The drivers side axle is bottoming out on the 3rd member pin. I have tried 4 axles out of 65-66 F100 axle assemblies with the same issue. The problem reared it's ugly head when the drivers side axle walked out on me while driving down the highway. I put a new bearing on a good axle the same length and the axle binds up when I tighten the axle retaining plate nuts. The same axle works fine in the right side of the truck. I replaced the 3rd member with a known good unit and the problem is still present. I believe this was the cause of the original axle walking out on me. The previous owner had the rear axle assy replaced for better highway gearing.
I inquired at "Strange" and the tech guy replied that I must have a bent tube. I do not understand the thought process there. 5th page, wow.
I had this happen.... Twice on my first Tudor, running an 8" ford. Had a bad vibration at 55 mph too. 1st time- beat the bearing and lock ring back in and welded the lock ring. This was drivers side, happened on the freeway with a trailer hooked up going to Billetproof. 2nd time- happened 3 days layer on return trip home. Towed it home. Got two used but good true axles. Installed 2 new bearings & locks and welded the locks. Bearings went out within a few hundred miles. Changed to a '57 Ford 9" rear and it was smooth as silk afterwards. I think your housing / tube is bent back as viewed from above.
One thing that I have discovered about a 9" Ford is that sometimes the axle is too long, I am sure that there is a reason for this. If you can slide the axle into the axle gear then you most likely don't have a bent axle tube. You are talking about the axle hitting the cross shaft for the spiders correct? Here is what I do when I am setting up any 9" rear. First I slide the axle in and see if it is going to hit the cross shaft. If it does then I slather the splines with marking compound, I am a machinist so I keep a tube of Prussian blue around but you can accomplish the same thing with grease. Now slide the axle in until it bottoms out on the shaft and pull it back out and see how much spline you have left. This is also a good time to check and see if one side of the axle is wiped off more then the other which is an alignment indication. You should have some spline left over in which case you can take an angle grinder to the end of the axle for clearance and slide it in again. keep taking a little bit off until you are no longer hitting on the cross shaft.
Yes, the axle is hitting the cross shaft, I am heading out now to do more figuring. I've been fighting this for longer than I care to admit.
I would pull the 3rd member, so you can get it on a table and see exactly what the problem is. It's not too difficult, especially in a pickup. BTW I have been driving a '65 F 100 for 43 years !
I say fighting, but I am calm and relaxed, just perplexed. I did some measuring, from the cross shaft to the outside edge of the tube is 28". From the outside of the bearing to the tip of the axle is 27.75". This 1/4" is where the problem lies. The bearing sticks past the tube about 1/8" or so, so that the bearing retainer sits against it. If I have 1/8" cut off of the axle will there be enough spline to allow the shaft to slide all of the way in? I am still trying to find the stock measurement of an F100 axle with a 57" axle tube. I put grease on the end of the shaft to see how far the axle splines went into the diff splines and the results were inconclusive, grease everywhere. I am told that both axles in an '65 F100 are the same length, but my axles only fit in the passenger side.
I just put in a good 3.73 trac loc unit, I pulled out a 2.75 open 3rd member thinking it was the problem.
Do not cut before you check just the way that I described. I have never had to shave more than an eighth off of one. You can even put some marking compound on the end of the axle and see if it is hitting the cross shaft at all, you may just be hitting a burr that does not let you bottom the axle out in the axle gear. Check first and cut last always.
Put the axle in till bottomed out..Put tape on the od of bearing at the flange...Pull axle out and compare the amount of bearing that went in the housing to the actual depth of the housing bore..Example: 1/8" diff and you take 3/16" off axle so you end up with 1/16" clearance at cross shaft..Spline engagement is about an inch..
Ok, I'll try less grease this time. The 2.75 3rd member I pulled out had obvious wear on the shaft where the axle had been rubbing it, and the bearing retainer corners were bent around to conform to the bearing also, indicating that the axles was not fully seated. Thank you for the advise.
The axle bearing when seating does stick outside of the tube aprox .100 or so, but thats the same thickness as your backing plate. Dont know why your bearing retainer ears are bent over from drawing the assembly in tight? Usually there is 1.375+ of spline, that if you needed to cut 1/8-3/16" off your axle, there will still be full spline/side gear contact on your 28 splines.
I'm going to cut one off tomorrow. Thank you for the info. I hope the axle has enough spline to go all of the way in once the extra length is cut off.
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