Thread: Driveline alignment: how?

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Hello everyone. This is my first post, but I am hoping someone here can help me as I figure alot of hotrods put motors/trannys into cars that were never supposed to have them.

I have a tranny/engine in a car that was never ment to have it. However, the thing vibrates on the hwy, and I have narrowed it to the driveline alignment. What I am wondering is, how do you guys go about aligning the drivelines on your custom hotrods?

I have read other places that the total out of perfection should not be more than 2*. (1* off at tranny, 1* off at rear end) for it to be correct.

I just cannot come up with a way to do it.

Please help

-Bryan

you can adjust your angle via the transmission cross member,
( not too radical though),,if you can attache a plumb line or string to align with your oil pan,,and bring it back along the oil pan,,then to your transmission,,to rear end,,,you will get a good indication of your angles.
Your driveshaft may be out of ballance, causing the vibration.
Simple things like universal joint wear will also give you vibration,,,especialy if your angles are wrong.
Need more info on your rear axle setup to be further help.

Its an IRS setup. I also have a custom aluminum driveshaft. I have that out in the car and plan to drop it off this week to make sure its balanced. (I suspect it is not, but the vibration is so bad I didnt like going faster than 80mph on the hwy...) The driveline was also deffinatly not within the 2* I mentioned. It was very visible. when i got the car up and running last spring I didnt know anything about driveline alignment. I thought thats what the u-joints were for, so it was pretty far off. Probably a good 10-15*.

I figure alot of it will be gone just eyeing it better, but since I am down there and making new mounts anyway I'd like to get it perfect.

edit: the problem I'm running into, is how do I align the diff nose when there are no flat surfaces on it? Especially within 1* of the tranny tail, which is a very precise measurement...

Not too confusing....
Universal joints need to cancel each other out, as far as trans yoke to shaft angle in front and shaft to pinion yoke angle in back.
You need to have some misalignment in the driveshaft and cancel it out at the diff in order to get the u-joint trunion rollers to roll. If the trans/shaft/pinion were all perfectly aligned, then the rollers in the u-joint would not oscillate (roll) and the rollers will 'brinnel' into the trunion and cap and your u-joints will wear out prematurely.
So, that being said, measure your trans yoke to driveshaft angle.
Say, for example, it is 2 degree's down.
OK, then make your pinion 2 degree's up.
Whatever you have in front, you try to cancel out in back.
Drag guys put the pinion down a couple degree's extra to counteract spring wrap that raises the pinion on accelleration, but for street cars, shoot for zero.
Remember that the engine is not perfectly aligned right to left in a lot of cars either (steering box clearance, or weight bias)...
Good question.
Hope the info helps.
Jeff

Originally posted by crash41301
Hello everyone. This is my first post, but I am hoping someone here can help me as I figure alot of hotrods put motors/trannys into cars that were never supposed to have them.

I have a tranny/engine in a car that was never ment to have it. However, the thing vibrates on the hwy, and I have narrowed it to the driveline alignment. What I am wondering is, how do you guys go about aligning the drivelines on your custom hotrods?

I have read other places that the total out of perfection should not be more than 2*. (1* off at tranny, 1* off at rear end) for it to be correct.

I just cannot come up with a way to do it.

Please help

-Bryan

http://www.drivetrain.com/driveline_angle_problem.html

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