driveshaft for Overdrive on D18

M

maunster

New member
How do I figure out the length of driveshaft needed for an overdrive on a d18?I currently have a three speed installed.... But I have a shorter driveshaft for a four speed, will this work? Any experience or thoughts? Thanks!!
 
With all 4 wheels on the ground and everything is installed, measure from yoke of output from transfer case to yoke of differencials. Then do the samething for full droop of axles. Might be difficult if you don't have 4 jack stands supporting the frame while axles and tires are hanging in the air short of hitting the ground, then measure at the same points previousely mentioned. Having a vehicle lift would help, but I have used 4 jack stands.
 
scooter said:
with all 4 wheels on the ground and everything is installed, measure from yoke of output from transfer case to yoke of differencials. Then do the samething for full droop of axles. Might be difficult if you don't have 4 jack stands supporting the frame while axles and tires are hanging in the air short of hitting the ground, then measure at the same points previousely mentioned. Having a vehicle lift would help, but I have used 4 jack stands.
Click to expand...

You did not read his post correctly.
 
What I did for mine was measure from the approx center of where a u-joint cap fits in one yoke to the same position in the other yoke.

I took that measurement to a driveline shop and they did the rest, also accounting for the slip yoke travel.

Easy button for me.
 
Thanks for all the help guys!!! I have another question..will an overdrive thats currently on a d18 work on any other d18? Or is there differences between similar d18's? I've heard about there being gear teeth number differences......any idea?
 
Yes, the differences depend on the transmission the transfer case is mounted on, which determines the bull gear (some call input gear) used. In an overdrive, the bull gear is replaced with the od's output gear, some call the bowl gear.

For a Scout, look for a 29 tooth 6 spline. If it's a real early Scout 80 with a d18 that has the 1 1/8" intermediate shaft, you might need a 26 tooth 6 spline. It's best to take the pto cover off the transfer case in the receiving rig, and see what's there.
 
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