As many Comanche (MJ) (Manly Jeep) owners have now found out, there are very
few options when it comes to lifting the back end of Comanches! Pieces from
kits from XJ's will work on the front of the MJ, but not on the back end,
primarily because of two reasons:
- The stock rear leaf pack on an MJ has more arc that a stock rear leaf pack
on an XJ. This means that an add-a-leaf intended for an XJ will not give
the same lift on an MJ. (I found this out the expensive way, when I first
bought the Rugged Trail lift intended for an XJ, where Rugged Trail didn't
have a different add-a-leaf specific for the MJ. Total lift gained was
about 1 inch instead of the advertised 3.5 inches.)
- The stock rear leaf pack on an MJ is significantly longer than the leaf
pack on the MJ. In fact, the MJ leaf packs are some of the longest
available for any mini-truck! This is great news when it comes to
designing the suspension for maximum wheel travel, but it means that you
can't use complete replacement leaf packs from an XJ (or another source).
Over the years, I have come to the conclusion that there are about 3 ways to
best modify the rear suspension, depending on the amount of lift you want to
gain and the type of ride. I'm going to call these Stages 1 through 3.
Stage 1: Leaf
Pack Rebuild
Oddly, Stage 1 is
more expensive than Stage 2. But it still is affordable if you find the right
spring shop. It's ideal for people who want added payload and/or a lift of 1-3
inches. This section is short because it is relatively straight forward and
simple. As stated, it's hard to find add-a-leafs made specifically for the MJ. I
believe that Trailmaster provides one, but that is the only one I have ever
heard of, and I have no experience with it, nor have I heard how it works. The
answer is to visit the local spring shop and have some custom leafs made up.
Numbering from the top leaf down, I had #2 and #4 replaced with ones which were
slightly thicker and more static arc. Installed, it cost about $125US. The
spring shop should be able to answer your needs whether it be increased payload
(usually means a thicker spring) or same payload and good wheel travel (usually
means a spring of the same thickness, but more static arc to provide more loaded
arc). This, combined with longer shocks, will alone provide you with decent
wheel travel. No-where near what is possible because of the amount of static and
loaded arc in the leaf packs, but still very acceptable. The rear brake line may
be too short after this conversion. The frame mount of the brake hose can easily
be bent or even re-mounted to allow the brake hose to work with anywhere up to 4
inches lift.
Stage 2: Rear
Spring Over Conversion
I ran with regular
spring-under, 3.5 inch lift design for a couple years. When I decided it was
time for 33's, I looked at my options. Remaining with a spring under is not
really desireable because of the amount of arc required in the leaf packs. Ride
quality can be okay even with lots of arc (soft spring rate required), but wheel
droop is limited because the shackle will "bottom out". One choice was
to use a longer rear shackle. But the MJ rear shackle is already a decent length
(XJ owners regularly swap to MJ rear shackles), any longer may affect lateral
control. The other choice is a rear spring over. A spring over on a Comanche is:
- cheap (cost me under $100US, including the beer required during work), - quick
(took me and a welder friend a half-day), - immensely improves wheel travel -
retains good ride quality - provides between 4.5 and 6.5 inches lift, no lift
blocks Parts required: - 8 of 1/2" X 7 or 8" grade 8 bolts and lock
nuts - 2 XJ U-bolt plates - 2 new spring perches - a welder - new brake hose -
the original won't be long enough - longer vent hose for the axle - the original
also isn't long enough The grade 8 bolts replace the U-bolts. The XJ U-bolt
plates can be found at any wrecker. They sit on top of the spring pack, and are
what the XJ U-bolts tighten up against. The new spring perches should be able to
be purchased at any spring shop. You will need axle tube diameter and spring
pack width. Make sure the perches are as wide as the spring pack. If the perches
are for a larger diameter tube than the axle, then you will have to do some fill
welding. Steps: - Remove the rear axle from the vehicle. Complete removal of the
axle is not absolutely required, but makes life a lot easier. At least the D35
isn't an excessively heavy axle. This means disconnecting the E-brake and brake
lines, the driveshaft, and shocks. - Weld the new spring perches onto the axle
directly above the originals, parallel with the originals. Leave the original
spring perches in place. To prevent warping of the axle tube, make short welds
instead of one long hot bead. - Either weld the original shock mounts (which
used to sit right below the spring pack) to the lower perch of the axle or
(better) weld an alignment bolt to the shock mount. This alignment bolt will fit
into the centering hole in the original spring perch (on the underside of the
vehicle), so that when the shock mount is held tightly in place, the alignment
bolt prevents the shock mount from shifting against the spring perch. - Perform
any first-try modifications to the rear leaf pack. At minimum, you should likely
replace the bolt which holds the leaf pack together, since it does wear and can
eventually shear. - Slide the modified axle under the leaf packs. Use a jack to
force the axle up against the leaf packs. Place the XJ U-bolt plates on top of
the leaf pack, similar to how it was on the XJ. Hold the modified shock mount in
place under the axle, and use 4 grade 8 bolts to hold the assembly together. -
The original "sandwich" of parts was: axle tube lower spring perch
spring pack shock mount The new "sandwich" of parts is: XJ U-bolt
plate spring pack upper spring perch axle tube lower spring perch modified shock
mount - Tighten all the bolts up on either side. - Reassemble the brakes, bleed
the brake lines, re-attach the axle vent tube and driveshaft, put the tires back
on. - Re-tighten the bolts again under the weight of the vehicle. - Drive around
the block and re-tighten again. - After driving a few hundred miles, try to
re-tighten yet again (might as well be safe than sorry). If you get any
vibrations, you should add some shims to rotate the diff housing either up or
down. However, I know of 3 of these conversions, and none of these have required
shims. Normally, a spring over gains about 5.5 inches lift to the vehicle. This
is perfect if you want to run 33 inch tires, but a bit much if the front end
isn't lifted to match. The answer is to selectively add and remove leafs from
the rear leaf pack to provide the desired lift and ride. Since I performed a
spring over after modifying my leaf pack, it isn't possible for me to recommend
which leafs to add and remove for different ride qualities and height. What I
can do is recommend to leave the lowest, overload spring in place, but flip it
upside down. The leaf is huge! And it works great to address normal spring-over
problems like axle wrap. Notice that: - We have not relocated the rear spring
bump stops. You can if you want, but it's not really required if you leave the
heavy overload spring in the leaf pack, though upside down. You flip the spring
to allow the leaf pack to enter into a negative arc (for good up-wheel travel),
but the overload will prevent too much wheel stuffing. (Actually, I've run
without the overload, and went to full compression. 33's and even 35's will fit
into the wheel-well with only minor trimming - naturally, 35's a bit more.) - We
have not really modified the spring clips which hold the leafs together. I tried
this too, for more wheel droop (like magazines have stated). I did not notice
any more gain in wheel droop doing this. - Since the rear shock mount is still
below the axle tube, you shouldn't need longer shocks if you already had lift
shocks. My rear Rugged Trail shocks have ~11 inches travel in them, and came
with the original lift kit. Right now, they limit wheel droop, but if I had
longer travel rear shocks, the shocks would limit up wheel travel instead. So
I've stuck with the same shocks. - While the shock mount still hangs down a bit,
it is tucked up quite a bit more from the ground than when the vehicle was
spring-under-axle. Better clearance than with a spring-under. - The E-brake line
remains factory. You may, however, choose to re-route the line out of the loops
which hold them close to the frame rail. End result is really quite amazing
wheel travel without any real loss in road handling. But if the bottom leaf is
removed, axle wrap during hard offroading will be a problem over time.
Stage 3:
3/4-'Liptical
I'm extremely happy
with the spring over conversion. I'm moving on to Stage 3 only because I'm an
endless tinkerer. I can't leave well enough alone. :-) This is the current
project and still in the planning stages on my truck. It is definitely not for
the faint of heart! It will likely be performed over the next 3 months. This
involves lots of planning but promises to give even better wheel travel, again
(hopefully) without affecting ride quality significantly. Quickly, though, it
will involve: - complete relocation of shock mounts both on the axle and on the
body/frame, to give better travel and to tuck the shocks up out of the way even
more. - traction bar set-up to prevent axle wrap problems - 2 donor spring packs
- heavy modification to the frame area around the shackle mount - new spring
shackles
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Posted Oct 25 2008 11:53PM
