Transmission Compatibility (for C-121)

[Vurge 157]

Last year I picked up a C-121 that seems entirely functional except for it is stuck in the high gears.  I've gotten some great advice as to how to go about with a repair, but I am thinking of purchasing an entire transmission so the machine won't be out of service for as long.  Does anyone know what machines have compatible manual transmissions?  

[8ntruck 6,358]

I am assuming that it is an 8 speed. I think any C series 8 speed will be a direct replacement.

 

If I am wrong here, somebody will be along to correct me.

[stevasaurus 22,229]

8ntruck is correct, but you may want to be aware of a couple issues.   Use this chart for model #'s and transmission #'s.  These will all bolt right in...#5091, #103907, #103916, #103918 these are all 8 pinion with 1 1/8" axels.  You may want to stay away from the #103916.  This transmission uses the #111199 needle bearing in place of the #1533 ball bearing for holding the differential carriage.  The 2nd thing to be aware of is the length of axle.  In all 4 of these transmissions, both left and right axles are the same length, so you can measure from the end of one axle to the end of the other and divide by 2 to get the length of axle.  You could also measure how much axle is sticking out of the trans case and compare to yours.    

 

 

[Ed Kennell 35,576]

I have had a couple 8 speeds that woud not shift the hi/low unless I pulled up on the shifter.

[stevasaurus 22,229]

Hey @Ed Kennell  do you know which ones you had to do that with ??  I have not heard of that before, and I wonder if it just was not an issue inside the transmission. 

[Ed Kennell 35,576]

38 minutes ago, stevasaurus said:

Hey @Ed Kennell  do you know which ones you had to do that with ??  I have not heard of that before, and I wonder if it just was not an issue inside the transmission. 

The one was the  312-8 that I recently  rigged for a snow plow and gave to my son.   The tranny seemed to function fine, but there was about a 1/8" vertical play in the hi/lo shifter shaft and you had to lift it to be able to shift.  I actually remover the shift lever and installed a spacer under the lever to keep the shaft in the up position.  Now it shifts easily.

The other 8 speed that did this same thing was too many moons ago and has long since been deleted from my memory data bank.   

I am not familiar with the innards of these trannys like you so I don't have a clue why or how this can happen.   Does it make cents to you? or scents or sense?     

 

You can see the spacer under the hi/lo shifter.

 

And that boot repair was by the PO ...not me.

 

 

 

 

Edited August 27, 2021 by Ed Kennell

[stevasaurus 22,229]

Yes, it makes since to me.  You just took the slack out of that shifter for up and down.  Not a bad idea if that is what is happening, but by lifting the shifter a little, you made the shifter work easier because it was more in line with what that shifter does.  Watch this and see if seeing how that shifter works doesn't explain what adding that washer did.  The thing to see, is that the shift lever moves that fork up and down by turning it from one side to the other. your washer took out the slack.  @Racinbob did the same thing with the input shaft on 3 speed transmissions to try to take the slop out of 3rd gear popping out of gear.

 

 

[Vurge 157]

My high/low shifter slips up and down very easily.  If it weren't for a horizontal bar across the frame blocking it, I'm sure it would just pop out completely.  I did try shifting it in the up position but no luck. 

 

@stevasaurus - thanks for transmission information.  Now I know what to look for.