Transmission Poppet Ball Modification

M274 Mechanical Mule Knowledge Base
Post Reply
muleman7
Sergeant Major of the Gee
Sergeant Major of the Gee
Posts: 483
Joined: Mon May 14, 2007 6:36 pm
Location: Georgia
Contact:

Transmission Poppet Ball Modification

Post by muleman7 » Sat Oct 24, 2015 7:58 pm

I have come across Mules that shift hard between 2nd and 3rd. When I evaluate a mule I check the shifting between 2nd and 3rd with the engine off. I will shift into 2nd and with steady pressure try to push the gearshift into 3rd. Then when it's in 3rd with steady pressure I will try to pull the gearshift into 2nd. I find some transmissions will not shift even if you steadily increase the force. They will only shift if you bump or jog the gearshift.

I have concluded that as the 1/4 inch poppet ball tries to move up the tube away from the shift shaft it gets wedged and the gearshift must be bumped to allow shifting. This is caused by the ball creating a ramp at the edge of the tube where it meets the shift shaft after years of shifting.

My remedy was to make a plug that would already be in the tube allowing it to move up without wedging. I started with a 3/8 inch long plug but now make it 1/2 inch long. Because one of the mules I modified using the 3/8 plug would not shift with out a heavy bump. The 1/2 inch plug corrected the hard shifting.

I use a 1/4 inch O-1 Keystone Ground and Polished Drill Rod. I cut a length and chuck it in my drill press [poor mans lathe] and round it using a file. then polish it with 400 grit. I cut and grind it to 0.500 inch. I then heat it with a torch to about 1450-1500 degrees and quench it in oil that was heated to about 125-150 degrees. I do not Temper the plug. I clean it using a wire wheel.

I then Mic the spring and grind it to the correct length.

I grease the shift tube and poppet plug insert the plug, spring and threaded plug.

I now have a transmission that shifts smoothly without jogging or bumping the gear shift lever. This could be done for 1st-Rev and Low-High.

The pic of the Poppet Plugs came from mule transmissions. One is 1/8 inch thick and the other is 5/16 inch thick. That is why I ground a socket to remove the thin headed plug.

The thing that I would like to know is how does shorting the spring affect the load it puts on the plug during shifting?

My last pic is of tools I developed to assist in working on the M274 and A3 transmission. I can install a new synchronizer without pulling the engine. I install the 2nd-3rd spring and ball then push them into the tube using a length of the 1/4 inch drill rod ground on the end to allow the plug to hold the ball in place when the rod is removed. I insert the plug so the notch faces to the 1st-rev shift shaft. I then install the lock out plug and the 1st-rev shift shaft then safety wire the fork. I then finesse the mainshaft into position with the fork on the synchro hub. I install the 1st-rev spring, ball and plug then set 1st-rev to neutral and install the 2nd-3rd shaft through the fork and against the temporary plug. I CAREFULLY push / tap using constant pressure to drive out the temporary plug. If all goes well your home free. BUT if there is any gap between the temporary plug and the shaft the ball can pop out and you have to start ALL OVER. I then set and safety wire 2nd-3rd fork. Yes I have to retrieve the temporary plug.

Remove the Spring

Image

Remove the Ball

Image

Measure the Ball 0.250 inch

Image

Measure the Spring 0.905 inch

Image

Filing the Poppet Plug to round the end

Image

Marking the Poppet Plug length

Image

Cutting the Poppet Plug

Image

Measuring the Poppet Plug

Image

Heating Poppet Plug to 1450-1500 degrees

Image

Quenching Poppet Plug in Oil heated to 125-150 degrees

Image

Checking ground Spring length it should be 0.655 inch actual 0.658 inch

Image

Comparison of Original and Modified Springs and Ball / Plug

Image

Dimensions of Poppet Plug Heads [securing bolt] one is 1/8 inch tall and the other is 5/16 inch tall

Image

Modified 9/16 socket giving full contact to remove the 1/8 inch headed Poppet Plug

Image

Shifting parts collected over the years most from cannibalizing the M274 transmissions when I could

Image

Parts used to install the 2nd-3rd Shift Shaft Spring and Ball into the M274 transmission that has no separate external access
The 1/4 inch rod is ground to allow the temporary 2nd-3rd shift shaft plug to hold the spring and ball
The temporary plug is ground to accommodate the shift lock out plug [Pin, Straight, Headless] when the 1st-rev shaft is moved to neutral this allows the installation of the 2nd-3rd Shift Shaft. the pics below are how the tools are used.

Installing the 2nd-3rd Spring / Ball and the Temporary Plug

Image

Set to install the 2nd-3rd Shift Shaft and drive out the Temporary Plug. The 1st-Rev shaft must be in neurtal.

Image
Last edited by muleman7 on Mon Oct 26, 2015 4:26 pm, edited 1 time in total.
Mules are my passion
www.m274armymules.com

Auto Shop teacher
G-Lieutenant Colonel
G-Lieutenant Colonel
Posts: 1033
Joined: Mon Feb 03, 2014 12:46 am

Re: Transmission Poppet Ball Modification

Post by Auto Shop teacher » Sun Oct 25, 2015 2:38 am

Great information Charles, thanks for sharing. The transmission is probably the most complex part of the mule, and with all of your great photographs, it removes some of the mystery of what causes some of the problems of what we may run across, and MOST IMPORTANT is the help coming up with a permanent fix for our half century + old vehicles. Thanks!

nw5s
G-Master Sergeant
G-Master Sergeant
Posts: 107
Joined: Tue Jan 24, 2012 10:07 am
Location: Shallowater, TX

Re: Transmission Poppet Ball Modification

Post by nw5s » Mon Oct 26, 2015 8:56 am

Great post, muleman7! I believe John Emery of Emery Mule Supply is also doing something similar. chuckw will be installing new springs, "slugs," and caps in my A5 transmission. EDIT: Thanks to Chuck for giving credit where credit is due... and setting me straight!! :D

Bruce
Last edited by nw5s on Mon Oct 26, 2015 10:10 am, edited 1 time in total.
------------
Bruce/nw5s
1968 M274A5 Automatic Sprinkler Corp

Chuck W.
G-Lieutenant General
G-Lieutenant General
Posts: 5094
Joined: Wed Dec 18, 2002 1:00 pm

Re: Transmission Poppet Ball Modification

Post by Chuck W. » Mon Oct 26, 2015 9:10 am

Charles actually developed this "fix". John is using his information to mass-produce parts for the repair.

Charles Witt has been working on mules since the early 70's and is willing to share and post many of the "fixes" that he has developed over the years. I am very thankful for his involvement and willingness to share with us. This is the kind of thing that will help new mule owners understand what they are getting into, and will help old mule owners keep their mules in service. We are all in this together! Thank You!.

Chuck W.
G-Lieutenant General
G-Lieutenant General
Posts: 5094
Joined: Wed Dec 18, 2002 1:00 pm

Re: Transmission Poppet Ball Modification

Post by Chuck W. » Wed Dec 16, 2015 4:10 pm

Just received a set of John Emery's new transmission shift rail poppets, springs and plugs, and they look great! While my personal mule is shifting fine, I plan to replace the balls, springs and plugs with these new pieces to head off any future shifting problems. Great job, John! Thanks!

Image


muleman7
Sergeant Major of the Gee
Sergeant Major of the Gee
Posts: 483
Joined: Mon May 14, 2007 6:36 pm
Location: Georgia
Contact:

Re: Transmission Poppet Ball Modification

Post by muleman7 » Wed Dec 30, 2015 5:34 pm

Thanks Chuck for posting John's Production of the Poppet Ball replacement for the hard to shift mule transmissions.
I will post 3 pictures that show the complete assembly in comparison to the original. The actual Plug that John developed is 0.550 inches long and identical in length to the Lock Out Plug between the Shift Shafts. John's Plug is rounded on both ends and will move up the tube without binding. This Modification can be used for 1st-Rev, 2nd-3rd and Low-High. This will restore shifting back to new condition and should give new life to the transmission without future modifications.

John's Assy. I rotated one of the Caps to show the cavity that allows the full length spring to be installed.

Image

John's Assy. ready to install

Image

A comparison between John's Assy. and an Original Assy.

Image
Mules are my passion
www.m274armymules.com

Post Reply

Return to “MULE M274 Technical”

Who is online

Users browsing this forum: No registered users and 1 guest