901/911 Transmission issue

[seafeye]

1971 911E. 901/911 Transmission.

Been trying to sort out why the car wants to jump out of 4th gear each time I Step on the gas...
Took the motor trans out today. Disassembled the gear box.
I seem to have the same friction popping it into 4th and 5th.

Was rebuilt less than 500 miles ago. With new synchros.
I’m pretty gentle on the car shifting. New mounts etc...

Any ideas what the culprit is?

[seafeye]

In between 4th and 5th



In 4th






5th

[Trackrash]

The "teeth" on the inside of the slider are tapered and will "hold" onto the synchro ring, since it is crowned in the middle.

Compare pulling the slider out of fourth and out fifth after engaging them.

Was the slider replaced during the rebuild?

Take a close look at the dog teeth. Are the edges rounded off?

[Trackrash]

[seafeye]

Here are better pictures of the dog teeth. I can’t remember if I did the sliders or not. I’ll look up the bill. It’s pretty difficult to say if 4th is easier to disengage than 5th. I can get a better grip on 4th making it easier.
Here is 4th...


And 5th

[seafeye]

The top bearing race was fairly easy to remove. So I pulled the gears off. Here is 4th

And the slider ring...

[seafeye]

I pulled 4th and 5th off the spindle. So I can lay them flat on the bench and click in the slider equally on both.
It honestly seems equal. I think I’m barking up the wrong tree with this being the reason why it was popping out of 4th.

Could be my actual shifter. But that was rebuilt. New bushings etc... new shift coupling...

I dunno. Nothing looks broke with 4th.

[Trackrash]

Those parts look good from the pics. Perhaps others will have a better idea.

Did this just start happening? Or was it that way right after the rebuild?

Maybe post over in the 911 Technical forum.

[seafeye]

Never really drove the car prior to rebuilding it. So unfortunately no previous experience. But from day 1 of getting it on the road again it wasn’t staying in 4th.

[Jon B]

Seafeye, these are all pictures of your 2nd and 3rd gears, NOT your 4th and 5th gears...

Originally Posted by seafeye

In between 4th and 5th



In 4th






5th

[seafeye]

Transmission for beginners... I’ll look at the other shaft. Thx.

[356RS]

You gotta Love Jon. This is great.

[MBEngineering]

HI seafeye

so you have a 1971 2.2Lt , 911 Mag case gearbox,

Pondering 10 peneth of thaughts on your gearbox prob'

when you built up all the shafts into the center bearing plate, what did you do about setting the selector forks up in the worn case holes, where the selector shafts fit,

did you torque up the nut and pinion bolt and how much movement in the 2 flanged bearings was there, that might make the shafts move back and forwards,

you did build the gearbox dry and removed all parts off the shafts before assemble, put the correct washers back in the correct places and the correct way round.

just checking things before saying the 4th dog teeth may be worn out and the slider could have been turned on re-assembly, if not re-placed ?

[faapgar]

Hi,slider for 2-3 has wear where it contacts the synchro.Do you have standard shift coupler or aftermarket.IF you want to run it up to me here I can scope out what you need.i am in Pinehurst.I have new parts to compare for wear.Price is a good local craft beer.Ciao

[Tom Elder]

Hi, seafeye
I had this issue with a vw type 1 transaxle after changing the ring and pinion. Worked fine for a few hundred kilometers then started jumping out of 4th. Shift fork had slipped on the shaft. Set the fork up again, little over torque and locktite on the bolt. Never had the issue again. Hope your issue is as simple.
Cheers, Tom

[seafeye]

Thanks Tom

I got a new slider for 4th 5th. I’ll try get this together in the next week.

[seafeye]

Put a new slider in for 4th and 5th. New synchro for good measure. Got the transmission back together with the help of a friend. But putting it on the engine I broke the clutch fork spring. Doh!

So I won’t be putting the engine in till I get a new spring.

[seafeye]

Well all back in.... also replaced the banana arms, had a spare set so I put in solid bushings.
Test drive in 10 min....

[Walt Fricke]

Solid bushings? Where - the trailing arm inner mounts? Were these the Weltmeister urethane bushings? Those are a bad idea, as they don't have the compliance needed. The stock rubber provides that, since the arm twists several different ways as the wheel moves up and down.

What you want are spherical bearings there, which Elephant and others. sell. Or are those what you called solid?

[seafeye]

Yes. They are the stomski spherical bearings. Car feels great. I’m glad I did the visibly unnoticeable upgrade. Also has the stomski solid transmission mounts.