Big trouble? Can't engage 3rd/4th. UPDATE POST 17

[SeriesShorty]

History:

I took my truck down about 16 months ago to rewire and convert to 12v. Ended up moving to a new house and had the Series towed on a front wheel dolly. Dropped the front driveshaft and put everything in neutral.

Just got it running good enough for its first drive yesterday. Cannot shift into 3rd/4th gear. I'm assuming something went awry during towing but that may help pinpoint what happened.

Took the shifter apart and took the top cover on the case apart to do a quick inspection and to tinker around. There isn't anything obvious that stands out to why the shifter isn't moving at all.

Any ideas on what happened or suggestions on how to go about troubleshooting this?

Thanks all!
J

[artpeck]

Does it shift while the engine is off? Or with the transfer case in neutral?

[Terrys]

Im assuming from what you said that you have the tunnel off. Can you see that the ball on the end of the shift lever is fully into the socket of the 3/4 selector shaft?(the one on the left side) If so, can you then see if the shaft "wants" to move fore or aft, or does the whole shaft seem frozen.
When you say everything was in neutral, I'm assuming you mean the TC and trans., The "rule' is to put TC in neutral, and trans in 4th, but so long as at least the TC was in neutral, and depending on how long the tow was, you may simply have a gear that doesn't want to slide on a rusty mainshaft.

[SeriesShorty]

Doesn't shift into 3rd/4th at all, engine running or not, TC in neutral or not.

Reverse, 1st/2nd are smooth as silk. The ball of the shifter fits cleanly into the cup for the 3/4, but seems frozen in place.

Took the shifter off and tried to pry the shaft into place thinking something was just rusty or gummed up. But no luck there either. The gearbox has 15k on it, and I had just changed the fluids before I took the truck down last year. Its clean as a whistle inside.

I'm gonna start labeling up some ziplocs just in case I need to start taking this thing out.

[tuko]

Dropped the front driveshaft and put everything in neutral.

Removing the front drive shaft does nothing really as it simply floats till 4 wheel drive is engaged.

I think that it would be wise tomorrow to remove the transmission top cover to see 1) if the selector shaft is frozen in place, 2) the selector fork is engaged in it's corresponding groove.

Possibly a silly question but did you try to move the Landy under it own power? I'm just trying to determine if the transmission or transfer case has any form of binding in it.


Todd.

[Apis Mellifera]

I amazed how often my answers to tech questions involve the detent springs and balls.

I'd check that - it's easy, especially since you have the gearbox tunnel off. The 3/4 detent mechanism is a pretty poor design. It's a steel ball in a close tolerance aluminum cylinder. It's easy for the cylinder to get out-of-round because half the cylinder is in the gearbox case and half is in the top cover. It's more likely that the ball is tight in the hole and once shifted into 3 or 4, the ball sticks in the "out" position and the spring isn't able to return it into the detent on the shaft. I believe this is perhaps a more likely cause of jumping out of 3rd than a missing syncro spring. Any way, it's possible that with the already tight tolerance and dissimilar metals combined with a prolonged lack of use that the ball is stuck in the "in" position, preventing 3/4 shifting.

I don't think that's likely, btw, but it's possible. The next likely cause is the syncro. You'll have to open it up to inspect that.

[cousindave]

I had a similar problem with my series III. The 3/4 syncro spring had turned 90° in the syncro assembly. Simple fix with a screwdriver. I do agree that you should check and clean the detent springs first before opening the top cover.

[SeriesShorty]

Tooks the "balls" and springs out when I took the top cover off so they couldn't have caused any binding. With everything out of the way the shaft still doesn't move.

Any other thoughts?

[I Leak Oil]

As was mentioned, the 3-4 synchro....with the cover removed and the shift fork out you should be able to move it. If you can't you've probably found the problem.

[SeriesShorty]

That is what I was afraid of, but wanted to rule out anything else I could be overlooking.

Anything else I should tackle as good measure while I've got the gearbox out? I've got new mounts so I'll throw those on while I'm at it.

[Terrys]

Don't give up hope yet. Apis was alluding to the detents balls, but, while not trying to put words in his mouth, may have also been alluding to the interlock plungers. I call them shuttle plungers, but that's me. They prevent either the 3/4 selector shaft, or the reverse selector shaft from moving if the 1/2 selector shaft is out off 'neutral' position, and so forth. There is a pin, which passes thru the 1/2 selector shaft which is steel, and may have rusted. These two shuttle interlocks and the pin must be free to float back and forth as necessary or one of either the reverse, or 3/4 selector will be 'locked-out'. Only way to check is to remove the top cover. Be sure to get the 1/2 detent ball out before raising the cover, or have a long flexible magnet at the ready, to fish it out of the sump.

[Apis Mellifera]

This basically a case of trying to shift into 3 or 4 and jiggling things to see whats not jiggling. I don't know how to put it any other way, but the bit that isn't jiggling is the stuck bit.

Since you have the top cover off already, take the above mentioned magnet-on-shaft and probe the depths to see if you can fish out a broken syncro spring. They are thin spring steel and there should be three. A missing spring won't really lock out shift, but one that's misaligned and jammed in the syncro could. Terry is spot on with the interlock mechanism and the 1/2 detent ball, but with the top off, you've already ruled those out.

Put the shifter back on with the top off and see what moves. It basically goes: you move the shift lever, that moves the shaft, that moves the attached shift fork, that moves the syncro. If you find that you have some wiggling down to the shift fork on the syncro, while trying to shift, give the syncro a light wrap. You may have to wiggle the trans brake a little too.

[cousindave]

Shorty, you don't need to take the tranny out yet. Just the top cover and the selector forks. A good light to see inside. These gearboxes are pretty simple and forgiving of super precise measurements. Like apis said juggle it, wiggle it and wrap on it (I think there's a song there!)until you see what is keeping the 3/4 from shifting. Good luck!

[Terrys]

Like apis said juggle it, wiggle it and wrap on it

a foot of broom stick and a bfh.

[scatterling]

Jen, with the top cover off and the gear selectors removed, look in and forward of the top cover. You should be able to see the 3/4 synchro. You should be able to (with some effort) move the synchro by hand into 3rd or forth. If it won't move check by sight or by feel if the synchro springs are in place around the synchro. There are 3, they are somewhat flatish and about 1 1/2" long. One or more might be bent, jammed, broken or missing. It is possible to replace the springs with the gearbox in the truck. It does involve some blood and bruising but it is doable.

http://www.roversnorth.com/forums/showthread.php?t=6969&highlight=synchro+spring