Driveline question

Post by **Legacy777** » Thu Oct 28, 2004 2:53 pm

Just a random question here. I was looking through the POS hayne's manual for my mom's yota truck, and mentions that if you remove the driveline to make a mark on it and the diff so that you align/mount it the same way.

I checked the haynes manual for the legacies it says the same thing. I don't recall if I looked in the FSM however.

Any particular reason for this? I didn't see how you could screw up putting the driveline on, and there wasn't any slop to have gotten it mis-aligned. Am I missing something?

vrg3 · Post by **vrg3** » Thu Oct 28, 2004 3:34 pm

I think it's just to minimize the small imbalances that arise from manufacturing tolerances.

The joints bolt together in more than one possible orientation, right? Like on the cars I've dealt with there were 4-bolt flanges that could be attached in any one of four ways (90 degrees apart)

So, presumably, at the factory they try each of the possible orientations and choose the one that minimizes overall imbalance. And the Haynes manual is advising you to try to keep it that way.

It's kind of like when you put brake rotors on... some people try each of the 5 possible orientations, measuring runout each time, and select the one with the lowest. They say they can actually feel an improved smoothness in the brakes because they've minimized the imbalance between the hub and the rotor.

'Course... what are you supposed to do when you put on a driveshaft from another car? My brother and I just bolted 'em on and forgot about it. I don't think it's that big an issue when you take into account the imbalance in the u-joints and all that anyway.

professor · Post by **professor** » Thu Oct 28, 2004 3:43 pm

supposedly some manuf. put the balance weights on the driveshafts in situ. You can usually see a flat weight pasted onto the shaft somewhere for balance.

In the case of a two-piece driveshaft I can see where it would really matter, if they were balanced as a unit.

I would think if the driveshaft was dynamically balanced after manufacture but before installation at the factory, it really wouldn't matter. I can't really imagine that the factory screws around with it at all.

I think to some extent that is one of those "stock" lines that appear in all Haynes manuals, a practice that leads to a bunch of errors making it through. I gave up on Haynes for the BMW, the Bentley manual is so far superior that its not even funny.

Post by **Legacy777** » Thu Oct 28, 2004 3:46 pm

I'll have to check the fsm to see if they mention it.

Post by **Legacy777** » Fri Oct 29, 2004 3:31 am

I checked the fsm, and there isn't shit in there about marking the driveline and diff......damn haynes.

evolutionmovement · Post by **evolutionmovement** » Fri Oct 29, 2004 5:15 am

Yeah, I think Haynes copies general advice to all marques. Like that BS about #1 TC during a belt change.

Steve

THAWA · Post by **THAWA** » Fri Oct 29, 2004 6:25 am

Or are you sure they meant between the shaft and the diff, and not between the u-joints on the shaft? I know the shaft is balanced from the factory, but I didnt' know the shaft and diff were balanced together.

Post by **Legacy777** » Fri Oct 29, 2004 2:43 pm

Basically they say to draw a line on the plate on the driveline that bolts to the diff. I don't see how you can get that alignment messed up to tell you the truth.....

THAWA · Post by **THAWA** » Sat Oct 30, 2004 3:23 am

Well it only mounts two ways right (because of how the bolt pattern is), the way it came from the factory and 180 degrees from the way it came from the factory. If the shaft and the diff are balanced from the factory then yeah I can see getting the alignment messed up, but then it'd so simple to just unbolt the shaft and turn it another 180 when you feel the vibration or whatever.

So that's how you could get the alignment messed up, but it's not like it's hard to just flip it if its out of alignment.

In otherwords, yet another reason to not listen to haynes

Post by **Legacy777** » Sat Oct 30, 2004 5:28 pm

These four bolts are evenly spaced out. So there are four possibilities to how you could bolt up the driveline to the rear diff. However there is a lip on the center portion of the diff that aligns everything up, so I still don't see how you can mis-align anything.

http://www.surrealmirage.com/subaru/ima ... P_3355.JPG

Unless hardy, you and I are talking about different things?

THAWA · Post by **THAWA** » Sat Oct 30, 2004 6:26 pm

we're talking about the same thing but I could've sworn the bolt pattern was rectangular instead of square. I'm probably wrong though.

I think the meaning about getting the alignment wrong would go back to the idea of the diff and shaft being balanced together, not the actual shaft mounting to the diff.

Post by **Legacy777** » Sun Oct 31, 2004 3:15 am

It may be rectangular.....that pic isn't close enough to tell. I'll have to see if I have any with a closer view.

fishbone79 · Post by **fishbone79** » Sun Oct 31, 2004 6:34 am

I just finished installing my newly rebuilt tranny, and only removed the diff from the carrier bearing forward... In actuallity, if you look at the flange, there is only one way it fits perfectly... It will fit 180 off, but the holes dont line up perfectly. I thought it was a fluke until i looked at the other two i had in the garage and it's true. The bolts will fit in the middle flange 180 off, but you will find it doesnt line up quite as exactly as the other way.

entirelyturbo · Post by **entirelyturbo** » Sun Oct 31, 2004 11:19 pm

The bolt pattern on the U-joint is not only rectangular, in fact, I think it bolts up one way and one way only.

After putting my tranny back in, I put the U-joint back together, and put two bolts in. I turned the driveshaft 180 and the other holes were in no way lined up. Now, logically, if I had it 180 off, it should still fit, and if I had it any other way, nothing should have lined up at all. Did that make sense to everybody?

I have absolutely no vibrations in my drivetrain, car drives smooth as hell. So I must have done it right.

THAWA · Post by **THAWA** » Mon Nov 01, 2004 2:22 am

so does that make it trapezodial?

entirelyturbo · Post by **entirelyturbo** » Mon Nov 01, 2004 4:55 pm

I'm not sure, although trapezoidal technically shouldn't work, because then nothing would line up unless it was perfect...

THAWA · Post by **THAWA** » Tue Nov 02, 2004 3:50 am

depending on how the trapezoid is shaped it can work fine like you stated. If two of the sides are perpendicular to each other and the same length, you could have two of the bolts go in fine, and then turn it and it be either too long or too short for the other two bolts.

legacycentral bbs

A forum for 89-94 BC-BF(BJ) Legacy Owners and Fans

Driveline question

Driveline question