Lower Differential Gears and 4 Down Towing

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Water Dog

Water Dog

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Joined
Sep 27, 2010
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Sumner, TX
Just had my differential gears changed out to 4:56 on my Jeep Wrangler from the original 3:07's. After the 33" tires went on, I found that I only used 5th gear beyond about 65mph and the power band seemed to be way off. After doing some research online, I found the 4:56 gears to be a pretty much universal recommendation for the 33's so I went with it. The gearing seems to be a lot better, although maybe just a tad low for the street (It'll probably be great for the trails). Now I'm in 5th gear at around 40mph and at 65 the tach is showing about 2500 rpm.

The question is, will this lower gearing put any extra stress on the Jeep while 4 down towing?

I haven't towed it yet with the new gears and was told I shouldn't until a break in period of about 500 miles.
 
It's still rare but some Jeeps are up in the low 5's, 5.13 for instance.  I've seen 'em towed at 65mph, even higher and wondered about overheating in the transfer case especially.  I suspect you will be fine, probably more drag than before but I'd check the temperature of the differentials and the transfer case every time you stop for a while until you know how it's behaving.  It's not exactly the same but race cars have differentials too and they run in the 10,000++ RPM zone for hours on end and sometimes blow an engine but not a differential very often.  Glad you ask about this!!  I hope we get a clear answer about the question.
 
Marc L said:
Time for 35" tires.
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maybe so?  at some point the tow bar gets even higher and higher, the CG gets higher and higher... so pretty soon you're hauling it on a trailer.  Ugh.
 
Not necessarily extra stress, but towing will turn the gears just as fast as driving. The lower gears are going to turn a lot faster at the same speed than the old set up.  So keeping the speed down while towing is a benefit as well. Also when doing maintenance remember to add the mileage towed to the miles driven to get the proper gear oil change interval. I agree with Marc about the 35" tires next time around though.

Probably more of a concern is the motor. The older motors weren't designed to spin that fast for long periods of time. My 01' Wrangler was happy at about 2000 RPM in 5th gear at highway speeds. The new JK though will run down the road all day at 3000 RPM without a hitch.
 
Hi,

Jeeps with 4:10's are standard (with your transfer case and axles) and you are only about 12% higher than that in terms of  drive shaft speed. That is not enough to cause any kind of problem. Note that much higher gear ratios are common and essentially never cause a problem.

If there is a problem at all, which I strongly doubt, its more likely to be due to a lift than the differential gearing. I'd be more worried about the U-Joints than the differential or transfer case at the slightly higher speed.

Ernie
 
If you're comfortable driving it at 65mph, and don't feel like you're over reving, you'll be OK towing it.
 
Thanks for the replies everyone. 35's...I don't see it happening  ::) ...at my age I can just barely get my leg high enough to get in with the 33's, and the dw has made it clear - "no higher"! I normally only drive the Jeep on the freeway at about 60, and when towing it, I try to stay at 55, but sometimes creep a little over that. Most of the driving I do at home is around on surface streets and I really like the way it behaves there, and am gettin' antsy to try it out on a trail.

The tow bar to the mh is level with a 2" raised receiver on the mh. I also just completed a little project I've been wanting to do since I put the after market bumper on it some time ago. Because of the way the bumper is designed there wasn't a great way to hang my front license plate without dropping my Ready Brake cable very low. I ordered a flip down license plate bracket (for a 1972 Chevy) on line and used some scrap 1/4" x 3" x 3" aluminum angle to make a bracket to hold it. Here's a couple of pics.

 

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I can just barely get my leg high enough to get in
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Well that's something I hadn't considered. I've always had problems getting out of a low vehicle but, as I think about it, I'd probably have trouble getting in a high vehicle, albeit for a different  reason.
 
Tom said:
Well that's something I hadn't considered. I've always had problems getting out of a low vehicle but, as I think about it, I'd probably have trouble getting in a high vehicle, albeit for a different  reason.
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It all works out Tom; turns out if I wasn't getting in the Jeep, I wouldn't be getting ANY exercise, save the little jobs the dw leaves me.
 
DW now has a small step stool on a cord to aid her in ingress/egress with our new 35s, but she stopped using it after a while after figuring out how to position the feet/legs.  Actually the stretching is good for our old bones I think  :).

Back on-topic - a tranny/diff shop that I used to regear us to 4.88 said to be sure and use a good synthetic oil in the transfer case.  He likes Amsoil, but Royal Purple also has a loyal following.
 
A buddy of mine has a set of electronic steps that drop down and unfold when the door is opened, and disappear when the door is closed. If I were to lift the Jeep down the road I would go that route. 
 
I tried to get the dw to use the little 2' aluminum ladder that we carry when we tow the boat (so she can get in on the boat ramp to drive the boat off the trailer), but I think her pride over-rode that and she also learned how to get in the Jeep unassisted. She refuses to relearn though. Heck, I even suggested we could hang a snatch block from the roll bar and run the winch cable through it to a little chair, and she still won't budge... ;D ;D

The differential shop I used to regear is a well known shop in our area for 4 wheelers and he didn't suggest synthetics, but it might be a good idea. Maybe I'll switch over after the break-in miles.
 
Water Dog said:
.. I even suggested we could hang a snatch block from the roll bar and run the winch cable through it to a little chair...
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Speaking of a snatch block,  I should start a new topic about this - I have one heck of a time getting the spare tire (about 90 pounds) off and on the swing-away mount tire carrier and I've been thinking about fabbing some kind of a stowable crane to lift the tire off/on the mount.
 
John Canfield said:
Speaking of a snatch block,  I should start a new topic about this - I have one heck of a time getting the spare tire (about 90 pounds) off and on the swing-away mount tire carrier and I've been thinking about fabbing some kind of a stowable crane to lift the tire off/on the mount.
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That's a great idea..! Probably wouldn't take much for 100lbs. Maybe a couple of pieces of tubing and a small boat winch. Just something that would slide into your reciever?
 
John Canfield said:
Speaking of a snatch block,  I should start a new topic about this - I have one heck of a time getting the spare tire (about 90 pounds) off and on the swing-away mount tire carrier and I've been thinking about fabbing some kind of a stowable crane to lift the tire off/on the mount.
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John, you could switch to a tire carrier like this:
http://www.youtube.com/watch?v=0jfpVmFA-yc
 
To a Nissan guy, a Jeep is a Jeep.  Kidding aside, I know the difference, I had a '95 YJ, only series with square headlamps (like or hate).  Also the first Dodge model.  I miss AMC.
 
I never 4 down tow my Jeep. It wears out the tires ( I have 37") and wears out the suspension and ball joints. When you start to modify your Jeep it is time to trailer it. That is just my opinion.
 
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