Jeep Tech Questions Answered!
Low, Low, Low Range for a Flattie
I’m looking like crazy and can’t seem to find anyone who has regeared a Spicer 18 T-case. I want to go as low as I can with my low range in my ’46 CJ-2A. I think someone told me 3.8:1 is about it for super-low Spicer 18 gears. I was wondering if you knew anyone that may have done this or if you might have a lead on parts I can get my hands on. I’m hoping to regear my spare T-case and just swap it out for my current one.
I have a friend who has been running the TeraLow gears in his Dana 20 for a while. I think these are basically the same gears for a Spicer 18...if not, they appear to have a 3.15:1 kit for Spicer 18s (www.teraflex.biz/low18-overdrive.html).You are running the L-head right? If so, you could also look for a T-98 out of a CJ-5 that had the F-head. The T-98 is a predecessor to the T-18 four-speed manual and has a super-low granny First gear. T-98s for those early four-cylinders are very rare used, but do exist and with the stock bellhousing and can bolt to the back of an L-head. Herm the Overdrive Guy from ATV Manufacturing (hermtheoverdriveguy.com) is now selling a T-98 conversion kit that replaces the T-90 behind early Jeep four-cylinders with a T-98. The kit has a fully rebuilt T-98 transmission, adapters, and is designed to use most of the clutch parts and linkage from your T-90. The kit also includes parts to mount the transmission to your stock crossmember. The price of the conversion is $1650 without a core charge.
Step By StepView Photo Gallery
The Hungry YJ axle
I’ve been having an ongoing problem with my ’93 YJ. The front axle on the driver side eats axle seals all the time. I’ve replaced the seal, the axle and then the seal, and then the seal again. Now I want to know what to do next. I’ve been told that the bearings are out, the axle is bent, the housing is bent, and so on. The next trick I was told to try is to put the inner seal in and an Atlas outer seal in. Is this the best thing to do? I don’t want to get stranded, or having to crawl under to add fluid at every stop, or cause others to stop more for just me. I know where there is a CJ-5 and a CJ-7 sitting, a V-6 and V-8 model. Would either of these axles be worth a swap. Otherwise what axle would make a good swap? I live in Wisconsin where axles, motors and transmissions or transfer cases are easy to find. I’ve seen Jeeps with 30,000 miles be rusted beyond use. Any help would be great.
Jim, It sounds to me like your axle is bent, and replacement might be the easiest option for you. Unfortunately an axle from a CJ won’t work because the differential is on the other side of the Jeep (the transfer case in a CJ has a passenger-side front output on the T-case verses driver side as on your YJ). Also the bolt pattern of a CJ is different from your YJ. You’d have to swap T-cases and rework the exhaust to get the CJ parts to fit on the YJ and do something about the bolt pattern. And the only slight benefit you’d get would be locking hubs. Also the CJ-5 probably has drum brakes. Here are a few other options in increasing difficulty. If you are going for ease of replacement with no customization (welding and assembling custom parts) then you are stuck with using a stock replacement axle from a YJ. I’d look for an axle out of a ’95 YJ and make sure it has the same gearing as your current axle. Just get one from one of your local junkyards. These later YJ axles have slightly stronger axle U-joints.
If you are up to the task of a little fabrication you could build a replacement axle from a ’95-’98 Cherokee. Look for one that is a high-pinion that does not have the center axle disconnect (Most from those years should not have it). Cut the Cherokee axle brackets off and get some axle spring perches from Mountain Off Road Enterprises (PN 98102). Use these to install the non-CAD High-Pinion Dana 30 under your YJ. I basically did this in Project Ground-Up and it has worked well for about a year now.
Another alternative would be to track down a Dana 44 from an ’80-’82 Jeep Wagoneer. This axle will be a little bit stronger than a Dana 30. It also will also accept selectable locking hubs, has large rebuildable wheel bearings, large brakes (that were used on 1⁄2 ton GM trucks), and can be geared lower than a high-pinion Dana 30. You’d probably have to rebuild the axle, get new brake lines, have your driveshaft shortened, and have the axle regeared. Most of these axles have really tall (numerically low) gearing that probably won’t match your Jeep or be desirable for a lifted Jeep with larger tires. Also, this axle will have a 6-on-5 1⁄2 bolt pattern, which is different than a stock YJ (which would have a 5-on-41⁄2 bolt pattern). This means that you will need new wheels and either a set of rear bolt pattern adapters or a six-lug rear axle. Your last option to greatly increase strength, but is expensive and requires lots of customization, is to track down a Ford Dana 60 front axle. This is way overkill and should only be considered if you are gonna run big tires like 37s or larger. You could also get a new replacement axle from a company like Currie, Dynatrac, or G2 that should bolt pretty easily into your YJ. This will give you all new parts that are easy to install, but will cost more than assembling junkyard parts and then fixing them up to work for you. Hope this helps steer you in the right direction.
I have a ’79 CJ-5 with a 258 I-6, T-150 transmission and a Dana 20. I spend a lot of time driving on the interstate as well as back roads and I like to play in some mud. I was wondering what modifications and parts would I need to put an AX15 in my Jeep, or is there a better option?
I take it you are looking to bring down the RPMs on the highway? If so, the addition of a transmission with an overdrive like an AX15 or NV3550 is hypothetically possible while retaining your 258 and Dana 20. So, the parts necessary for this swap, with the use of a newer bellhousing and a transmission to transfer case adapter (from Advance Adapters www.advanceadapters.com or Novak Conversions www.novak-adapt.com), exist, but the issue for you is gonna end up being one of length and angularity of your rear driveshaft. Both the NV3550 and AX15 are about 6 or 7 inches longer than a T-150, so that means your T-case will be pushed back that far. So your rear driveshaft length and slope would be what determines if this swap is possible or impossible. The real problem is that a CJ-5 is pretty short. It’s possible that this swap could work if you could push the engine forward without the fan eating the radiator, or the rear axle backwards without the diff cover sharing space with the gas tank. Neither of those modifications will necessarily be simple, and they still may not provide the space necessary for a functional rear driveshaft with one of these five-speeds. Unfortunately, the best way to determine if this swap is possible for your Jeep involves some math and geometry. This geometric exercise depends on the slope of your transmission, the pinion angle of your rear axle, and a few different lengths. You will have to take measurements off your Jeep with the current transmission placement, and do some math, to see how long your rear driveshaft would be with the added length of the five-speed and if the angles of the rear driveshaft would allow enough travel for practical usage. To beef up for this test of geometric skill we recommend looking at the technical literature supplied to us by our friends at Tom Wood’s Custom Drive Shafts (check www.4xshaft.com/tech_slopesVSangles.html). Once you have the measurements and angles…er, slopes, the folks at Tom Wood’s Custom Drive Shafts can help you determine if you have space for this swap. They can also build you a front and rear driveshaft that will be necessary if you can fit the five-speed tranny into your CJ.
There are a few other options for dropping highway RPMs. Look for a CJ-6 or CJ-7, both of which have more wheelbase and thus more space for transmissions and driveshafts. You could also go to taller tires (which will drop your highway RPMs), or you could go to numerically lower axle gears. These last two options will make your Jeep feel less peppy on-road, but may be much simpler than undertaking a swap like this in a short Jeep.