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Five-Speed Overhaul - Jp Magazine

Pete Trasborg Brand Manager, Jp

If you don’t recall, we recently talked about how the manual transmission in our ’01 Wrangler was kaput in “ Five-Speed Overhaul, Pt. 1,” (Oct. ’12). It was hard to shift, would occasionally pop out of gear, and occasionally had no Reverse. We also discussed some of the things we tried to do to fix it before finally turning to the pros at Orange County Transmission.

154 1301 01 Five Speed Overhaul Part 2 Custom 2001 Jeep Wrangler Photo 41420777

Trasborg’s wanderlust got the better of him right after writing that article. So he then took the Jeep wheeling. A lot. After a trip over the Rubicon, to the Hammers, and the Oceano dunes, he’s settled down enough to write the second installation. So, without further ado, here are some more up-close and personal tech tips. By the way, the tranny and clutch are still doing fine even after all the on- and off-road miles. We’ll let you know in another 100,000 miles how it’s doing.

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We left off the last story right before dropping this bombshell. This is the Reverse/Fifth shift fork and rail. You can see the broken factory part on the right with the aftermarket replacement part on the left. Apparently these kinds of breakages aren’t uncommon. The aftermarket part has more material where the break occurred than the factory part and should help avoid similar breakage in the future.

The break in the fork was obvious, but a broken shift fork is often the result of a bent shift rod or other part upstream. So, OC Trans chucked our shift rods up in their lathe to check that they turned true. While we were unable to chuck it up correctly, the test shown was enough to prove that it was a bit out of true so a quick call to the parts house had us a straight one the same day.

In the past, when our input shaft tip was shot like this, we’ve either just run it or pulled apart another transmission for a new input shaft. Since NV3550s don’t exactly grow on trees, we were resigned to running the worn shaft. Then OC Trans told us they just re-tip them. The new tip is hardened similarly to a bearing race, whereas the old tip wasn’t. If we ever pull this tranny out again, the tip should look just like the “after” shot.

OC Trans went through all of the existing synchros and bushings and examined them for wear. If the old ones are worn enough, there is a possibility they might wear adjacent gears or other parts prematurely. This was our worst bushing and even it is in pretty good shape. In fact, if we didn’t have new ones on hand, OC Trans felt fine about reusing it. But we replaced them all with the new ones from the Mopar rebuild kit.

We have done a lot of flywheel and transmission swaps, but OC Trans does hundreds a year and the company is big on doing it right the first time. By using a torque wrench to install the Spec flywheel and clutch rather than an impact gun like we would have, the company never breaks or warps a flywheel. That means they never get a vehicle back in with flywheel problems.

If you have decided to try this at home, once you’ve got all the gears back together, you’ll find it nearly impossible to get the main and idler shafts into the case on your own. Time to make friends. Even with the vice specially setup to hold one shaft; the other shaft needs to be held in place by a person while someone else lowers the case onto the assembly.

Once the gears are in the rear case half and retained with the retaining bolt, it is time to mate the front case half with the rear again. There are no gaskets used to seal this transmission and this junction is always bathed in oil, so sealing it can be tricky. After some light sandpapering, lacquer thinner is used to make sure the RTV has every chance at a good seal.

Even if you aren’t rebuilding your transmission, you will want to know this. The vent for the NV3550 is right on top of the transmission. So if you get into the wet stuff frequently, you might want to change it. If you aren’t pulling the transmission, it is accessible through the inspection cover in the floor. Unscrew it and you can replace it with an NPT barb fitting to run a hose to a higher location.

We had a bit of ATF seepage under the Jeep for a while and we knew it was coming from the T-case. We didn’t worry about it too much though because like the old adage says, “You don’t have to worry about a Jeep leaking. It is when it stops leaking that you need to worry because it is out of fluid.” But since we had the T-case out, we had OC Trans change the weeping input seal.

With everything buttoned up and the RTV cured, it was time to put fluids in the cases. The NV3550 doesn’t deal well with regular GL-5 gear oil, since the high sulfur content is said to eat the synchros and bushings. So we filled the transmission with Royal Purple’s Syncromax. The T-case also benefitted from Royal Purple’s Max ATF before being slung into the Jeep.

Most of us have seen the “U”-shaped clips on the factory Jeep throw-out bearing and know how easy they are to install. Spec’s throw-out bearing has a more “S”-shaped spring that makes it much harder to install. But then, it will also be much harder for the throw-out bearing to accidentally slip off the clutch fork as well. Not that we’ve ever seen such a thing, but it can’t hurt.

Normal procedure is to use a grease to lubricate the input bearing retainer that the throwout bearing rides. The problem with doing that in a Jeep, or anything that goes off-road, is that the grease will pick up dirt and sand and transform into sandpaper. OC Trans uses Dry Graphite Lubricant that will pick up much less junk off the trail.

Five-Speed Overhaul - Jp Magazine

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