D18 Wear

I'm inspecting my D18 parts to see what I need to order beside the rebuild kit. As far as the splined shafts are concerned at what point (thousands of a inch) would they need to be replace because of spline fit looseness in a gear splined bore.
Which part usually wears to cause the looseness, the shaft or gear, or both.
Generally are there any specs on the D18 internal "fits". Thanks !!!!!!!!

 

the intermediate shaft is it's Achilles heel, especially on the earlier, smaller diameter sizes.

 

Except for the driveshaft yoke, I have never seen T/C splines that needed attention. The intermediate gear/bearings/shaft are the most wear-prone part of a D18. With shaft wear, the intermediate gear eats away at the thrust washers, contributing to more wear and noise.
I have rebuilt D18's in the past without even replacing the output bearings because they were in excellent condition. Just make sure you get clearances correct with the appropriate shims.
-Donny

 

Its a good question. I would think new ones dont have any noticeable play so use your best judgement. Iv seen the input bull gear so worn out half the splines were gone and peened over.

 

I had a chance to look at my parts and all splined fits look good. The only possible issue is the output shaft to output shaft gear bore seems a little loose. With my calipers the shaft measured 1.3125 and the bore in the gear measured 1.3150. Don't know if this is a issue or not?????

 

Does anyone have a new or nos d18 output shaft and output gear? I would like to know the bore dim in the gear and the shaft diameter where the gear rides. Want to compare to my dims above. THANKS, back to my eggnog!

 

The shaft diameter is a nominal standard size 1.250, 1.125 or 1.000 diameter. The gear bore should be similar as the needle bearings are a nominal size, if your hole measures an oddball size outside of a normal fractional size it is worn. A couple of thousands is ok, if more than about .004-.005 it is to much, the shaft usually always wears before the gear does. the gears are harder than crap.

 

Rather than trying to measure bores and diameters of splined shafts for comparison, the more important factor is the fit of the two parts together. Is there any slop or "play" when the two are assembled? With splines, there is more than just bores and diameters. The width of the splines often makes the fit reletive to each other.
-Donny