Going through rebuilding my 1951 8N. I have replaced the main input shaft due to the fact that the pilot had worn caused by a frozen pilot bearing. Rebuilding hydraulics also, so I have the pump cover/cylinder off. If I grab the pinion coupling shaft at the trans end I can "rattle" it up and down a small amount. Is it normal for there to be that much clearance to the splines (don't think it is the bearing). Or should there be no detectible free play there ?
- Thread starter S10Vette
- Start date
TheOldHokie
Well-known Member
- Location
- Myersville, MD
Hard to evaluate that "rattle" metric. It's a standard SAE 1-1/2 x 10 spline Class B sliding fit and there should be a couple thousandths of clearance in order to facilitate assembly plus/minus any manufacturing tolerances. That could easily be enough you would be able to feel it. It isn't critical and the parts don't slide under load so it would be extremely unusual for there to be any wear on the splines.
What you are seeing is likely stackup of the normal manufacturing tolerances. For example I had a half dozen shafts made for that very application and I didn't specify an undersize tolerance on the drawings so the shop made them on the upper end. I purchased a batch of "standard" splined sleeves from a second manufacturer. Both were specified as Class B sliding fits but they wouldn't mate because of the lack of proper manufacturing tolerance on the shafts. I had to put the shafts on the grinder and take .001/.002 off the major OD of the male splines to get them to assemble. I can feel the clearance but it isn't much.....
TOH
I put a dial indicator on it, and it moves up and down a total of .016". It does not appear to have any noticeable rotational freeplay though. Does the front mainshaft bearing affect preload on the rear countershaft bearing in any way ? Not that I really think it is the bearing.
TheOldHokie
Well-known Member
- Location
- Myersville, MD
That would be a large deflection for the slip fit. But you would need to measure the deflection in the joint not the supported assembly for it to be a meaningful metric.
TOH
Well, now I am feeling a bit foolish. I had not snugged the input main shaft bearing housing/throwout bearing assembly up yet and that left no preload on the countershaft bearing, so that is the freeplay (in the bearing) that I was feeling. Once I torqued the 4 bolts up, there was no detectable freeplay in the Coupling Shaft other than of course it slides back and forth on the splines. Doh !
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