Classic Canyon Cruisers

Opening a Quadratrac
with MileMarker kit inside

February 24, 2007

In our efforts to better understand the Quadratrac, we got a chance to open one up that has a MileMarker part time conversion kit inside. You can't tell the type, 1:1 or 16% Overdrive, until you open it up. Before the QT was placed on the bench, we set it between a block of wood and a jack stand to check the chain tension. A little over an inch of slack. So the chain is worn out and needs replaced. Inspection under the Edrive shift plate finds a MileMarker shift collar inside. Once it is on the bench, we want to inspect the shifter. There is usually wear in the shifter component. Upon inspection, the shift collar retainer spring was broken in two pieces. The small piece buried in the hole was jammed kind of sideways at first. I dug it out with a chain saw file handle. Once the vacuum shifter was removed, I was careful not to let the retainer ball on the shift rod fly away. We discovered it was missing and longer spring had been installed to compensate. Since the rear output shaft bolt was already loose, we removed the yoke to peek at the seal. Looked clean. Once the low range unit was pulled, we saw that it had been lubed with Dexron. This is proper fluid for a part time conversion. The next thing that appeared out of the ordinary was some aluminum slag from a rapair weld on the very bottom end of the case. The chain could have broken the case at some point or maybe it had been set down hard a rock. When splitting the case, it is better to use a blunt brass drift to tap the seam apart. I don't have one and used a small flat end punch and a very light hammer tap to seperate the case at each of the two dowel pins. Once the case was opened, we disovered the sprocket assemblies and shifting mechanism for 2wd/4wd inside the sprocket appeared to be in very good condition. The plastic bushing for the MileMarker sprocket was in supurb condition as well.

At this point I put it back together for a future project. This MileMarker conversion kit will go into another case that has not been welded on or has stripped bolt holes. Then it will be installed in Ryan's (Gambler68) 78 401 J10 project. =8-)

November 2008 Update - Ryan needs this QT for his blue Cherokee.

Rebuilding the QT



What's the shifter look like?


Retainer spring for vacuum
collar broken

small peice buried in
collar groove

dug out with small file

remove E-clips

remove shaft while holding
thumb over retainer ball hole

shift fork w/nylon pads

retainer ball missing & longer
spring installed at some point

remove rear yoke

remove Edrive light switch

remove low range bolts

the 2 smaller ones stripped out


low range removal


planetary gear set

removing C-clip from planetary

lift planetary straight up

OMG! Dexron!

OMG! Old wound welded!

split the case - tap EASY!

small lip here to tap against

this end loose

this end a little tighter
! light tap !

this end loose

spread case gently at the
two dowel pin points

lifting back half of case

MM sprocket and shaft

MM bushing on the shaft