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Model 20 propshaft binding


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Greetings everyone.

I have recently replaced the long propshaft with the bevel gear on the end, as well as some work done on the universal joint and removed lots of play.  I've managed 20 miles or so and all seemed fine, however the propshaft seems to be jamming up and leaving the car unable to move.  The rear axle and differential appear to spin freely, as does the gearbox and propshaft when seperate.

Maybe I have tightened the propshaft too much and I need more play - does anyone have a figure for the play or backlash on the propshaft?

Maybe I have fitted the radius or suspension arms too tight? Is there a procedure for this?

Any other ideas as to what could cause this binding between the rear axle and gearbox?

 

Thanks in advance

 

 

hup3.jpg

hup2.jpg

hup.jpg

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Well, first, it sure looks like your pinion gear is worn to beat hell.  Yet, you say you replaced it?  From that camera angle and that last picture, it appears the gear teeth are half worn off.

 

My second thought is that that same gear, last picture, is protruding too far from the mounting face.  I wouldn't expect to see the roller bearings that close to, or even edges outside, of the race.

 

If, as you say, all is free apart, but binding together, then the only logical explanation is the gears are being jammed together when you tighten the assembly.  I don't think you have enough lip there to put in a spacer, so the location of the pinion will need to be addressed....

 

My two cents, from fooling with a Model 20 since 1976.....

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Thanks trimacar

 

The photo was a little poor but the gear is certainly brand new - this was built from a single piece by a very experienced gear cutter - Brentwin Gears in the UK.  It may have taken him 15 months to manufacture, a little longer than the 1 month he originally suggested, but it looked like a good job and was priced only 20% higher than quoted - a fine deal in this industry!

 

He also broke the original bearing on the shaft which was unobtainable so I had to find and get a different bearing machined, hence the newer bearing sticking out a bit.

 

Unfortunately none of the veteran car or gear specialists I spoke to were willing to take in the axle/propshaft to repair it, so I've had to strip it a piece at a time, try and work out clearances and refit with the various contradicting pieces of advice from each of the aforementioned specialists!

 

I think I might try adjusting the play in the propshaft by adjusting the outer tube and give it a go.  Strangely it managed 20 miles or so after the rebuild before binding.

Back to the drawing board!

 

Thanks again

 

 

 

 

 

 

 

 

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On 8/15/2020 at 5:31 AM, trimacar said:

If, as you say, all is free apart, but binding together, then the only logical explanation is the gears are being jammed together when you tighten the assembly.  I don't think you have enough lip there to put in a spacer, so the location of the pinion will need to be addressed....

 

My two cents, from fooling with a Model 20 since 1976.....

I agree^

 

When I rebuilt mine, I "set up" the ring and pinion with just the ring gear side of the rear axle housing, that side bearing and the tq tube w/the shaft/gear in place.  This allowed me to set the pinion depth easily and be able to see what was going on in the process. That may be something that could help -remove the driver's side axle housing, then install the tq tube and operate it.  You should be able to see what's causing any binding.

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OK on the new gear, I apologize, the shadows in the picture make it look like it has wear.

 

The Hupps were strange, in that the gear and the shaft are all one piece, the gear is not removable.

 

I'd think some depth measurements would help tell you how the pinion is fitting in the gear.  I also wonder if you're getting some slop in the ring gear that's making it move over toward the pinion, your comment that you drove it and THEN it started binding is unusual, but may be a clue for you.  I vaguely remember that there are some plates and roller bearings in the rear axle, maybe something has shifted...

 

Good luck dc

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Thanks Guys.  I've checked the pinion, and the gear seems to have lined up nicely with it.  However, I shall give it a good check again, plus check for excess slop in the ring gear.  Fingers crossed something obvious will pop up.

 

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