I know, this is a stupid question for a Jeep board but I figured I'd get your input. I have a 4cyl 91 Toyota truck with a solid axle conversion, dual tcases with 4.88s and lockers f/r 206:1 gearing 35x15.5 SXs. I am thinking of ditching the Toyota axles in favor of 66" wide wheel mount flange( WMF) to WMF Dana 60s and running 6.17 gears with 38.5" tires for rockcrawling but I do have to drive it 8.5 hrs. to Moab etc. 5.86 gears are actually the correct ratio for that size tire but I may go to 39.5s and the extra weight of the 60s will probably make 6.17s about right. Here's my question: if you guys had a 4cyl. Jeep with a manual tranny and a super low tcase, do you think that putting this size tire/axle would break other drivetrain components like the tranny/tcase? Almost everyone I've talked to so far said no, it wouldn't harm the other components as long as you beefed the driveshafts and geared the axles so the clutch wouldn't burn up driving it on the street. I appreciate your comments even if you guys say I'm a moron. I need to know one way or the other. Oh, BTW, I am not interested in Dana 44s (not much of a strength increase IMO over what I've got) or the Ford 9". I also didn't really want to go with the GM axles like the 10 bolt, 12 bolt or 14 bolt. Thanks again,
Sean

your four cyl will not haul those on the highway very well no matter the gearing, you'll be floored most of the way. for a strainght trail beater it would be ok though

that set up would give you a good mechanical advantage. the only weak spot i see could be the clutch, but the gearing should make up for that. my question is how do you plan to make 39.5s fit? your CG unless you really manipulate your sheet metal will make you a little tall for my taste. this also brings up the argument of how much do you gain over 36s with 8or9 inch diff? i see that the big tire thing has become popular with rock crawlers, but how much does this limit you in other types of terrain? food for thought

dan

I do not think this is a dumb question at all... I dont think I know the answer. However you look at it components are usually matched. There would be an immense difference in weight between the 60s and the 39.5 boggers. I think this could play havoc on your tranny. Again I dont know the answer, but think you have raised an interesting idea.

BJ

Right now I am running about 6" of lift in front and about 8" in back to clear the 35s and they rub like crazy b/c the springs are so soft. I don't mind cutting out the sheetmetal and I planned to move the front spring hangers forward 1.5" and move the axle a total of 3" forward (I already have the axle moved 1.5" forward of the stock location) and use longer f/r springs. If I have to I could drop the spring and shackle eye mounts. I'd really rather not get any taller although for a truck as tall as mine it flexes amazingly well. I've also heard I should get a couple of inches of lift out of the Dana 60 housings themselves b/c the spring pads are mounted several inches higher than the center line of my Toyota housings. BTW, the only reason I am considering such a large tire is b/c of the ground clearance issue and the fact that trails like Die Trying in Colorado are requiring at least 38's to get through without body damage from hell. I've got so much sheetmetal, it's a huge problem.

I still disagree with that requiring larger tires thing, my brother runs an 80 suzuki with the stock diffs and 30 by 11.50 swampers, he has more clearance at the diffs and better breakover angles than my elongated wheelbase flatfender. I think you would have better clearance with the stock axles and 35's you could improve the breakover angle by moving the drivetrain up slightly if needed.

I don't mean to sound like a jerk here. It's just that I don't know you or what kind of wheeling you do. Your profile says you are from Ontario, I believe. I don't think you guys have a lot of rockcrawling there; do you? Please correct me if I'm wrong. I am not trying to start anything.

The ground clearance issue is basically that to get as much clearance as I have now with 35's and Toyota axles I'd have to run 38.5s to get that same amount with Dana 60s. The axles themselves are more than strong enough to handle that size tire.

I've done most of the more popular 4 plus runs in Moab, all of the 4 plus ones here in Az and several hard ones in Colorado. I wheel with plenty of guys with Samuris and all of them run 33's as a requirement with f/r lockers and a super low range tcase gearset. Anything less can't make the trails out here.

The norm on trails for quite some time was 33" tires. Then everyone moved to 35s to do the hardcore trails. Those trails are now tame in comparison to some of the trails out there and you'll need bigger axles to handle the magnitude the trails have reached especially when running a 38" or larger tire.

BTW, I have 27" to the very bottom of my nerfs on the side of the truck. The tcase has 24" under it and it's my lowest point in the middle of the breakover area. Unfortunately, moving the drivetrain up closer to the body isn't an option. I just don't have anymore room. Ground clearance and breakover angle aren't usually too much of a problem as long as you're putting your tires on the volkswagen sized rocks. The biggest thing I want to avoid is broken axles/birfields. Putting a 35" tire up against a wall of rock and asking it to climb up with 206:1 gearing is alot to ask of an axle. That's why I'm looking into the 60s.

I hope this explains better my reasons for this question. Again, I hope I didn't offend you with anything I said. If I did, I apologize. Thanks for your time,
Sean

yes we do actually get some rock out here, unfortunatly we don't get a lot of it in one place so you get some kickass sections followed by a lot of boring road.
if you are just trying to avoid birfield breakage can't you go into one of the new birfield elim kits? or do you break enough parts to require that kind of beef? a dana 60 is a very large heavy thing and I can't picture one under a toyota.
I must however admit I've only seen the hardcore trails in pics as I havn't managed to get down there yet. also i drive a willys with seriously low gears and that may effect my viewpoint too.

I don't see the point in going to the Warn birfield eliminator kit. If I was going to go that route, I'd just put in a 44 and I don't think there is much of a strength increase there so hence, the 60s. I am flip flopping on this whole thing quite a bit. I've only managed to blow one birfield. Actually it was a Marfield. The new Marfield design is to be released soon and I'll probably go that route at least for awhile and use a weaker than the stock Aisin brand hub.

Seeing the trend of trails that max out the current 5 scale and people going to 60s f/r with 39.5" tires really got me to thinking about just biting the bullet now and getting 60s. I don't know what I'll end up doing. It is just that this sport is very addicting. You start climbing over progressively larger and larger rocks and going on harder trails. I want to be able to do any trail out there without totally thrashing my truck. I'm sure most of the rockcrawlers here on this page can relate to that.

In any case, I did talk to someone who's really pretty knowledgeable about the 60 swap. He basically said what I had thought but was hoping I was wrong. The energy has to go somewhere. If the axle/ujoints won't break (like with a 60) the tranny/tcase probably will. I could beef up my tranny to the 23 spline style as I could also do to the tcases, but then I'm spending a whole lot more money. In any case, I've got time to think about it b/c I don't have the money right now to do the swap. I really appreciate all your input though. It really got me to think about what I was planning and see that it will be an even more in depth project than I had thought initially. Thanks,
Sean

Hey Sean,
I have no idea of your budget, but how does this sound.
4.3 V6 to SM420 to NP203 front case to NP205 transfer to Dana 60 f/r. Depending on axle ratio, you will be around 150 to 180:1 with quite a bit more power.

Mark