I really like the Savvy skid plate setup. Unfortunately, the good folks at Savvy don’t make a crossmember that fits the 32RH three-speed auto transmission in my 99 TJ (Not yet).
So… with some basic engineering and fabrication skills on hand, I set out to build my own custom crossmember for the Savvy skid. The design is based around AEV’s vibration isolation kit, which AEV was nice enough to sell it to me by itself along with all of their tummy tucker hardware. I mounted this on a piece of 1/4" plate.
Before I could size the support cross section, I needed to find out how much transmission dead load the crossmember would be supporting. I went about this by getting creative with a large bathroom scale.
The scale reads 225 lbs, but this includes the weight of the support blocks. However this does not include the additional weight of the removed drive shafts. As a conservative measure, I go ahead and design for 250 lbs.
On the AEV tummy tucker, the bottom of the low profile isolation pads are about an inch below the frame rails without the use of a body lift. I figured I can locate the isolation pads level with the bottom of the rails with a 1.25" body lift. Taking a straight edge along the top of the Savvy aluminum skid, I see I have about 1.25" inches for a crossmember section depth.
Time for a preliminary check of clearances… With the 1.25" inches of spacers under the isolation pads (0.25" plate + 2 x 0.5” wood boards), I jack up the Savvy skid onto the frame rails.
Last edited by Sahara Surfer; 08-27-2013 at 01:26 PM..
Reason: Wrong transmission type called out.
Short of doing computer simulation, I made a lot of conservative assumptions and simplified the problem to a box beam with pined connections at both ends with a maximum stress under the highest load under one of the isolation pads. I checked this bending stress against a fraction of the yield strength of the material per the AISC steel design manual.
Enough of the nerd talk , here is the fab work. I started out by cutting a 2 x 3 x 3/16 rectangular tube in half and laying sections of them on the Savvy skid:
The center section has to have access holes to tighten the bolts on the isolation pads. I reinforce those areas with ¼" thick tube to transfer the stresses. Note the interior reinforcement plate at the end. The bottom side will have internal plate reinforcement at the joints.
Assembled center section
You can follow the progression. I have marked the location of the center section on the Savvy skid and use it as a reference guide. Note that the transmission mount is not centered. Also, I welded the ½" bolt sleeves made from ¼" thick tubes. These will tie in to padeyes welded to the 2 x 3 angles shown on the photo below. The angles will be fillet welded to the insides of the frame.
Good work. I took a different approach. A buddy of mine who has done quite a bit work on my jeep, built a custom trans mount bracket and did some work on the Savvy cross member. Love the way it performs.
I finally finished my SYE install. It took me all day... If there was ever any doubt, lock rings are the devil. I finally got frustrated with the blasted things and in a fit of rage, I took at cut wheel to the OEM output housing. Good thing JB conversions gives you all new hardware at the output shaft.
Anyhow, that is done and I can install the new crossmember. Here is a view from the rear. Still clears the tub.
A view of the front side:
Another view of the back. That low profile cat kicks ar$$e!
Profile shot. All it needs is the Savvy skid.
I ran out of time and will have to test fit the skid later, my daughter is giving me dirty looks because Jeep time is cutting into daughter time. I still need to refill my transfer case with ATF, tighten some bolts on the cable linkages, and attach my front drive shaft. I love how I can now access this area while keeping everything supported.