Idiot and drive shaft

[zachmac]

I'm the idiot. In my zeal to clean up and paint the driveshaft and refresh the u-joints, carrier, and guibo while at it, I neglected to mark the assembly before took I out the two u-joint. So now of course I don't know what the relationship between the front shaft weight and the two rear shaft weights previously was AND I don't even know which end of the rear shaft used to be the front. If I knew the second I'd at least have a 50/50/90 shot at correctly orienting the front to rear shafts BUT as I don't even know that I have four possible orientations. So, opinions on options (and no, me not being an idiot is not an option left):

Option 1: take the whole assembly to a shop (about an hour drive each way) that can balance the entire assembly put together

Option 2) Put it together and hope, but I could on theory have to remove it, press out the u-joint and try again up to three times while performing a dangerous up on stand running rear end test each time in between.

If I elect for option 2 it seems I would start by assuming I want the bigger of the weights on the rear shaft toward the differential as that is clearly the most out of round shaft location and that would put it nearest the strongest resistance to wobble.

Does anyone know if this is really even an issue? What I mean is was the assembly originally balanced together or was each shaft just balanced individually? If it is the latter then the orientation of the two shouldn't matter much as the u-joints are pretty much self centering given that they use the circ clips all around.

[azruss]

All my long driveshafts have the counterweight toward the front of the car. I have driven some spiders with a lot of driveline vibration and my conclusion was it was assembled 180 out. If it were me, i would take my best guess and test drive it. You've got a 50-50 chance of being right. You probably don't even have to test drive it but can run the car on stands.

[zachmac]

All my long driveshafts have the counterweight toward the front of the car. I have driven some spiders with a lot of driveline vibration and my conclusion was it was assembled 180 out. If it were me, i would take my best guess and test drive it. You've got a 50-50 chance of being right. You probably don't even have to test drive it but can run the car on stands.

But, my long shaft has a weight on each end. That means I don't know which is the front or back AND that means there are four possible orientations. 50/50/90 goes to 25/75/95.

[spidernut]

I did this once, but caught myself before cleaning up and repainting everything. I was able to match up the amount of the PVC undercoating to the drive shaft segments since the undercoating was sprayed after assembly of the cars.

You could take it to a shop and have it balanced to be safe. I'm personally not a fan of trial and error methods.

[azruss]

It seems to me, from a manufacturing perspective, that it would be far more cost effective to balance each shaft individually rather than the whole assembly. So this may not be as big a deal as you think.

[zachmac]

It seems to me, from a manufacturing perspective, that it would be far more cost effective to balance each shaft individually rather than the whole assembly. So this may not be as big a deal as you think.

I would THINK so as well, but does anyone KNOW? I guess I could just go have each shaft balanced / checked individually as that is doable much closer to home and cheaper.

[hayesbd]

The Fiat shop manual states that you should mark positions prior to disassembly to maintain the balance, so it looks like these were balanced as a complete assembly. It also states that there are assembly marks on the forward parts, so perhaps there are also some match marks on the rear segment as well? I'd look for some punched dots or something similar.

Good luck,
Brian

[chrisfiat]

assemble it and take it to the balance shop, this is the least stressful , and best option at this point, and you will have a known good driveshaft

[DieselSpider]

If you cant find any punch or scribe marks from a previous service on the shaft then I agree its time to take it to a drive shaft shop to have it assembled and balanced as an assembly. Its not worth the potential for damage to the transmission output bearing/seal, rear axle pinion bearing/seal or carrier bearing along with the potential for collateral damage to the bottom of the vehicle.

[zachmac]

assemble it and take it to the balance shop, this is the least stressful , and best option at this point, and you will have a known good driveshaft

Pretty much the conclusion I've come to as well.

[htchevyii]

I forgot to mark mine and it vibrated so bad that it was undrivable. Neither of the driveshaft shops in my area had the proper adapter to balance it. I bought a used one for $40 on a Ebay and started over.