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How much cutting for 40's?

24K views 142 replies 13 participants last post by  White13JKUR 
#1 ·
Okay, so hope it's not a completely lame question in that I am somewhat prepared already.

The questions are:

How much cutting do I have to do and where? Right now I assume that I will be trimming in three spots.

1) Front fenders, aft of the front tires
2) Rear wheel well ahead of the tires
2) Rear wheel well aft of the tires

Assuming about 1.5" of trimming in the above directions is enough. Am I missing anything?

No body lift. Not gonna happen.

Here is where I am at today:
4" linear Evo coils with 3" bump stops at all four corners. 37" Nittos on beadlocks with 4" back spacing. Stock rubicon axles. Metal Cloack control arms - full set. Big bore steering box and OSC high flow steering pump. Patriot 9500UT winch.

I want to keep the same lift and bump stops.

Ordering front and rear Dana UD60s with 5.38's, 39" or 40" tires and 8 lug beadlocks with 3.5" back spacing.
 
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#2 ·
You really dont know until you flex it out. Shock length, where you have your arms set, front steering all will create adjsutments.

What are you going to do for driveshafts?1310, 1350, 1410's. What U joint does thefront dana axle use?
 
#4 ·
Yeah, I will probably take a stab at cutting and then flex it out. I'm working without a lift so it would be easier to go out and flext the jeep somewhere once it gets assembled.

The UD60s come ready to go with 1350 yokes front and rear so I'm getting new drive shafts with that. Rear one was stock and toast anyway. Front went to a 1310 a long time ago.

As the Dirtman said...………………...plus you will find more rubbing out on the trails when you really flex it out!

Stock fender flares? (Yikes!) Stock wheel well liners? You will be trimming those up.

A friend of mine just did this upgrade with Nemesis flares and liners. He has some minor rubbing on both. (4.5" springs)


You just need to keep tweaking it until nothing rubs or just live with the rubbing.
Stock fenders and flares are cut. If I hit something, it will be that metal tab poking out of the front fender wells at the top of the curve (fender supports).

I had to trim a few times behind the front tires until they stopped rubbing. Cut up the tires a lil finding out i needed to trim more. So be aggressive with the trimming from the start.
I will just trim back ~2" for now and then get it all installed.


As far as cutting, what is the best tool for a quick, precise cur on that sheet metal? I have an angled pneumatic die grinder, a handheld pneumatic sawsall thingy (old and worn out) and a Milwaukee Fuel Sawzall. Have a Dremel and hand saws too.
 
#7 ·
Dont know your shock travel or ratio but know a 1350 u joint driveshaft will not droop as much as a 1310 or 1410.

Just somehing to think about since you are dropping a ton of money.
I have been runnign 1310's on the transfer case side but 3 yolks exploded in the last 2 years I am moving to cold forged flanges at the TC. Currently my front shaft limits me on droop with 1310 at eh tc and 1350 at the axle.
 
#8 ·
Did you happend to call about fusion axles? I would take them anyday over the UD60's We just did a set on a build at Nates and they are worth the extra money. I would order them a bit wider then the UD60 with a littel more caster built into them as well. With 40x13.5 tire 70" WMS will be a better fit even with the 3.5" bs wheels or go 72" with 4.5" bs wheels.
 
#18 ·
I did upgrade to Dyna's Big Rotor kit so no problem on 37's (and probably 38's if I go that route on my next set of tires but I'm leaning towards the KM3's since I'm a BFG fan-boy)...

I agree though, 39 and up you need beef in the brake department.

...and like I mentioned, I only paid $5k for both axles so I chalk it up as a generous gift from the man upstairs...
 
#36 ·
Are you referring to the transfer case side, the axle side or both? What if I did something like 1310s at the transfer case front and rear and then 1350s at the front and rear differentials?

Your steering will be better running wider axles and wheels with less back spacing.Less stress on the wheel too but you never see any broken wheels.
I thought it was wider axle and more back spacing..??
 
#37 ·
Yep more bs, I mis spoke there. A 1310 has more misalignment then a 1350 at eaither end. It really matters on your set up and shock length/ratio. If you are running a 12" 75/25 travel shock you are likley good with a 1350.
 
#41 ·
Also Paul, keep in mind that if you do end up going the SF XD60 route and want to keep your suspension changes minimal, you'll need to run shorter springs in the rear to account for the larger tube in the rear.

I swapped to King Coils up front but am still using the AEV/Nth Degree progressive 2.5" springs from my old AEV lift and mated them to some King Adjustables.
 
#78 ·
I didnt realize you were talking about a HIGH pinion rear and neither did Eric since he mentioned regular cut gears (dont know why he didnt think it would be prudent to speak about high pinion given my question)

Doesnt that mean you will be driving on the coast side of the gear which is arguably weaker than driving on the drive side?
 
#93 ·
Ok, now I'm really interested...

2001 Dinan 330i 4-door with full size trailer hauling JKUR with FF 40s.

Where is the "this thread is useless without pics" emoji when you need it?

Our Canadian overlords are really slacking on the emoji offerings...
 
#95 · (Edited)
You guys do know that you can stuff D70 gears (with the 10.5" ring gear) in a D60 right? Carl Jantz has the set up kit.

Probably wouldn't work with a dynatrac housing though. Their casting is too tight I'd bet.


I almost started a new thread to see just how many folks are running HP in the rear these days. There seems to be quite a few.

Dynatrac and Currie are both pumping out HP rears. Somebody is buying them.
 
#96 · (Edited)
I almost started a new thread to see just how many folks are running HP in the rear these days. There seems to be quite a few.

Dynatrac and Currie are both pumping out HP rears. Somebody is buying them.
I don't see rear HPs or SF axles as necessarily bad and I still may end up with going that route.

To get a set of 44/60 axles with brake upgrades or UDS60s is going to cost about the same. You do have to buy new wheels and personally I want new tires anyway. It is easy to err on the side of a stronger axle when the price between the two choices is about equal. Selling off my current beadlocks with 37s on them will offset the cost.

What I am having trouble with at the moment is finding the wheels that I like in the correct size as well as sourcing the BFG 39s. The KM3 was only just released in the 39 size and the blue labels come through the racing group - different supply chain.


Currie is not an option right now for me because i think they are moving their factory or something and are not in production until January. Plus I have heard a few reports of local guys having wheel sensor issues on new axles.

edit:
Anyway, i now have an idea of how much cutting and where to fit 39s or 40s.
 
#98 ·
I woudl agree a 38x14.5 tire is in the 40" catagory and not sure why anyone would pick that tire over a 40 as they both take basically the same clearance tolerances.

You can get the blue lable thru normal dealers like mentioned. Nate can get them as he just got a set a couple weeks ago.
 
#100 ·
You can get the blue lable thru normal dealers like mentioned. Nate can get them as he just got a set a couple weeks ago.
Well, I would be getting the blue labels through NR4x4 and I think they are a regular tire dealer. I still think it comes through a different supply chain to the reseller. I got the impression that it is the racing division that supplies the red and blue label tires to the dealers - whether they be regular tire dealers or racing teams.
 
#101 ·
yOu can get blue lables from anyone. The red lables are resticted and only sold thru 1 or 2 distributors as well as the other non dot racing tires. Nate can get any of them but has to go thru Jackson to get them.
https://www.jacksonmotorsportsgroup.com
 
#109 · (Edited)
found em'...updated

For tire comparison..
KO2 in a 37 = 69lbs @ 36.5" width 12.5
KM3 in a 37 = 78lbs @ 36.5" width 12.5
Blue Label 37 = 79.59 lbs @ 37" width 12.5

Stt Pro 37 = 77lbs @ 36.8" width 12.5
Grapps 37 = 84.78 lbs @ 36.85" width 12.5 ----- (buy 4 get 1 free)
Toyo MT = ?? @ 36.8" width 12.5

Patagonia in a 38 = 82.4lbs @ 37.8" width 13.5 ----- (buy 4 get 1 free)

KM3 in a 39 = 87.92lbs @ 38.5" width 13.5
Blue Label 39 = 84.94 lbs @ 38.5" width 13.5


*edit*
threw in the stt pros, toyo m/t, and trail grapps also.

Seeing how the 39 KM3 is currently non-existent and if you want to take advantage of this holiday's sales, then it's pretty much Blue Labels (true 37 or 39) or say screw it and get the Patagonia's (which you'll get the 5th tire for free I believe)...

But I really want the KM3s....
 
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