401/TF727/NP208 drivetrain, 36" tires, what gears?

Sycho15 · #1 10-11-2006, 01:03 PM

I had originally planned to run 33" tires and so I had gotten 4.10 gears to go with them. Now the 4.10s have found there way into the rear of my MJ and the front of the J10 (at least, if its new owner installs them).

Now I'm planning to go SOA with GW leaves in the front and XJ leaves in the rear. I'll be running 36" tires, and 'wheeling in FL most of the time, with trips to GA and NC 2-4 times per year. I figure that with the 401, I'll have plenty of power to run 36s, with only 4.10 gears, through the mud and sand. With the automatic it might still be able to crawl up north on the rocks.

I could go with 4.27 or 4.56 gearing. I'll be running D44s front and rear. Rear will be spooled, front may get a selectable locker....

JeepnGreg · #2 10-11-2006, 01:52 PM

i'd go with 4.56 for the 36s

but thats just me

Saddle Tramp · #3 10-11-2006, 11:47 PM

Try doing the math. (Lowest transmission gear ratio) X (Low x-case gear) X (rear end gear) = Crawl Ratio. In my case, I have a T18 @ 6.32, a Dana 300 @ 2.62, and 4.56 in the pumpkins. 6.32*2.62*4.56 = 75.51 Crawl Ratio. I don’t think that there is a “perfect” number for all applications, but at least it’s a guide to compare where you started with were you would like to go.

Kriss

Jeeper99xj · #4 10-12-2006, 12:51 AM

I have 4.56's, 4.3/ 5 speed/ 231 and 36" tsl's. It's great for general trail wheeling we do in the UP (probably similar to flordia but we do have some elevation and boulders) though i think i'm going to build a doubler for the crazy rocks, i'm on and off the clutch a lot in the bigger rocks though an automatic would also solve that. 4.10's or 4.56's are probably your best bet, 4.27's would also work but are a pain to find.

#5 10-12-2006, 07:49 AM

With a manual transmission, 36" tires and 4.56 gears would mean your using the clutch more than you want....4:1 gears in the xfer case would fix that....

But running an auto would make the 208, 4.56, 36" tire a good combination for both on and off road. I think you are VERY wise in going with the larger axles for those large tires.

Is it me, or are the newer guys asking more intelligent questions lately?

z50k2 · #6 10-12-2006, 10:04 AM

If your 401 is nicely built, you can still run the 4.10's. I think if you plan to go bigger than 36's, you better consider D60's.
I am running 401/727/d300 (4:1), and 4.10's with 39.5's.
With this combination, I can't creepy crawl, but I can crawl pretty decently.
I kept the 4.10 for brute strength, the pinion is much thicker, therefore (in my opinion) should be able to take more punishment. After I was snapping 30 spline D60 shafts, I went to 35 splines, and have been lucky ( so far).

Stay with the 4.10's for now, then decide????
Ricky...seeya...

Sycho15 · #7 10-14-2006, 10:31 AM

DDawg16,
I've been around here since before you had to register to use these forums, so I'm not exactly a "new guy". I just haven't posted (here) much in a while.

z50k2,
I don't have 4.10 gears right now. I split them up to go into my MJ and the J10. I'll be buying all new gears so I can get any ratio I want.

Thanks everyone for your advice, I'll go with 4.56s.

Jeeper99xj · #8 10-14-2006, 12:47 PM

Sycho has been here for longer then me i think and i'm pretty sure he has a pretty good amount of experiance in the woods.

[ QUOTE ]
With a manual transmission, 36" tires and 4.56 gears would mean your using the clutch more than you want....4:1 gears in the xfer case would fix that....

[/ QUOTE ]

I think a 4:1 t-case would be miserable for 90% of the wheeling I do. In the woods I usually start out in Low range/ 2nd and run low range 3rd or 4th running down trails. If I had a 4:1 t-case I'm pretty sure I'd be starting out in 3rd and running 4th and 5th gears a lot on the trail. I'm hoping to adventually build a doubler to solve my low range issues.

The wheeling we do i'm guessing is pretty similar to what they have in florida though we do have some elevations and the occasional rock in the middle of the trail. There is such a thing as being geared too low. The perfect gear ratio for west coast rocks would be miserable in the midwest. We need wheel spin to make it a lot of the time.

LEVE · #9 10-14-2006, 01:27 PM

The TF727 and 4.56 gearing is well suited for the application. The auto transmission helps the rig to be a little more forgiving when those tires to grab at higher RPMs. The fluid drive and torque converter can absorb some of displaced power while not scattering drive line parts all over the trail. The 4.56 gearing should be a good upgrade. I'm assuming that wheeling in Michigan is very similar to western Washington, mud, rocks, mud, a hill or two, logs and Oh, did I mention mud? I hate mud.

Sycho15 · #10 10-15-2006, 03:16 PM

I also hate mud, but being in FL... well that's what we have most of. I have a "BoxRocks" all put together and am trying to decide what to put it in. The Box4Rocks is the front half of a NP231 converted into a crawler box. I can (and currently do) have the stock 2.72 low-range installed, or can run the 4:1 aftermarket low-ranges.

I was planning to run this in my MJ but... I may have just found someone selling a Rubicon t'case for $125 because he doesn't know what he's got. I need to see it in person to be sure. If it is, that will go in the MJ and the crawler box will go in the YJ! I might go with 4.10 gears in the YJ if it gets the crawler- that would make it a more versatile machine.

I highly recomend checking out the Box4Rocks (google it). For ~$400 and a spare NP231 you get a cheap crawler box with clocking ability.