Hello all. Long time without a post, thought I'd drop some knowledge in here. Long post warning.
Before I get into it, I spent some time with [MENTION=28464]eimkeith[/MENTION] this weekend and he's on track for another good product for the crossmember. Very meticulous product development and design.
Cliff notes and recommendations:
[MENTION=91393]papabeach[/MENTION], I'll do my best to answer some of your questions.
1. Whatever mounts you use, use the same material for the entire drivetrain (engine, transmission, transfer case).
2. Personally, I always tried to have a mount for each case. I don't know if it's required, but it seemed like a good idea to me.
3. Absolutely use the RADesign triple stick. It makes the shifter situation so much easier and requires less cutting and less loss of interior "OEMness".
4. While I love FROR/Diamond Axle, I decided not to use their case mounted crossmember. I did use their skid plate to create my current crossmember. I've seen people on other forums questioning whether or not the case bolts should be supporting the loads of the drivetrain. I chose not to risk it. I also had to add a Heli-Coil to one of those rear case bolt holes recently due to thread degradation that was preventing me from reaching torque spec. I was afraid that it would strip out completely if I tightened it any more.
5. Rock Defense is probably the easiest overall if you're willing to or planning on cutting out the factory crossmember. It gives you the option to mount multiple cases and acts as a skid plate as well. You won't have any driveshaft interference issues. You will run into issues if you plan to clock your transfer case because the built in mount platform would be useless at that point. I also don't personally like the way it attaches to the frame, but it's effective.
6. My first couple crossmembers were designed off of Bud's. Not sure if his universal crossmember is still the same. They worked well if you're willing to cut and make other modifications, including clearancing your floor.
7. The plates welded to the back of the factory crossmember seem like a good simple solution, especially if you plan to use factory mounts. It's at least a good, fast starting point. Seems easy enough to do and can be easily changed in the future to any of the other designs because it requires no modification to the frame. This is also a good solution to use the skid plates you already have.
8. I'm not sure how or why you would combine a FROR crossmember with the factory crossmember or a plate added to the factory crossmember.
9. For the mounts, any of the HD style polyurethane bushing types are pretty much the same. Pick whichever one you like best. If you go with one of these, change your engine mounts to polyurethane as well. They will allow more vibration to be transferred to the body, but I've found that any noticeable increase is normally due to something else making contact that I didn't notice or overlooked. So if you get increased vibrations make sure you check for hard parts making contact first. I've had my sliders hitting the pinch weld under the rocker panels (lots of vibration), transfer cases hitting the floor, etc. I'm pretty sure the bushing I use for the engine mounts is Energy Suspension part # 3.1108. It's a Jeep transmission mount that will bolt to the factory engine mount location. You'll need 2, and they're normally available at your local auto parts store. Here's a picture of mine in the Tacoma.
10. You shouldn't have any increased vibrations from your driveshafts. Ideally, you won't touch your driveshafts until you have your transfer cases mounted. You need to know the exact measurements. Set your pinion angle 1 degree below your driveshaft angle to account for the slight pinion rotation under load. You'll probably require adjustable upper control arms if you want to make this process exact and easy. Either way, don't accept driveline vibrations. My catastrophic failure was due to a ceased joint in my rear driveshaft. Don't let a setup error destroy your joints.
11. I have Tom Woods driveshafts and modified factory driveshafts. If you have a local shop and your driveshafts are in good shape, it's generally easier to have yours modified. It should also cost less because they won't have to provide all the joints and flanges. Hardly anyone carries the metric tube, so expect a local shop to machine your factory joints to accept a standard size tube. You'll get faster turn around from a local shop, will be able to verify fitment, and will be able to have them resolve any issues. I had Tom Woods install the flanges on the wrong side of my custom driveshaft before, which required me to mail it back for correction. I've also had a local driveshaft shop modify a factory driveshaft. When I installed it I had horrible vibrations. I took it back and they rebalanced while I waited. They also came with me on a test drive to make sure the driveshaft was causing the vibration. With all that being said, I've done plenty of business with both Tom Woods and local shops and have good experiences with both.
Most of this information will be coming from my truck build, but will transfer over to the 4Runner.
Here's the series of stages I went through with my crossmembers.
Stage 1:
Flat belly, BudBuilt Clocking Ring, BudBuilt Skid Plates.
This setup worked great. Factory vibration damping with a completely flat belly. The only thing I didn't do that I should have is sleeve the frame with tubes to prevent the frame from "collapsing" as the mounting bolts were tightened. I ran this setup for a while until I had a catastrophic failure of my rear driveshaft that took the transmission and clocking ring with it.
Stage 2:
Flat belly, Inchworm Lefty, BudBuilt Skid Plates.
After my driveshaft failure that caused a bunch of carnage, I decided to go with a Inchworm Lefty instead of another BudBuilt Clocking Ring. For this change, I just welded an extension to my crossmember and added a HD style mount. I did have to modify the mount for the clearance I required.
This also ran well and I kept it until I went with dual cases.
Of note, you have to run a clocked transfer case with both of these because when you bring the crossmember flat with the frame, the crossmember will block the front driveshaft. Clocking the transfer case raises the output flange high enough that the driveshaft will clear the crossmember. This picture shows the interference.
Here's a few pictures of the ground clearance I had while running these setups.
