American Expedition Vehicles Tummy Tucker – TJ Wrangler NON-Rubicon - Manual (Page 7)

Installation Instructions:Tummy Tucker™ – TJ Wrangler NON-Rubicon
Nth30115 v4.doc page 7 of 11 Download @ www.nthdegreemobility.com
Step 12: Final Clearance Checks and Adjustments. Now that the TT is bolted up, you can determine if
adjustments are necessary by letting the jack under the t/case output down until the full weight of the
powertrain is resting on the new isolators. The most important clearance is above and below the t-case
front output because this area moves the most under load. By viewing through the t-case drain hole at
the left-rear of the TT, observe the amount of clearance between the lowest point of the t-case and the
TT – you may use pieces of steel, etc. of known thickness to gage the gap. Due to variations between
vehicles, a few installations may need to ‘shim’ the isolators to keep the transfer case from resting or
bouncing on the TT. Several 3/8” hole x 1.5” diameter ‘fender’ washers were supplied for this purpose
and must be used in pairs on top of each isolator. If you need to add shims, you will probably have to
lower the TT skid to do this easily. You will gain a little more clearance than the thickness of washers
you add – each pair of .090” thick washers will generate about +1/8” (.125”) of additional gap.
Proper installation of your TT with a NV231 will have at least ¼” of space under the front output, and
well over 3/8” above it to the floor. If there is less than ¼” below the t/case, you need to add shims
above the isolators.
At this point you should also check for adequate clearances all the way around the transmission,
transfer case, and exhaust/catalytic converter. Generally there should be at least ¼” of space at all close
gaps between the floor or the TT and these components – if not, the appendix may provide
help/solutions.
Specific Clearance Notes:
-
’03 TJ’s with the 42RLE 4-speed auto require clearancing between the top of the bellhousing and the
floor/tunnel. There is a longitudinal rib on the top of the bellhousing that will be touching the lateral
‘pinch flange’ on the body where the dash panel (‘firewall’) meets the tunnel. The body flange can be
bent up out of the way using a long pry bar, etc. from the driver’s side – you will need to hammer the
end of the bar to move the flange out of contact.
- If you’re using a 1.25” drop TT with a body lift and motor mount lift, you will probably need about
3/16” of washer-shims above the isolators to keep the t/case from resting on the TT under the front
output. Also don’t forget to check your cooling fan’s clearance in the fan shroud (adjustments for this
are not provided with the TT – they should have come with your body lift).
- 1.25” drop TT’s generally will not fit with a motor mount lift and no body lift – the transmission
bellhousing will hit the top-front of the tunnel. It may be possible to make tunnel modifications to
allow this combination, but you are on your own!
- Flat TT’s require both a body lift and motor mount lift – see the Appendix for details.
Step 13: Final Assembly. If all static clearances are at least ¼”, you may tighten the 3/8” bolts (9/16”
head) on the top of each isolator. These can be difficult to reach, but will only have to be done once
since subsequent removal of the TT can be done at the four 5/16” flathead bolts under the isolators. The
driver’s side bolt is easiest to reach from the front of the TT (under the front driveshaft). The passenger
side bolt is usually easiest to reach from the rear (between the t-case and catalyst or sometimes over the
pipe behind the catalyst), but on manuals may be accessible from the front as well.
Step 14: Readjust Rear Axle Pinion Angle. Since all TT’s raise the t-case position relative to the chassis
for maximum clearance – your rear driveshaft angle is increased as compared to before the TT
installation – this is due to not only raising the output, but also ‘flattening’ the powertrain angle (this angle
remains close to stock if you use a drop TT with a motor mount lift.) Both your operating angle and ideal
nominal length are affected by installing a TT: the 1.25” drop TT version raises the rear output by nearly
1.5” versus stock. Generally installation of a TT does not require a longer CV driveshaft than the one
already installed. It is assumed that a proper length ‘CV’ drive shaft is already installed, but you will now
need to readjust the rear axle pinion angle higher with the TT versus with the stock skid plate. This
adjustment requires the use of an Nthº Stinger or Nth adjustable rear upper control arms (or others that
may have come with your lift kit.) Ideal pinion angle is usually about 1.5+/-0.5 degrees ‘flatter’ than the
drive shaft’s angle relative to the ground.
Once you have readjusted the pinion angle, you should measure the relative angle between the
driveshaft and the powertrain (t-case) – this is the ‘operating angle’ of the double Cardan joint. You can