Monday, February 18, 2019

Replacing the Input Shaft in Scarlett's Gearbox

Scarlett's gearbox's input shaft's splines were damaged when the clutch disk splines failed over time.  As the splines on the clutch driven plates wore, they damaged the splines on the input shaft.

Note the gouges on the splines.

Today, I got the part from Holopaw Ural in Florida, the only dealer who had it in stock.  IMWA (aka the mother ship) in Redmond, WA had said they wouldn't have more in stock till sometime in March; so I was fortunate to have Terry Crawford offer to call Gene at Holopaw to query him.  Thanks gents!

Here's the new input shaft, pricey but shiny.


While waiting for the part, I'd cleaned up the gearbox but hadn't cracked it open yet.  You see it below, the view from the rear.  I thought at this point I didn't have to remove the kick starter lever.  I would be proven wrong later.  On the plus side, I didn't have to remove any other levers or the output shaft's flexible coupling plate.


After removing the Allen head bolts securing the two gearbox halves together, a little bit of light tapping with a soft hammer separated the halves and I could see the gearbox's innards.

 The input shaft is the one with the chewed up splines.
It popped right out with no fuss.

It was then I realized, after a call to RichardM, that a hydraulic press was required to separate the bearing and collar right below the splines on the old input shaft!  

I did first try a bearing puller, but no joy, the collar was holding the bearing very tightly.


RichardM suggested simply driving to a machine shop and have them press it out and press the bearing and collar onto the new input shaft.

I called around, found a machine shop less than 5 miles away and they took me right in!

 Old input shaft secured below the metal plates,
pressure from above pushing the shaft down while 
the plates held the gear, bearing and collar in place.

Maverick Machine Shop's tech then used an Arbor Press and a socket to press the bearing and collar onto the new input shaft.  $45 later (minimum shop charge)
the shaft was ready:


Back in the garage, I popped the new input shaft into place with no issues.


The next 1-2 hours were then spent re-learning how to fit the two halves back together, making sure that the shift lever mechanism meshed on shifting mechanism crank on the side of the case.  I would end up doing this about 4 times, each time being a little bit easier.

Took me four times because I kept taking it apart trying to figure out the spring reset procedure in the Turtal Video that I'd been using as a guide.  A few more calls to RichardM and I was clued into the fact that:

The kick start lever had to come off so I could depress it's mount as part of the kick start spring reset procedure.  This took a bit of effort, some hammering and some light cursing to get the pin that holds the lever onto the mount out.  Note: next time I'll order a new pin from the dealer, too easy to bugger up this pin while getting it out.

Then, I was having trouble, after the pin was out, removing the actual lever!  RichardM clued me in again, use the gear puller I had tried on the input shaft bearing with no success.  Duh.

 The bearing puller make short work of removing
the lever.

Once the lever was off, and using a 16 mm open end wrench to turn the mount counter-clockwise while pressing down on the mount, I finally got the spring to "reset".  The kick start lever was installed with minimal fuss.

Since I had only used two bolts so far to secure the halves together, I then separated the halves by perhaps 1/4" (the amount I loosened the two bolts out from their mounts) and applied RTV sealant to the two mating edges.  Once done, the halves were bolted back together with all the bolts and the RTV sealant will "cure" overnight.

The splines look "mo better" eh.
I sure hope this is the last time I have to do this
particular repair.  It was a bit of a PITA.

I'll be assembling the gearbox onto the engine tomorrow, and putting Scarlett back together as well.

RichardM, my Guru for today's work:


Here's the Turtal video on the Ural gearbox's disassembly/assembly:  LINK

I think I'm one step closer to having a hydraulic press in my garage....

8 comments:

RichardM said...

You call tech support these days and you never know who you’re going to get...

dom chang said...

In my case I got great support! And, you looked quite comfortable providing it!

Jan Daub said...

Richard worked up a sweat on this one, had to take a break and cool off...

Great job guys. Glad it's back together.

dom chang said...

Won’t know for sure till the test drive but the gearbox acts as expected....can shift through the gears, the kickstart lever moves the shaft and feels under pressure.

Kofla Olivieri said...

Wow, looks like a lot of work.

dom chang said...

Swapping the input shaft itself is easy, it’s the dismantling and assembly that takes time and effort.

Brook Reams said...

If you have need again for a press, I have a 20 ton press in the garage.

dom chang said...

Thanks Brook, will keep that in mind. I do think there's a hydraulic press in my future though....