Gearing Options

[ApexOffRoad]

Guys,

I have a 99 Tj with 4.6 Golen, 32RH Auto, 4.3 Atlas and Dynatrac 60/Pro Rock 44 with 4:10 gears/air lockers. Was running 35" tires but going to 37"s. Wheeling preferences have changed and I'm now looking for a better crawl ratio with the larger tires. This setup was fine for smaller tires and easier trails but simply geared too high for what I want to do now. Common sense would suggest that I simply re-gear the axles but of course it can never be that simple.

What I really want is to swap to an NV4500 manual. I know that makes some of you 32RH fans cringe. I have also read on this forum that this swap can be challenging with electronic issues as well and mechanical and trans tunnel modifications. I'm after the gears and especially the versatility of the ratios in an NV4500 for both on road and off road use of this jeep. Granny low in the NV4500 with 37" tires and my current setup would produce a crawl ratio of 100 without re-gearing axles (I have 66 now with the 32RH and 35's). With 4:10 gears in 2 wheel drive, additional gears forward and 270hp the Novak guide puts me at freeway speeds of 70 mph at 2700 RPM's...Sort of the best of both worlds for my needs.

Here is the real question for you guys. It know it makes a heck of a lot more sense to keep the 32RH, re-gear and just live with a lower top end on the open road. I like the automatic enough to keep it but there is one additional inherent problem that I think a lot of TJ guys deal with. It kinda sucks and is causing me to consider this swap. When locked in 4 low with the 32RH the TJ wants to power right through the brakes, when you add lockers the brakes almost become irrelevant (I have 4 wheel disc setup). I've posted brake issues on this forum before with good suggestions from members that have helped with this problem, but it's still an issue. I've also become pretty good at cycling between neutral and drive with this rig when wheeling just to save my brakes but it's a nuisance and takes away from the enjoyment. I played around with the idea of a modified torque converter but have only read mixed reviews on the subject with cons outweighing the pros. Not sure if I have left out any options which is why I decided to post here. Appreciate any insights you guys might have.

 

[Jerry Bransford]

Your 1st crawl ratio with any automatic is infinitely higher with its torque converter. That's because the torque converter makes its 1st gear ratio infinitely low. Pay no attention to the raw 1st gear ratio number of an automatic, its torque converter makes it misleading and irrelevant.

Not to mention an automatic's torque converter does a magical thing called torque multiplication. That gives 2-3X greater low-end torque like when trying to get up and over a climb or obstacle. True, look it up.

 

[Steel City 06]

Personally, I would ditch the Atlas II and install an Atlas IV before going to a NV4500. It would be difficult with the rear driveshaft, but then you get your crawl ratio (11.72:1 instead of 4.3:1) and still keep a usable transmission. Not only that, but you would have a large number of different ratios to play with, and you still have a torque converter.

I wonder if it is possible to retrofit a 42RLE into a 32RH spot. Then you could regear to 5.38 (or deeper, if your axles allow) and still have usable freeway speeds.

Certainly you could retrofit an AX-15 to get an overdrive gear, which would allow you to gear axles ~20% deeper. A TJ NSG370 has a bit wider ratio spread, but not by far.

As for the brakes, if you need the brakes to hold the Jeep in low range and 1st, you may need both a big brake kit and hydroboost brakes. The big brake kit provides more leverage and surface area, and the hydroboost provides higher pressures and adequate fluid displacement.

 

[freedom_in_4low]

I'm with Jerry on this, crawl ratio is totally different between auto and manual. Even with the low 1st of the 4500 you'll probably find that your crawl speed ends up worse off.

have you considered swapping in an auto with 4 speeds like the AW4?

I personally waffle about the auto vs manual conundrum for my next rig. I like the idea of a torque converter helping with low end torque and crawl speed but if I get into trouble the clutch is a much quicker ripcord to pull than shifting an auto into neutral and the rig I want to get only came with a 6 speed or a 42RLE, and the ridiculous OD ratio of the auto would require yet another regear.

 

[Duck Doctor]

I have one rig with the 4.3:1 geared Atlas with AX15 and another rig with the 42rle and Rubicrawler under drive. The automatic transmission rig was way too high geared for rockcrawling even with 5.38 gearing. Spent the entire day riding the brakes in 4-low until I installed the Rubicrawler.

Like your idea of going to a manual with granny low first. I plan to do the same with my Atlas equipped rig but going for a 4 speed instead.

 

[Lou]

Not sure how your jeep is set up, but getting an nv4500 to fit is going to take a lot of work and effect belly height for sure. Adding an atlas 4 to a tj is probably not going to work either.

 

[Jerry Bransford]

have you considered swapping in an auto with 4 speeds like the AW4?

The AW4 is no longer the popular swap it was for a while due to it requiring more power to operate, it's longer so it needs a shorter driveshaft, and that it runs significantly hotter than other automatics like the 32RH.

 

[ApexOffRoad]

Jerry, I don't doubt that you know what you're talking about and thanks for responding. That still doesn't solve my issue of powering through the brakes with my current setup. I think my problem does relate to the axle/trans gearing because low lock is just too fast over the rocks. It prompts the knee jerk reaction to brake and slow down the crawl or constantly shift into neutral to apply the brakes without fighting the driveline. I drove a CJ last month over the Rubicon trail with an NV4500 (thats where most of this originated). After jockeying around with my automatic in and out of gear it was refreshing to simply engage a lower (locked in) crawl ratio to suit the terrain and shift accordingly to slow or speed up the crawl. I also noticed that locking in the lowest gear performed a little better when getting up steep obstacles compared to the setup in my TJ. At least in my rig, the automatic torque converter tends to slowly build rpm's and on occasion would break loose the tires even with a light touch on the gas pedal and even more noticeable on a grade with loose gravel. That's why I asked about available torque converter mods and if they make sense or if they would make the problem worse. Again I like the automatic, just hate the braking issue and constantly standing on the brakes to stop or slow the crawl. I realize I'm probably avoiding the same problem in a manual by simply depressing the clutch instead of shifting into neutral in the automatic so maybe it's just my preference. All you have to do is throw the automatic into reverse a couple times on accident to get frustrated where a clutch in a manual is just more routine. I don't want to give up my top end performance either so maybe I'm kidding myself that there is a win/win here.

 

[Steel City 06]

Jerry, I don't doubt that you know what you're talking about and thanks for responding. That still doesn't solve my issue of powering through the brakes with my current setup. I think my problem does relate to the axle/trans gearing because low lock is just too fast over the rocks. It prompts the knee jerk reaction to brake and slow down the crawl or constantly shift into neutral to apply the brakes without fighting the driveline. I drove a CJ last month over the Rubicon trail with an NV4500 (thats where most of this originated). After jockeying around with my automatic in and out of gear it was refreshing to simply engage a lower (locked in) crawl ratio to suit the terrain and shift accordingly to slow or speed up the crawl. I also noticed that locking in the lowest gear performed a little better when getting up steep obstacles compared to the setup in my TJ. At least in my rig, the automatic torque converter tends to slowly build rpm's and on occasion would break loose the tires even with a light touch on the gas pedal and even more noticeable on a grade with loose gravel. That's why I asked about available torque converter mods and if they make sense or if they would make the problem worse. Again I like the automatic, just hate the braking issue and constantly standing on the brakes to stop or slow the crawl. I realize I'm probably avoiding the same problem in a manual by simply depressing the clutch instead of shifting into neutral in the automatic so maybe it's just my preference. All you have to do is throw the automatic into reverse a couple times on accident to get frustrated where a clutch in a manual is just more routine. I don't want to give up my top end performance either so maybe I'm kidding myself that there is a win/win here.

If all you’re trying to do is make it easier to stop, why not combine a big brake kit and hydroboost? They could both be installed in a weekend and are fully reversible. It would also be much less expensive than a whole new transmission and all the necessary auxiliaries.

If nothing else, consider the hydroboost.

 

[Steel City 06]

http://www.vancopbs.com/product_p/6.htmhttp://www.vancopbs.com/product_p/2003j.htm

 

[ApexOffRoad]

I don't really like the other manual options for this TJ the way everything else is set up. I have an AX15 in my YJ and I really like it but the gear ratio's aren't as low as the NV and I don't want to swap tranny's and still have to re-gear to run larger tires. I busted the Atlas rear output yoke on this jeep last month and damaged the driveshaft so good a time as any to swap transmissions and modify driveshafts. The long arm setup I have with 37's should make up for reduced belly height. Spoke with Advanced Adaptors and others, they claim the swap isn't as hard as it seems but I'm taking that with a grain of salt. All said and done sounds like a stupid amount of money so once again maybe the smart move is just to re-gear axles and live with 32RH?

 

[ApexOffRoad]

Good advice from all...thank you. Lots to consider.

 

[ApexOffRoad]

Update...

I went with the hydroboost and big brake setup and upgraded to 37" tires. Kept the 4:10 gears with the 3 speed auto and couldn't be happier with the "on-road" performance. The 3 speed trans with 4:10 axles and 37" tires is great on the road. The Golen 6 has plenty of power to push those larger tires up a grade. So much so that I would consider driving (not trailering) this rig for a distance. I played around with it on some loose hillsides and the crawl ratio also still seems to be acceptable with the larger tires. What a difference in the braking!...stops on a dime and locked in 4 low does not power through the brakes. On paper and even with the Atlas the gear ratios for even a moderate trail don't look good. But as Jerry said the torque converter does somewhat compensate for the higher gearing. Running some harder trails in July, might have a totally different opinion after that. Probably have to re-gear to complete the the upgrade to larger tires...or just get labeled as a mall crawler