Question: I have an '05 Dodge Durango 4x4, and I have gone up in tire size from 30.5-inch stock tires to 34-inch new tires. I have 3.55:1 axle gears and I'm swapping to 3.92:1s to compensate. I used an online calculator to find the new gear size, so I'm good there. Do I need to replace anything other than the ring-and-pinion in this swap, or am I able to reuse the rest of the shims and bearings? How difficult is this task?
James E. Westerfield
Friendwood, TX
Answer: You're going to have to change out the front differential carrier for one that will accept the lower gears as 3.54:1/3.73:1 is the breaking point for the Dana 30 front.
The rear, I believe, is an 8.25 Chrysler and will accept the lower gearing. If you're going to do any even semi-serious four wheeling with this vehicle, I would recommend going to a much lower gear ratio than the optional factory 3.92:1 gearing. You're going to notice a real lack of performance with that tall of a tire.
I just recently did a swap from 3.73:1s and 31s to 4.10:1s and 33s on my wife's V-8 Grand Cherokee and now I sure wish I had gone to the 4.56:1 ratio as I really noticed a lack of power. I'm sure it's due partly to the added wind resistance from the higher stance and from more rolling resistance.
How difficult is this task? Well you're going to need a foot-pound torque wrench, beam-type inch/pound torque wrench, common automotive handtools, a dial indicator, a caliper or micrometer, a good service manual, and a bit of mechanical skills to accomplish the gear swap. If the gears are not set up properly, and that means perfectly, then they will quickly wear out and/or break.
Question: I have a '99 Ford diesel Super Duty 4x4 with an automatic transmission that was replaced by Ford on an earlier recall program. The replacement transmission occasionally leaks fluid-but only when the truck is in four-wheel drive! Sometimes the volume of lost fluid is so great, the transmission will start slipping. If I replace the lost fluid, normally about 5 to 6 quarts, and drive in two-wheel drive, this stops all further leakage. I can drive thousands of miles in two-wheel drive pulling heavy loads and in hot temperatures-and it never has leaked a drop.
The repair shop has suggested pulling the automatic transmission and replacing the seals on the automatic transmission fluid pump. However, I suspect the pump seals are not bad-not if the automatic transmission doesn't leak fluid in two-wheel drive.
What repairs or action would you suggest to remedy this problem? Could this be an overheating problem related to use of four-wheel drive, which puts a heavier load on the transmission and causes the fluid to be lost?
Ronald Mahan
Florence, AL
Answer: Five or six quarts is a lot of transmission fluid. The whole underside of the truck would be covered with it. My first step would be to clean the underside of the truck completely, then drive the truck in only two-wheel drive for a while just to confirm that there are no leaks, both by visual inspection of the underside and with the transmission dipstick. ATF, being red in color, stands out pretty good.
Next, find a loose-surface dirt road and drive the truck in four-wheel drive until you detect a leak and then try to trace where the leak is coming from. My guess is that there is a bad seal between the transmission and the transfer case, and the transfer case is filling up with ATF, so in four-wheel drive, the excessive fluid is being pushed out the vent tube of the transfer case.
Please let me know what you come up with-perhaps this is an ongoing problem with Ford, and in the future I will be able to help someone else with the same problem.
Question: What is the difference between a four-wheel-drive SM465 transmission and a two-wheel-drive unit? What I see, from what few pictures I can scrape up, is that there is a yoke on the end of the two-wheel-drive unit. Is there something I am missing, and if there is, what is it?
Shaun Murphy
Oshkosh, WI
Answer: I checked with Bob Hutchins of All Trans in Portland, Oregon, and he says that the output shaft is a different length and different spline count on the two-wheel-drive as compared to the four-wheel-drive version. So, if you want to hook it up to a transfer case like the NP205 or NP208, you must have the matching shaft, which can easily be changed.