Front diff and tires >31"

RespectMyLibertay · **Posted:** Mon Feb 11, 2008 3:25 am

I was thinking of eventually going with JBA's 4" lift, or doing a SFA-swap, probably leaf-sprung just for kicks and cost.
Until then, I was thinking of buying 1.5" spacers front and rear, JBA's custom CV axles, extended SS brakelines, and 4" struts and shocks (would I even need the struts?), still easily totalling over a $1k.
With those mods I'd want to run probably 32" tires max, which could maybe have a true OD closer to 33". The only problem I see with this whole set-up would be the front diff and possibly the steering rack angles. What could I do to prevent my diff from exploding other than getting a collar to put around shaft input? That whole deal just makes me want to go SFA unless it can truely be prevented. Sometimes tires just have to be spun if you have open diffs, right?..so I see that as a problem...unless a locker, like say an ARB, can help prevent the possibility of that happening? People only explode their D30a with open diffs and one front tire spinning, right? I'd get an ARB up front just to prevent the grenading. The awesome offroad capability would only come second to preventing the diff explosion, if it indeed can.
Eventually, after running the spacers for awhile and saving money, I'd buy the full 4" lifted coils from JBA, essentially buying his 4" lift in pieces, but this is all assuming the front diff problem can be solved/prevented. And what about the rack, specifically the out tie rods? I read awhile back that it could be a problem when going higher than 2.5" (my outer tie-rods already look kinda adverse from my 2.5" lift) Thoughts? I only brought this up because the front diff problem is ridiculous and if there is no solid solution, then I'm saving for a SFA-swap immediately. As I remember, people have used the collars, but I have not read anything about them doing their job handling the stresses of the tires that people are going to be using with 4" and higher lifts. This is not to say that the collars can't hold back the forces of bigger tires...I just don't know myself (I don't have a diff collar currently). I do know the current average LOST KJ has 245/75R16s, which is humbly called a 31. The tires I'd want to put on my 4" lifted KJ would probably be a Swamper of 60 pounds, and then I'd probably have steel rims. My current tires weight 45 lbs each, but they are also on lighter aluminum rims. Is this difference in tire weight and therefore force (on the diff input and on the steering rack components possibly) enough to keep us from running >32" tires when we start running >2.5" lifts?
Thoughts?

jeepkj02 · **Posted:** Mon Feb 11, 2008 11:06 am

A SFA can cost between $10-20K. The JBA is $2-3K, but even with the JBA your still stuck with the aluminum diff, no way around that. Not sure if it can take the weight of a 33" swamper and steel wheels without eventually exploding, even with a collar and locker/lsd.

Your frankenlift is a great lift, play around a while with it and save up for a SFA, or get another trail rig ($2-5K) and a lift, tires and lockers ($5-7K). Which would be the same cost of doing a SFA to the KJ. Hmmmm.....tough decision.

KJ04 · **Posted:** Mon Feb 11, 2008 11:33 am

RespectMyLibertay wrote:

I was thinking of eventually going with JBA's 4" lift, or doing a SFA-swap, probably leaf-sprung just for kicks and cost.
Until then, I was thinking of buying 1.5" spacers front and rear, JBA's custom CV axles, extended SS brakelines, and 4" struts and shocks (would I even need the struts?), still easily totalling over a $1k.
With those mods I'd want to run probably 32" tires max, which could maybe have a true OD closer to 33". The only problem I see with this whole set-up would be the front diff and possibly the steering rack angles. What could I do to prevent my diff from exploding other than getting a collar to put around shaft input? That whole deal just makes me want to go SFA unless it can truely be prevented. Sometimes tires just have to be spun if you have open diffs, right?..so I see that as a problem...unless a locker, like say an ARB, can help prevent the possibility of that happening? People only explode their D30a with open diffs and one front tire spinning, right? I'd get an ARB up front just to prevent the grenading. The awesome offroad capability would only come second to preventing the diff explosion, if it indeed can.
Eventually, after running the spacers for awhile and saving money, I'd buy the full 4" lifted coils from JBA, essentially buying his 4" lift in pieces, but this is all assuming the front diff problem can be solved/prevented. And what about the rack, specifically the out tie rods? I read awhile back that it could be a problem when going higher than 2.5" (my outer tie-rods already look kinda adverse from my 2.5" lift) Thoughts? I only brought this up because the front diff problem is ridiculous and if there is no solid solution, then I'm saving for a SFA-swap immediately. As I remember, people have used the collars, but I have not read anything about them doing their job handling the stresses of the tires that people are going to be using with 4" and higher lifts. This is not to say that the collars can't hold back the forces of bigger tires...I just don't know myself (I don't have a diff collar currently). I do know the current average LOST KJ has 245/75R16s, which is humbly called a 31. The tires I'd want to put on my 4" lifted KJ would probably be a Swamper of 60 pounds, and then I'd probably have steel rims. My current tires weight 45 lbs each, but they are also on lighter aluminum rims. Is this difference in tire weight and therefore force (on the diff input and on the steering rack components possibly) enough to keep us from running >32" tires when we start running >2.5" lifts?
Thoughts?

Considering all the drawbacks of the D-30A and IFS, the answer should be quite simple.... SFA!

RespectMyLibertay · **Posted:** Mon Feb 11, 2008 3:17 pm

Well that's enough for me! I'm saving for a SFA-swap, but I'm not doing any $10K deal. Ask the first guy who did it himself, Jedi something...he definitely didn't spend no $10K and he still had coils front and rear. I plan on pulling the leafs and axle from a pull-and-save, definitely no more than $500 total. I'll probably get JBA's rear 6" lift components and a new driveshaft with a SYE and call the rear good; I'm guessing that'll be no more than $1.5K. I want to do it all myself with help from my welder friends for under $5K (not including lockers and new tires/rims). 33" tires is good enough for me, as long as I can get still get some good flex. Give me 2 years to save $ and compile components and on the 3rd year I bet I'm gonna have a SFA underneath the front of the Lib.

KJ04 · **Posted:** Mon Feb 11, 2008 9:12 pm

RespectMyLibertay wrote:

Well that's enough for me! I'm saving for a SFA-swap, but I'm not doing any $10K deal. Ask the first guy who did it himself, Jedi something...he definitely didn't spend no $10K and he still had coils front and rear. I plan on pulling the leafs and axle from a pull-and-save, definitely no more than $500 total. I'll probably get JBA's rear 6" lift components and a new driveshaft with a SYE and call the rear good; I'm guessing that'll be no more than $1.5K. I want to do it all myself with help from my welder friends for under $5K (not including lockers and new tires/rims). 33" tires is good enough for me, as long as I can get still get some good flex. Give me 2 years to save $ and compile components and on the 3rd year I bet I'm gonna have a SFA underneath the front of the Lib.

Sounds like a plan, and good luck with it. Don't forget new 4:56 gears for those 33's.

jeepkj02 · **Posted:** Mon Feb 11, 2008 9:25 pm

All this talk on SAS is making me want to do one myself. :twisted:

Good luck on the SFA. Make sure you know what your getting yourself into. There is going to be a lot of fab work in the front, definitely not a easy job.

RespectMyLibertay · **Posted:** Tue Feb 12, 2008 4:39 pm

Don't worry, I definitely took gears into account (My KJ is a dog on the highway with my 31s and 3.73s).
I was hoping to simplify things by going leaf-sprung up front, but we'll see. I'm not 100% sure when things will get rolling, but I'm going to consult many other Jeepers personally before I actually start compiling parts and looking at what I'm going to do. I know steering is probably going to be the hardest part, except for maybe putting the spring mounts into place (might need to fab a new front bumper). I haven't really done research, but I do remember Marty (Rock Lizard) once posted on this board about doing a budget SFA-swap and going leaf-sprung. That was my inspiration...I'll have to dig up that post.

KJ04 · **Posted:** Tue Feb 12, 2008 5:03 pm

Check out the SFA section to what people have done do far.

Front diff and tires >31"

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