Jump to content

Model 20 Gearbox problem


Recommended Posts

Greetings again. 

Having double checked my propshaft and found nothing wrong, I've opened up my gearbox and found the cause of my jamming up problem.  On the lower gear (arrowed) there is a pin that appears to be damaged (arrowed in second photo).

 

When the pin slides in the gearbox is free to move, but when it slides out the gearbox jams up.  Can anyone advise what this pin does and how it should look?  I've had a good look on the search function here but couldn't find anything specific.  Does anyone have any diagrams or info?

 

Thanks again

 

hupg.jpg

hupg2.jpg

Link to post
Share on other sites

I'd say you're going to be taking that apart to fix.  Not that difficult, just make notes/pictures as the Model 20 gearbox comes apart, and goes back together, in a very specific sequence.

 

Is that top gear really worn, or is it just a camera angle trick?  Good luck with fix, while apart I'd check all the bushings, I had two in my gearbox that were slap worn out. 

  • Like 1
Link to post
Share on other sites

Gearbox is stripped and things are a little clearer now.....

I assume I just need to make up 8 new pins and clamp the parts together again with the bronze sleeve reattached to the hub.  Looks like the other 7 pins must have snapped off at various times.  I only found the remains of the one final pin in the housing and don't recall any bits falling out in previous oil changes so must have been like that for many years.

 

 

HUPg.jpg

HUPg2.jpg

Link to post
Share on other sites
3 hours ago, trimacar said:

I'd say you're going to be taking that apart to fix.  Not that difficult, just make notes/pictures as the Model 20 gearbox comes apart, and goes back together, in a very specific sequence.

 

Is that top gear really worn, or is it just a camera angle trick?  Good luck with fix, while apart I'd check all the bushings, I had two in my gearbox that were slap worn out. 

 

Thanks for that.  Wasn't too bad in the end.  Bit of a mind challenge to get the gears out though!

Think it was the camera as the top gear looks pretty good....

 

HUPg4.jpg

Link to post
Share on other sites

Yes the gear looks good!  I remember doing my gearbox, it wasn't that difficult to take apart or put together, I just remember that if you tried to do things out of order, the next piece wouldn't go in.  

 

 I think it was the bushing in your picture, plus the very rear bushing in the housing itself, that were bad on mine....so needed new bushings....I don't have machine tool capability, took it to a friend with a machine shop, we never discussed price.  When done, he told me it was a big job, and he couldn't charge me the amount the hours cost.  He was very fair with me, but it was still hundreds of dollars...

Hupp restoration 007 transmission primer.jpg

Link to post
Share on other sites

Look closely at the drawing of p/n 247.

I think you need to make a new bushing,I think it should be the total length of the gears.Yours looks sheared off.Looked at one again,there seems to be two pieces(?) to the bushing,or one piece with an oil groove.You will find out when you press it out.

Ken

Edited by KenHupp20
Add information (see edit history)
Link to post
Share on other sites

Yes, the bushing has snapped off at that point. I was thinking of getting the grooves lined up and brazed?  I know a very good welder, but if not I guess I'll need to get someone to machine a new bushing made up.  I'll check that it's all one piece all the way through as well.

 

The lower gear may be more problematic. What initially looked like a beautifully machined finish to the back of the gear for some reasons of clearance became suspicious when I realised that there was nothing to clear. There surely can't be a reason for this gear to be narrowed so I'm guessing it has been beautifully turned down by the reverse pinion.  There is no excess wear or damage on the other gears or the arm though.

 

So I'm looking at getting a new gear made up, new bushing for that gear, new bushings x 2 for shafts on the case, 8 x pins and then reassembly.

 

 

hupg5.jpg

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...