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04moneypit 01-15-2006 02:26 PM

04 wrangler tranny problem
Hi all, I'm a pretty competent mechanic, but never experienced this problem before. I have a 2004 TJ with a 4.0 L NV3550 trans, np231j transfercase with a JB conversions SYE, tom woods driveshaft, rotated my D35 housing up for the CV driveshaft, detroit locker in back with 4.11 gears, D30 front with a detroit truetrac and 4.10 gears, a 4" rough country suspension lift and 33x12.5x15 bfg all terrains. I have done all the mechanical upgrades except install the gears and lockers (didn't have a housing spreader or bearing press). Got the jepp back from the shop after the gear install and noticed my trans was hard to get in gear, grinding when I try to shift too fast, but if I wait a few seconds, it goes in fine. Only has 19500 miles on it. Seems like the master or slave cylinder is bad and causing the clutch not to engage properly, like it's slow? Or thought it could be the synchros, but it didn't have this problem before it had been to the shop, or I didn't notice it, which is pretty improbable since it is my daily driver. So what do you guys think?:confused:

quadna71 01-16-2006 06:13 AM

my 3550 got replaced at 35k for the synchros being shot in 2nd and 3rd. it had been doing it since 12k...but i wanted to wait until almost at the end of the 36/36 warranty. the dealer swapped it out and i was good to go after that. only at 39.5k now so not sure about longevity.

p.s. do you have a body lift? slight changes to the angle of the shifter will put side pressure on the shifter handle and can accelerate wear on the synchros.

04moneypit 01-16-2006 07:27 AM

No, no body lift (think those are worthless myself) but I did have a transfer case lowering kit on it for a couple weeks, and it would pop out of reverse. But I only ran it for maybe 150 miles until I got my SYE kit and cv driveshaft. This problem didn't surface until just now.

Jerry Bransford 01-16-2006 11:57 AM

To the best of my knowledge, it's verly likely your Detroit Locker causing the gear grinding. The additional backlash from the Detroit Locker does something I don't understand to degrade how the synchros inside the transmission operate. I observed the same issue with my '97 after upgrading to a rear D44 and Detroit Locker, even though it uses the AX-15 transmission.

04moneypit 01-16-2006 12:57 PM

Well, thanks for the input, but the real question is, how could the rear end cause a trans problem?

Jerry Bransford 01-16-2006 05:32 PM


Originally Posted by 04moneypit
Well, thanks for the input, but the real question is, how could the rear end cause a trans problem?

I mentioned this above... that the added backlash in the Detroit Locker screws up the operation of the synchros inside the transmission.

04moneypit 01-18-2006 10:16 AM

Took it to the dealership since it should still be under warranty, they said it was my 2-3 synchros and my idler input shaft. In human speak- the trans is F#@!*d so he had to call his supervisor to see if they'll warranty it. Hopefully so.

Jerry Bransford 01-18-2006 01:25 PM

Don't forget that your gear grinding occurred after the upgrades which included the Detroit Locker which I believe is the likely root cause of the problems with the synchros. Once again, the backlash of a Detroit Locker commonly causes synchro problems. My Detroit Locker did the same thing, it made my shifting more prone to grind a bit between gears.

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