setting level on blocks. I shimmed the blocks to get it level both ways. I checked it with the frame rails, steering rack as well as the cross member. The carb sets level side to side and front to back. I'd say it's pretty good. These leveling checks were made with the engine setting on the fabbed mounts. no jack under to support anythinig. What makes it easier for me is the front nose of the unibody has been cut off just in front of the sway bar. I have an 280 nose I'm grafting in as soon as I get the engine bay painted and detailed.

[buZy]

You dont need computers or expensive measuring tools at all.

In the horizonal plane, (top view of car), you could just use a tape measure and center the trans tailshaft and the front most engine crankshaft pullley in the car. Go off your frame rails. Typically matching the numbers driver and passenger side. (Example, 9 inches trans tail shaft drivers side, 9 inches front engine pulley drivers side.

8 7/8 inches trans tail shaft passenger side, 8 7/8 inches front engine pulley passenger side. Motor might not be 'perfectly' centered in car and it doesnt have to be. Just parallel. This should get you pretty close.

 

Vertical plane. (looking at the side of the car.) Get an angle finder at the home depot. The round plastic type with the red needle, magentic base about 10 bucks. Cheap. Check your shim jacks to get the angle finder to read as close as you can to zero degrees on your frame rails. Then raise/lower the trans tail shaft and /or rear end pinion to make them paralllel or the same angle.

For conversation sake lets say after adjusting they both now read 2 degrees with your frame rails at zero degress. Install your driveshaft and now measure this angle. Lets say that number is 5 degrees. That means your actual driveshaft angle is now 3 degrees to the parallel rear end and trans tail shaft. If it comes out to be more than 3 degrees raise/lower/shim the pinion or rear mustache bar to get it to 3 degrees or less. You could also easily shim up/raise your motor mounts if need be.

It might take some screwing around but your roughly 20 inch long driveshaft will run much smoother at high speeds. I hope this helps.