November 2009 4x4 Truck Repair Questions - Tech LinePosted in How To: Tech Qa on November 1, 2009
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Grand Cherokee Axle Options
Question: I bought a 1996 Grand Cherokee ZJ recently. It was built at the very end of 1995, according to the door sticker. It has stock Dana 30/35 axles with 3.55:1 gears. I put a small lift kit and 31-inch tires on it, and now I want to re-gear to 4.11:1 or 4.56:1 to help out the tired 4.0L Six. The problem is that apparently Jeep changed the D30 axle halfway through the 1996 model year, judging from what I've read, so the early '96 ZJs have a "CJ-style" ring and pinion, and the later 1996 models have a "TJ-style" ring and pinion. I've also been told that to go from 3.55:1s to 4.11:1s on my early 1996 ZJ D30; I'll have to get a new carrier as well as different bearings and the like. In other words, it's going to be a mess and far more complicated than just ordering up a ring and pinion. Can you verify if this is true? Any advice for me? The D35 out back shouldn't be as problematic.
Answer: There are three versions of the Dana 30 ring and pinion that I know of. Some reference books say that Jeep went to the short-pinion design in 1997 1/2, and some say '98; the one I looked at (and order my gears from) said the change wasn't made until '99, and only in the WJ model. The gear Jeep technician I talked with says that they came each way in the '98 ZJs. Actually, the ring gear is likely the same, but the pinion shaft is shorter. Naturally you have to buy matched sets. The differential bearings are the same, but the pinion bearing is different.
The other two designs are the standard and the high pinion, and I have never seen or even heard of a ZJ with a factory high pinion such as those that were used in most of the XJs. Fact is, all the ZJs from '93 to '98 used the same basic frontend. While the axle tubes and steering knuckles are different between the CJ and the ZJ, the ring and pinion are the same, with the exception of those few short pinion housings used in the ZJ. In fact, this same ring and pinion fits a lot of different vehicles that use the Dana 30 housing.
Yep, it doesn't make any difference what style of a 30 you're using, you will need to change the carrier to match the gear choice due to gear thickness and spacing. The bearings are all the same, but it's not a bad idea to plan on putting in new bearings when replacing a ring and pinion, especially one with high mileage.
Yes, the rear is pretty straightforward. The 1993-1998 model years all appear to have used the same Dana 35 rear axle. There were some models that used the Dana 44 rearend, which had an aluminum center section and a different-than-standard gear set. Either way, you will also need to change the carrier. The shafts are held in with what's called "C"-clips. If you should break an axle shaft, the wheel and broken axle shaft will part company with the vehicle. Oh, and it's a pretty common event, especially with larger-than-stock tires.
You might want to rethink your plans and swap out the axle. There are aftermarket axle shafts available, or you could swap the complete rearend out for something stronger. One thing that you don't want is a Dana 44 from another Grand. There is little to no aftermarket support for these axles, and gear choice is limited and expensive. An axle swap is not a cheap alternative, but it's pretty common to put a Ford Explorer rear in the Grand. I suggest you Google something like "8.8 Ford in Grand Cherokee," and also check out our "Project Ain't It Grand-er" at fourwheeler.com. You might be interested in some of the changes we made to our Grand Cherokee, including a front and rearend swap.
Wants To Graft Wagoneer Axles To CJ
Question: I have a 1985 CJ-7 that has a Dana 35 front axle and an AMC 20 rear axle; both are wide-track units. I was looking to install Dana 44s. Would a set of Dana 44s from a 1990 Jeep Grand Wagoneer work? Would they bolt in, or will major alterations be needed?
Answer: Well, you could, but it sure would be a lot of work. First off, if you look closely, you'll see that the 1990 Grand Wagoneer also has an AMC rear axle. Nice thing about this one is that it is a flanged axle style, not the two-piece tapered axleshaft/hub assembly like what's under your CJ. Plus, I have been told that the tubes are thicker-wall pieces. However, the bad part is that while the front end is a Dana 44, the differential is on the right side (passenger side) not on the left (driver's side) like your CJ-7. This means you either re-tube the axle and move the differential over to the left side, or find a transfer case that will bolt up to your present transmission, like the one that was in the Wagoneer.
Rx For Tired Chevy Rear Springs
Question: I own a '98 Chevy Tahoe 4x4 four-door with the 5.7L Vortec V-8 and 3.73:1 rearend. I tow a 4,900-pound camper three times a summer. Problem is my rear suspension is gettin' pretty tired-the leaf springs are worn out and need new shocks. What is your advice: A new set of springs with air-adjustables? Add-a-leaves? Something else? The truck has 115,300 miles on it. I can't get a reasonable answer here in town!
Answer: I've had good luck using the air support bags from Air Lift (www.airliftcompany.com/). They're fully adjustable, allowing you to tune your suspension under all loads and road conditions. Just add air when towing or hauling, and then remove air for a softer ride when unloaded. Most likely, you can then keep your present springs right where they are
Mating NP208 To 700R4
Question: I have a Chevy Crew Cab dually that I am transforming. I will be using a 454 engine and 700R4 transmission. Or do you think I would be better off with a TH350 or TH400 transmission? I was thinking the overdrive might give me one or two more miles per gallon.
I think I am going with the NP208 case because I have about four of them. Will any work with the transmission if they were mated to a standard tranny, or will it take a certain one? Maybe an adapter? I have not tried to match them up yet due to the fact that I'm waiting on the transmission to get to me.
Answer: I think that the 700R4 would be fine if rebuilt properly. The advantage is the Overdrive gear and a lower First gear. If you plan on really beating on your truck, or making lots of horsepower in the future, then go with the 400.
I would pass on the NP208, as most likely you will go through all four of them with breakage problems. Again, it all depends on the amount of power your big-block makes and how you treat the truck. I suggest you find a salvage yard that will trade you the four 208s for an NP205. There were a lot of different spline input gears used in the 205 transfer case, and even two different bolt patterns. Most likely, you will need an adapter. Before you buy or trade for the 205, I suggest that you contact Advance Adapters (800/350-2223, www.advanceadapters.com) and discuss which transfer case and adapter you will need.
Tech Letter Of The Month
Ring Gear/Flywheel Cooking Tips
Question: I have a Suzuki Samurai that I have poured hours into and now have a capable and fairly reliable rig. However, after a weekend of muddin' around in ponds and such, my starter solenoid got stuck and fried my starter, and I somehow damaged the ring gear. I had a new starter put on, but sometimes it misses and grinds on the ring gear. I have heard from several people that it is possible to flip the ring gear and it will work like a new one. Is this possible? If it is, will it work with my car?
The transfer case on my Samurai has too high of a low-range to wheel with 32s so I would like to get some reduction in low range. Are there any kits or low-range boxes I could buy to reduce my gearing?
Answer: As to the ring gear on the flywheel: yes, it can be replaced, or you can take it off and reinstall it in the opposite direction. Getting one off without getting it out of round is kind of a pain. I would really suggest that you just buy a new one.
To get the old one off, drill a hole in it and then strike the hole with a chisel. This should cause it to split and fall off. Put the flywheel in the freezer for a few hours. Take the new starter ring and stick it in the oven on high. When the ring is really hot, then carefully lay the flywheel on a flat surface and drop the ring on the flywheel. Tap it all the way around with a big hammer until it is completely seated. You only get one chance at doing this, so it's advisable to practice going through the motions a couple of times before doing it for real. I am not sure where you could find a new ring gear but a reconditioned flywheel with a ring gear can be had from BAP Import Parts (www.bapimportparts.com) for about $40.
Yep, those little four-cylinder engines just don't like bigger tires. Transfer case gearing is the way to go. Poly Performance (www.polyperformance.com) has a new set of gears for your transfer case. Low range reduction is 6.5:1, while high range is 1.7:1. These gears are strong, they run quiet, and they take a huge amount of abuse. This complete kit includes four new cut gears, countershaft, needle bearings, shims, O-ring, gaskets, and input/output seals. While the price of about $500 seems high, it's really pretty low when you consider what you're getting. The 20-percent lower high-range gearing is also a nice addition for those pesky highway grades, especially in the future if you plan on going to an even taller tire.
Another source for Suzuki driveline parts is a place called Asian Auto Parts of Arizona (www.asianautopartsofaz.com/). They sell a similar 6.5:1 low-range kit, as well as one that's a 4.9:1 low range, and another with a 4:1 low-range. Plus, they have a lot of driveline parts as well as some nice engine parts when you decide you need a little bit more power out of that little four-cylinder