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I Guess My Driveshaft Wasn't Straight After All....


radio9phs
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Did my five speed swap.  Took care to try to align the drive shaft/center bearing.  Had issues with transmission popping out of first gear.  Moved transmission more to the right.  Driveshaft still lined up vertically but must have introduced some lateral bend.  Began to notice a 'clinking' noise from down below. 

This is what I discovered upon investigation.  I am assuming this was related to the noise.  By the way, are any washers to be used in securing the guibo?

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I've read, studied, and applied the drive line alignment method described here by the right honorable and eminently venerable Senator Bill Williams.  With all due respect and humble apologies to my highly esteemed mentor, I still ended up with vibrations and shortened guibo life, both on my car and on our Lemons car.  Perhaps my vision isn't good enough to properly determine whether the gap between the flanges and the guibo remain equal while I rotate the assembly.  Perhaps my general incompetence precludes me from successfully completing even the simplest of tasks.  In an effort to reduce the impact of my disabilities, we fabbed up a fancy drive shaft alignment tool as described here, but that only served to validate that our drive shaft wasn't perfectly flat from front to rear.  Note that the drive shaft alignment tool only serves to measure whether the drive shaft is in a horizontal plane from front to rear, and does not indicate whether the drive shaft is properly aligned with the transmission.  As we've inverted the rear subframe mounts on both my car and on the Lemons car, we expected that the trailing end of the drive shaft would have to rise to meet the differential, and in both cases it does.  So the drive shaft alignment tool above wasn't of much value to us.  As the trailing portion of the drive shaft contains two universal joints between the center bearing and the differential, the alignment of the leading and trailing portions of the drive shaft is of lesser importance than the alignment of the transmission with the center bearing.  So we focused our attention on coming up with ways to determine whether the transmission output flange is pointed directly at the center bearing.

 

Mark (who goes by various user names on this forum, including Orphix), suggested that by replacing the guibo with a solid disc the same thickness as a compressed guibo, we could steer the transmission and drive shaft as a single unit.  After identifying the correct positions of both the transmission and the center bearing, we could replace the solid guibo with an ordinary guibo.  Voila.  Eric (who goes by sl0ride on this forum) suggested that making 4 bolt sleeves as spacers would be far easier and would require less material than fabricating a solid guibo.  Mark agreed, and fabricated 4 spacers out of cylindrical aluminum stock.  He cut the stock to the same length as the thickness of an 8-hole guibo (NOTE: an 8-hole guibo is NOT the same thickness as a 6-hole guibo) that's been squeezed by proper guibo bolt torque , machined holes down their centers to allow the guibo bolts to pass through, then machined the ends of the spacers to slightly conical points to avoid interference with the raised portions of the transmission and drive shaft flanges.  Imagine thick aluminum bolt sleeves with tapered ends.

 

With our newly fabricated metal sleeves in hand, we simply held the drive shaft and center bearing up in the air behind the transmission, slid a set of 4 guibo bolts through the drive shaft flange, slid the sleeves over the bolts, fed the tips of the bolts into the transmission output flange, and tightly fastened nuts onto the bolts until the transmission and forward section of the drive shaft could be aimed as a single fixed unit.  We loosened the transmission mounting bolts, positioned the center bearing so that it would connect to the tunnel, and noted that we had to raise the rear of the transmission 1/4" and lower the center bearing about the same amount.  (Our Lemons car had no floors in it when we started, and the car was in a horrendous front end collision earlier in its life, so we weren't too dismayed to learn that the motor mounts, transmission mounts, and center bearing location were pretty far out of alignment.)  After bolting everything in place, we removed the fancy aluminum sleeves and installed the guibo.  Drive shaft vibration is gone, and the guibo has lasted several races with no indication of any problems.

 

One could probably make similar spacers out of metal tubing, or make a guibo out of some dense wood, and achieve the same results.  Our Lemons team has a tendency to do things in the most difficult, professional, and overly-engineered fashion possible because (a) we have a bunch of engineers and wannabe engineers on the team (me included); (B) Mark and Eric have access to lots of fancy machine tools at their places of employment, and; © it's the Lemony thing to do.

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One trick is to spin the driveshaft slowly while watching for flex in the guibo. Works great for me.

Sent from the BMW CCA Octoberfest in Monterey CA

i do the same thing except do it with the bolts slightly loose so you can see the gap when it is out of line.  this is a pretty simple process.

 

the only thing that matters it the alignment of the FRONT half of the driveshaft to the tranny.  back half is not relevent.  never understood the usefullness of those stick alignment tools that just measure the front and rear driveshaft pieces and ignore the tranny.

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 He cut the stock to the same length as the thickness of an 8-hole guibo (NOTE: an 8-hole guibo is NOT the same thickness as a 6-hole guibo) that's been squeezed by proper guibo bolt

William, very helpful post. So would the proper "thickness", or length, of the temporary adjustment spacers, be the same as that of the metal sleeves found on the guibo since I assume the bolts compress right down to the sleeves?

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If the alignment sleeves that you made are the same length as the metal sleeves in the proper (6 or 8 bolt) guibo, why not take an old broken up guibo, cut the rubber away and use the salvaged sleeves from the old guibo itself?  That would save a lot of machining, drilling and cutting...

 

mike (not an engineer but happily MacGuyvering things)

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@mike,

 

I think that approach would work, but it would depend on the condition of the sleeves in the guibo.  If the guibo has been mangled, I suspect the sleeves would also be beat up.  Mark machined our fancy guibo spacers so that they were all the same length within some ridiculous aerospace/milspec tolerance--like 0.0001".  I also used a hand file, Emery cloth and steel wool on our transmission output flange and drive shaft flange to remove any imperfections that might throw off the alignment.  The results were great, but the effort may have been excessive.

 

You could probably use the sleeves from a dead guibo, but I recommend measuring them closely, hand lapping them to equal lengths if necessary, and doing the same to the flanges if their mating surfaces have been damaged.

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Great thread, folks.

 

(Additional data point: I notice guibo stress after a race weekend or session where I've managed to pull off an accidental, overly-aggressive downshift (if the tires don't break loose, then some of that stress/energy is absorbed by the guibo) ... check 'em often). -KB

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Remember the discussions about compressing the guibo before install? That "clinking" sound may have been the guibo hitting the underside of the shifter rod housing area (from my experience). Even with proper installation (compress guibo until bolted properly) it is 2mm away from the housing. Scary. You'll see wear on the that area of the tranny. If it was hitting hard, it could tear your guibo as well.

The huge stainless hose clamp, available at your local hardware store is perfect for compressing a used guibo to install on tranny and dshaft.

As for seeing misalignment, it is very evident, as there is a ridge on the guibo that is straight, and as you turn the dshaft it will appear to deform if the alignment is not true.

I used a thin flat washer under the rear transmission mount to raise the tranny slightly. I got the alignment perfectly straight, vertically. I didn't have any issue horizontally, but isn't there adjustment in the rear tranny support bracket for horizontal movement? Be careful. Any SMALL amount of tranny adjustment is HUGE at the cooling fan. IT'S VERY CLOSE TO THE RADIATOR.

Hope some of this helps.

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