Had my first autocross in 3 years this weekend and everything went better than expected. Towards the end of the day (dual entered the car), 3rd gear started acting up on me. It was acting like it was physically locked out... It wouldn't go in without a fight even in the pits.

I simply ran the last two runs in 2nd and figured I was out of luck. Packed up and low and behold, 3rd was back. A bit notchy compared to the other gears, but didn't grind and really didn't make much of a fuss.

Anything I should consider other than a linkage issue?

Here is my current setup:

Rennshift
Bronze side shift console bushing
Swepco 201
...everything else normal.

I have one of Chris' fancy firewall bushings to go in, so I'll be taking everything out (linkage wise) to inspect. I half wonder if that bronze bushing worked it's way out...

Definitely always check and rule out external things like linkage, bushings, screws, mounts.

For this to be an internal problem you would need something to stop the slider from engaging. Since no grinding, the slider is not even getting to the teeth on your hub so either:
A) something is blocking it.
B) Ya got some hillbilly teeth in there

In A, a broken block inside the synchro band can do this. It forces the band outward and keeps it from collapsing which prevents the slider from going into place and keeps it from hitting the teeth of the hub, often. Sometimes an up or down shift seems to resolve this issue momentarily.

In B, well you would have had some grinding to get to this stage.

If external stuff checks out, pull the stack. Id be happy to help, it would be an easy fix of just the stack.

Poached this pic from Pelican. It shows better what I was trying to explain.

This is the newer style, 73 and up, of internal parts for the gear synchro assembly. The lower block can break, usually along the yellow line, and it will jam up one of the internal bands which then keeps the synchro band from compressing (which has to happen to allow the slider to engage the synchro hub and thus select the gear). The block can break on either side, and one side is up shift, the other is down shift (that's why there is two internal bands). Ironically, sometimes a break of the block causes the gear to pop out as the band cannot push against the synchro band and lock it in place once the gear is selected.

A problem with only one gear is more likely to be inside the box than a problem with all gears.

I had 2nd gear become unselectable for a while (it came back after a while) when some very weird damage happened to some of the hub parts in the box. I have pics posted around here somewhere.

By all means try all of the adjustments and such that you can; they are a ton cheaper and easier then disassembling the gear box. Just keep in mind that you might wind up having to dig in there...

--DD

Doc, I was hoping you would reply. I’ve had your DVD forever. Time to start watching...

Dave, I’m hoping it’s external, but this box has been “difficult” for years. I’ve had the stack out a few times to inspect it and it looked great. I may just build up a box with Dr. Evils video leading me - I have a ton of spare parts.

With the parts I posted, it would look externally ok for a while

If nothing shows up I’ll consider pulling the stack again, but I’d really like to do a short box (especially 3rd) for autocross, so it might be just as fast to build one from my spares.

Totally. If you have a spare(s), then you have all you need.

Interesting. I have an intermittent lock out on my 4th gear. Most of the time, flawless shifting. Out of the blue fourth gear is impossible to engage. Then, after stopping the vehicle, shutting down the engine, and having exactly one beer served at precisely 43.7 degrees, the gear returns to the party. but...Warm beer/ no gear.

In all seriousness the gearbox seems to be the issue. My linkage is solid in all respects and when things are going well it is flawless to the extent that a 300 dollar side shift box bought sight unseen can go.

Q: Does the good doctor have a service whereby I could pluck the gear stack out of the box and send it off for a real inspection and a full refurb? Thanks to my pal Keith, I now have located an enclosed garage in Laguna (a rarity indeed) and can stash the car and case while it is in the care of the good Dr.

My goal would be to have this work done prior to the Rt66.

Please PM if there is a path to transmission remission.

Spent yesterday afternoon putting in a Tangerine Racing spherical firewall bushing. This afforded me an opportunity to take the entire shift linkage out of the car. Everything looks good there. While I need to do more work to set the bushing up correctly and adjust the shifter, the strangeness in 3rd seems to still be there. Sigh...

Yup. Ill PM ya.