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Does it matter how you put the driveshaft on?


Old 01-17-05, 01:30 PM
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Does it matter how you put the driveshaft on?

Hey guys,

Still working on the restoration project here. The car is VERY close to being able to run. I'm putting on the driveshaft from my 83 donor car tonight, which should totally complete my auto to 5 spd swap. (using parts from an 83 GSL donor on the 85 GS.) I only have one concern. I don't know which way to put the driveshaft on.

Since I am putting on an entirely different driveshaft I have no markings to go by on the differential end of the shaft. Granted, I didn't know that I was supposed to mark the old automatic driveshaft when I removed it anyway. So basically I have this new 5 spd driveshaft that I need to put on my car and I have NO markings to go by. If I put it on wrong is it going to vibrate the crap out of my car? Is there any "wrong" way to put this thing on? I'm guessing that these driveshafts have to be balanced, and that's why they need to go back the same way they come off, right? There is a piece of steel tacked on one side of the shaft, which I'm thinking is there to balance the driveshaft as it rotates.


Thanks guys.

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Old 01-17-05, 01:59 PM
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markings... really? when i dropped my tranny and put a new clutch on i just put the driveshaft back in.. i had no vibrations.. I'm kinda curious now.
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Old 01-17-05, 02:03 PM
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You should mark it when you take it off to ensure you put it back on right, but with a 20 year old car there's no telling if it's been taken off and put back on correctly before.

But, there shouldn't be any vibration from it. If the driveshaft has some counterweights, you might experience some vibration. But since the driveshaft is from another car, if it does have some counterweighting, it probably won't be a good thing since it was balanced for another car.

If you do experience vibration, just try rotating the driveshaft until it stops, or if it doesn't, you now have an extra special characteristic in your car.
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Old 01-17-05, 02:09 PM
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Well, you're right in thinking that the driveshaft should be re-installed the same way that it came out. For this reason, I always take a file and scratch along the yoke on the diff and the driveshaft yoke to ensure that it goes back together the way it was balanced at the factory. IIRC, the bolt pattern is just slightly off, i.e., not perfectly identical, so there are really only 2 ways to get it on there. This will work to your advantage.

In your case, since the Auto/Stick conversion means that your car was not balanced, and thus, was not marked in any way, I have the following suggestions:

1. Install the driveshaft and then drive the car. If you notice a lot of vehicle speed dependent noise coming from the rear end - remove the driveshaft and turn it 180 degrees (since you can't turn it only 90 degrees due to the bolt pattern).

2. Drive the car again and see if it's better or worse. If better, get under there with a file and mark the driveshaft and yoke. If it's worse, see #1...

A tip would be to make sure that you do your 'test-drive' over the same roads at the same speeds, otherwise, you'll have a hard time figuring out which is better or worse.

This at least gives you a baseline to start from. I wouldn't be too concerned about damaging the driveline with an out-of-balance driveshaft. If either of the 2 positions of the shaft are too poor to your liking, you can take it to a driveline shop and have them balance the shaft for you at minimal cost. The steel weights that you see on the shaft are harmonic balancers which must be there for quietest operation. HTH,
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Old 01-17-05, 04:42 PM
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Yeah, you're supposed to mark it and put it on the same way it came off. I wouldn't worry about it, I've always just put it back on there, never marked it. And I've never had any vibration at all.
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Old 01-17-05, 04:52 PM
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yea just put it on, I never mark it.
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Old 01-17-05, 05:21 PM
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In my 81 GSL I had the U joints replaced once w/ no problem. 2nd time I got vibration - had the shaft balanced- still vibration- trashed it. Stuck on a used one in my driveway that still runs smooth. With the white 81 7, I had the work done at the dealership. W/ replaced U joints got mega vibration so they replaced the whole thing. I think replacing the drive shaft & joints by a new combo is what MAZDA says to do. All you can do is try & see if replacing just the U joints works.
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