Guys

I'm having a continuing and frustrating problem with my 914 rally car which is presently preventing me from entering any events.

The problem is this: when up shifting or down shifting to 4th, sometimes it goes into 4th so that when I drop the clutch it's in 4th gear. While other times, I drop the clutch and it's as if it's in neutral. There's seemingly no noticeable difference from the gear stick whether it's in gear or not. It's a complete unknown as to whether or not it's in ot not. The only way I know is when I drop the clutch and give it some loud pedal, sometimes it's in 4th gear and we're continuing with our forward momentum, while other times it's seemingly in neutral, the rev's go skywards and we start coasting.

Today, when it did this, i.e. I shifted into 4th and all I got was neutral (or no gear), I stopped the car and took a picture of the gear selector at the gearbox end to see if there's anything amiss. I also took some measurements of the distance that the base of the selector was from the surface of the gearbox.





I then continued my journey, got it into 4th gear properly, stopped the car and did the same. There is NO discernible difference at all to the position of the gearbox selector. The measurements are also exactly the same. So from the outside, the selector is in exactly the same position.

The ONLY difference is that when I'm in actually in 4th I can wiggle the gear stick a little to the right. But when it's doing that weird thing where it feels like it's in 4th but isn't there is no lateral movement in the gear stick to the right. It's as if it's jammed against something.

I thought this was something to do with the gearbox, so I had it looked at and refreshed. But it's still doing it much to my annoyance.

What could be causing this?

Additional info: I have a Rennshift shifter, and a complete Rennshift setup all the way from the gear shifter to the gearbox, and have had for some years. The gear stick is adjusted according to the manual (same way I've done it for years) and it selects all the other gears, every time, with no problem. I also have solid mounts up front on the engine and stiff rubber mounts at the gearbox end.

It seems to do this more often when I'm in race mode or vigorous driving mode. Driving like miss daisy it goes into 4th every time.

I don't know much about gearboxes at all, but to me it feels as if the shift fork is going under the shifter selector thing for 4th and 5th in the gearbox and get's wedged there. Hence not selecting 4th but feeling all the world like it's gone in there as it's moved (at the gear stick end) into that 4th gear position. I'm wondering if there's some kind of shim I've accidentally lost that is supposed to go on the shifter fork thing that goes into the gearbox that stops it travelling to far downwards and hence under the 4th/5th selector thingy.

I'm really starting to loose my marbles with this problem as it's costing precious racing time. Please help

Maybe look in the center tunnel to see if anything is getting in the way when in the 4th position. Cable, clutch tube...or maybe something in the transmission

That's a tough one, good luck

I had a good look in the tunnel and can see nothing that would interfere with the gear linkage when going into 4th. But thanks for the tip.

Have you repaired the clutch tube?
When you roll the shifter into 4th/5th plane its right above the clutch tube. I repaired mine and left it a bit too high. Pushed it down just a smidgen and I was good to go.
My .02c for the am.

Also, check the shift coupling in the tunnel forward the firewall. When the bushings fail this will happen.

If you are running aftermarket seat belts and use aftermarket seatbelt bolts with quick disconnect rings, sometimes the bolts are too long. If the bolts are too long they can interfere with the shift rod. A thought.

Thanks guys

I checked with a mirror and flash light that there's nothing interfering with the shift rod, from the shifter end all the way to the firewall bush, when it's engaging into the 4th position.

I can also confirm that the firewall bush is in perfect condition.

Are there any gearbox experts out there that can confirm if it's possible that the shifter fork can indeed slip under the 4th selector inside the box, if the selector fork moves too far downwards? What prevents the shifter fork from being able to do this? is there something obvious that prevents it?

Under, no.
It's on a shaft, with a pin.

I would suggest you pull the shifter console out of the tranny and get something onto that shifter fork to see if it's loose.

You seem to have checked everything you can externally, so a slightly invasive procedure may be called for.

Remove the shifter Rod and coupled.
Remove the shifter console which will take the ball on the outside and the fork on the inside out of the tranny.

Now you can see the shifter forks
Put it in neutral before you try and get the console out.
It's a simple procedure to allow you to make sure the forks are not broken and still attached.
Wiggle the rods also to make sure they are seared properly.

The more invasive procedure is to pull out the gear stack, which you may end up doing anyways.....Dr Evil has a set of directions in his signature here to help you do that one.

Rich

I know you said it is adjusted according the the rennshifter. I've heard great things about those but never had one. Almost sounds to me like you don't have enough throw going to 4th. So where it is set is right on the edge of engaging or not. A little more throw may be all you need. If you've already tried this ignore me. I had this happen with one of my 914's. I adjusted the linkage to give just a little more throw & all was good. Other than that I would do as Rich suggested & pull your shift rod coupling out to check on the forks.

I bought a $15 USB endoscope today. SO next time it does this I'm gonna stick a camera in there and see what I can see. I'll get to the bottom of this mystery yet

I have to echo JRust. The Rennshifter is a great piece of kit, but it must be set exactly or it will not work and give you headaches. You sound as if you are not getting enough forward throw. Interestingly, in your pic of the rear coupling your shifter is butted up to the fixture. This may be a limiting step that needs adjusted. If your coupler is not allowed to push the ball all the way back then 4th will be elusive. It is highly unlikely that your internal parts are the problem.

Are you sure that the coupler is set correctly on the custom shift shaft? One sure way to assure it is not the internals is to remove the shift rod and coupler and put it in gear by hand. I bet you can, and repeatedly. I wish I were there because writing about it takes a lot of words where me actually diagnosing and fixing it would take 15-30min.

This is what I was going to suggest. It should tell you if the problem is before or after the shift console. I'm betting it's before.