SM420 and cross-member spacing

To set the stage - I have a CJ6 with the Dauntless, a SM420 and a D18 X-fer case. I am currently doing this conversion and are using a Novak adapter and there x-fer mount and hockey puck. It has all been bolted together and installed in the Jeep for test fit and to get proper alignment. I am wondering about the spacing between the cross-member and the frame rail. I dropped it down 1/2" and bolted it up to the frame. It fit well, looked good, but it just almost touches the bottom side of the tub. Maybe 3/16" of space. Should I drop it and gain more clearance? What spacing are you guys coming up with? I haven't seen much discussion on this part of the conversion.

Let me know your thoughts.

 

Hi Ross, I don't know the answer but since I also have an SM420, I'd like to hear some ideas. I was never happy with the engine/trans/transfer case positioning in my CJ5...

 

Ross, I'm also interested. I have a CJ6, V6, SM420 and D18. Same as you.

Post some photos. You are two steps ahead of me. I'd really like to see what your setup looks like.

I'm planning on installing a body lift. Have you considered doing that to gain some extra clearance?

Scott

 

Some people have cut out a portion of the crossmember and sat the tranny down in it to gain extra clearance.

 

Ok Joe, what are you gonna do when you install yours!!
I haven't really give it much thought on mine yet, to many other things to worry about right now.

 

Scott, I have not planned to do a body lift. I have a Skyjacker spring lift going in also. I ordered the 2 1/2" - 3" version, but it looks taller than that after getting the springs on. My body mounts are probably crushed somewhat due fatigue, age, abuse, etc. I have not addressed this issue yet. As for photos, I will try to borrow a camera for the weekend and get some shots. We are planning on stuffing it back in Sunday. I will take some side shots for body height with the rear springs on.

Joe, I am not worried about the bottom cleance so much as I am the top. I don't want it to rub on the body and make the sounds that drive ya freekin' crazy going down the rode. It seems to me the flatter those tranny/x-fer mounts sit, the less stress you have on them. You are not misaligning them when you tighen down those bolts.

Ross

 

The body lift thing is kinda out unless you are gonna reposition your pedals and steering with it.. I went that route with a sagi box and hanging pedals but I also lowered my driveline a bit ( I also have a 420) to help driveline angle due to lifting and shortening of the rear driveshaft. I made custom cross members but it sould be fairly simple to just lower the crossmember 1/2"

BUBBA

 

Well I have a 1" BL already and I'll be replacing the floorboards when I install the 420 (hopefully). If all else fails I'll make a new crossmember

 

When I put in my t18 I had to space down the crossmember a full 2 inches and it is still tight, although that was with worn out body mounts. I put in new body mounts and honestly it is not much better. Dont know if the t18 is really any taller than a 420 or not. I have seen some pics that suggest factory four speed setups used spacers, 1/4" plates stacked up between the crossmember and the frame. I used 2" square tubing, like for a receiver hitch. Even with that I had to modify the tranny cover slightly to prevent contact. Be sure to keep an eye on the bottom of the fan as you space down the crossmember, it will get closer to the radiator and depending on clearance, well you get the picture. I put in my 231 and t18 together so was able to consider best placement from both standpoints.

 

When I first put in my sm420 (V6, D18) I tried 1" spacers to lower the cross member. During the test drive I had a bad front driveshaft u-joint vibration when shifted into 4wd.
So I ended up taking the spacers out and moving the x-member up tight to the frame. Had to cut a bunch out of the floor and make a custom cover.
This always seemed backwards to me. As in you would expect less u-joint angle (lower t-case) less chance of vibration trouble. Dana 30 front end.
Just my experience.

 

I dropped mine about one inch because of the short rear driveline and using the transfercase driveline brake and a Dana 20 because I run a Dana 60 rear ( overkill ,,,,I know!!!) I also rotated the rear axle up with another degree shim to gain a better angle. I now overfill the rear end to get lube to the pinion bearing as it is tipped up slightly. With all of this the driveline shop said it would probably vibrate but could get by. I feel a very slight vibration at 45 miles an hour and then it goes away. I have done all kinds of spring flex and twisted frame off roading since then and ran it at 70 mph more than a few times with4:56s and it is still doing good!!!
I have a 1 inch body lift and plenty of trans clearance.
Dave