Why mark driveshafts and yokes? (1 Viewer)

Joined
May 27, 2012
Messages
120
Location
Temecula, California
I am replacing the u-joints in my '72 FJ40 and have read that it is important to mark the yokes and driveshafts before dismantling. So I did.

However, now that I have everything dismantled and I'm looking at the yokes/shafts/etc, I don't see why marking up the parts is important. All the parts look symmetrical - i.e. it doesn't appear like it matters how the yokes are reinstalled.

Can someone explain what would happen if I don't reinstall the parts exactly as they were before I removed them from the shaft?
 

Toyoland66

SILVER Star
Joined
Feb 3, 2004
Messages
556
Location
Colorado
The shaft is balanced as an assembly from flange to flange, even though it appears symetrical there could be some variance in each yoke which would throw off the balance of the shaft if assembled 180^ from where it was balanced.
 
Joined
Feb 6, 2002
Messages
15,222
Location
OC, CA
It is not just balance; the shaft needs to be in the proper "phase". When U joints operate at an angle, the rotation of the shaft speeds up and slows down twice for each revolution. You want the two ends of the shaft to match in rotational speed, so it doesn't vibrate.

There is a Wikipedia entry for universal joints if you want to know more detail.
 
Joined
Sep 3, 2007
Messages
8,871
Location
New Zealand
The yokes must end up in line like this:

DriveshaftYokes.jpg

:cheers:
DriveshaftYokes.jpg
 
Joined
Dec 5, 2009
Messages
151
Location
New Zealand
If hypothetically speaking you took a cruiser in to a dealership and after coming back there seems way more drivetrain noise is it possible they got this wrong and now my propshaft has a bit of resonance going on?

They "did work on the driveshaft"
 
Joined
Sep 3, 2007
Messages
8,871
Location
New Zealand
If hypothetically speaking you took a cruiser in to a dealership and after coming back there seems way more drivetrain noise is it possible they got this wrong and now my propshaft has a bit of resonance going on?

They "did work on the driveshaft"

It only takes a minute to look underneath and check.

:beer:
 

Toyoland66

SILVER Star
Joined
Feb 3, 2004
Messages
556
Location
Colorado
If you pull the caps off of the u-joint and rotate the flange 180* and put it back together the driveshaft is still in phase. The only way for the shaft to come out of phase is to take it apart at the splines.
 

78fj40mg

TLCA #23510
Joined
Sep 13, 2008
Messages
4,072
Location
PNW, WA.
If you check the drive shaft you'll see balancing weights welded on the shaft, if the weights are reversed the shaft will be off balance and vibrate. Vibration is not a good thing for these rigs. Mark U joints and yokes and you'll be happy with the results.
 

Users who are viewing this thread

Top Bottom