First gear selection problem - help!
 

I am about to embark on a project to change 2nd, 3rd and 4th ratios in my 4 speed tranny, BUT, I have another problem I’d like to solve while I’m in there.

First gear is really hard to engage sometimes.
It’s a regular PITA at the lights or stop signs as I frantically try to grab first … clutch in / try first gear, no go / clutch out / clutch in again / look at pi$$ed off driver in mirror / try again / try second, no problem / try first again, no go / back to second and off we go, v slowly! :mad:
It might work fine for days and then catch me out right when I am next to some redneck in his monster truck or a little ol’ lady in her Toyota Yaris. As they head off down the road, I’m left behind playing with my knob :o

I initially thought it was just a synchro ring problem so last time I had the tranny out, I replaced the synchro ring (41) only. It looked a little worn but serviceable, so I changed it anyway. I couldn’t see any other obvious wear problems on dog teeth on 1st gear (48) or the brake band and blocks (38, 47, 47a) so I reused them all. End result was no change.

I’ll try to explain how the gear-change feels so that hopefully someone here will recognise the symptoms and point me to the problem.
The problem occurs about 30% of times when trying to select first, usually with car stopped.
Most times, it slides straight into gear, but sometimes the gear lever just seems to come up against something solid. If I push really hard it sometimes goes in, but I can feel the shift mechanism flexing under the load. Its almost like the slider (45) is blocked from moving and I can visualise the fork and selector shaft bending – not nice! :eek:
With the clutch in and pushing the lever into 1st, if I hold pressure against the stick and ever so gently let out the clutch, just as the clutch starts to bite and things start turning in the tranny, the gear will engage.
Changing down from second into first on the move usually works OK. However, for a while I’ve been double de-clutching for each change into first and it has no beneficial effect. Sometimes works, sometimes not.

So, over to you – what’s the problem? :confused:
Which bits do I need to order?

By the way, which parts should I replace when I fit my new 2nd, 3rd and 4th gears?
I am installing 2nd 17/26 (1.53:1), 3rd 26/27 (1.04:1), 4th 30/23 (0.77:1).


http://forums.pelicanparts.com/uploa...1247029296.jpg

NOTHING technical to share with you Bill, but wanted to say that mine with 45k does the same thing. Sometimes for reverse as well. Box was apart when PO had 3rd rebuilt (grinding every time) and nothing was done to rest of box as all was said to 'look fine'.

What I've found 'gets me around it', is grabbing 2nd, letting the clutch out a hair for a spit second, then grabbing 1st. It's almost as if it's just not lining up and the subtle change in the car's position (roll forward) allows it to engage.

Like you said, totally intermittent.

I also get crazy grind in 1st / R on an equally intermittent basis, out of nowhere, for no reason. As if the innards are just spinning too fast to grab (major technical description there huh)? Mostly after prolonged idle or rev-up. I've learned to 'ask' for the engagement first by 'testing the water' before going for the full grab. No idea what gives, but box was said to be 'fine'. Dunno.

Hope that least provides you a datapoint. Good luck.

930
 

Sounds to me like a combination of the slider and possibly the inside diameter of the dog teeth worn letting the outside dia. of the new syncro to be too large and kind of "block" the slider from moving over and compressing the syncro. also when the sliders wear or get abused they after a few shifts look like they are OK, but its job is like a brake drum and the syncro is like a brake shoe, so the dimensions are critical to shift well, Too many years ago when I started doing these gearboxes I had one that had the typical issues freshened it with what looked worn and after a couple more times on the bench changed the dogs,sliders, and it worked perfect. Good luck and let us know how it goes.

Mike Bruns JBRacing.com

Paul,
At least I don't have any gear cruching problems.
I sometimes pull the stick back against 2nd but not fully engage it. This seems to help sometimes.

Mike,
I don't believe it is related to the synchro ring and dog teeth.
I fitted a new synchro ring and it didn't make any difference at all. Even if the inside of the dog teeth were worn, I would have expected a new synchro ring to have made some difference.
I am leaning towards the brake band and blocks, but I'm not really sure how they work. I guess there's not much else in there to go wrong, is there? :confused:

Mine does the same thing. I have tried putting it is 3rd, 2nd, and then finally 1st which seemed to help but was terribly time consuming. Now I have figured out that all I have to do is release the clutch while in neutral and then press it again and all is silky smooth. I can do this quickly and it works every time.

930
 

Bill, does your box have the late style asymetrical dogs/slider for 1st or the early style like the rest of the gears ? I still think you have a slider issue from what you describe.
Mike Bruns

OK, mine does it too....so I guess I can join the club. Maybe 10% of the time, it takes a real firm push to get into first (if at all), sometimes going into second then into first works and sometimes not. I usually try to grab first gear while still rollling to a stop when possible. Most of the time it slides in smoothly.

When this happens, I usually just break into one of my favorite songs and "get over it". Embarassing to have someone behind you, whilst you wrestle with the @#$%$^%# shift lever. People give you dirty looks, like "you stinkin' rich a-hole, if you can't drive it then you don't deserve to own it".

If anyone finds out how to resolve this issue...It will be Gold..and please post for all...

I have the same issue with mine...

Same with mine!

Well, their pretty much all like that, welcome to the world of the 930 4spd. You can always cure it with a G50 & your wallet!
Or, you can simply console yourself with the knowledge that...at least it's not a straight cut gear, non-syncro British tranny!
Mark

same here, double clutching works best on mine, or into 2nd first

Heh - mebbe "that's" why I've become so adept @ me process - you just described my TR3 8-)...

Add me to the dog pile.

I just go from neutral to 2nd to 1st. Doesn't always work, but does most of the time. The other option is to place it in 1st as you creep to a stop, but then you have to hold the clutch in.

my first gear is probably 80% not able to engage from a dead stop. if i roll the car slightly the gear will engage. i recently replaced the rear shift coupler bushingd as they were so worn that in the second day of a de at mid ohio i lost reverse.
the new bushings have fixed reverse gear and it goes in smoothly now. i also replaced a leaking cover on the tranny case that holds the shift fork guide. it was bolted tightly to the cover which sometimes is an issue if the nuts loosening the fork guide is loose. the bushings allowed very little slop and it surprised me how little slop completely prevented engaging reverse.
try this fix to see if it helps.
but it appears this is a design problem with so many having issues with first gear. i cannot say it fixed mine either as it still balks sometimes into first. i cannot say how old the synchros in my 79 4 speed are though.
good thread.....lets get more input.

Apparently all the 930 gearboxes do that. It would be nice to try a new gearbox and see if it does it.

where's the guy that just bought the grey 930 with 38 miles... ?

Probably won't shift at all, the aged gear oil now being the consistency of bees wax. :)

My 915 (NA car, but the Turbo forum has good info so I browse from time to time) does this on occasion, especially if I hold the clutch in while stoping and don't shift to 1st while still moving. Sounds to me like is a design "feature" of the 901/915/930 design thats more prominent on the 930 because you guys use 1st gear more.

I've found that for me, either releasing the clutch in neutral then waiting a split second before trying again works 90% of the time. That failing, I do the same except go to 2nd then 1st. My guess is the dog teeth are lining up so that instead of meshing they are hitting each other when the gears are still. If, however the layshaft is spinning (having been spun by letting off the clutch) then they synchro can stop them and hopefully line the grooves up properly.

Personally, unless I know its a long light I just drop her into 1st as I stop and hold the clutch. Here in LA if you spend more than .001 seconds sitting at a green someone will run you over :). If its a long light, I'll usually watch for the turn light and make sure to get in gear early.

I'm just soooo glad that that so many others have the same problem.
Gives me that warm fuzzy kumbaya feeling. :D

We need to keep at this - there has to be at least one guy out there who successfully identified and fixed this problem!

Service Bulletin
 

I have also found the following service bulletin which may be relevant. My car is an '86 model. Porsche introduced this fix in '87.
Anyone had any experience of this ...

http://forums.pelicanparts.com/uploa...1247099143.jpg

Let me add my data point...

'79 here with a recently refreshed box. By refreshed, I mean new dog teeth, sliders and synchro rings everywhere...except the 4th gear dogs which showed little wear. Also have a new clutch, the Wevo shifter and recent shifter bushings/coupler, etc. So its all pretty fresh.

I usually have no problems getting into first while stopped. I will say that on occasion it refuses to go in, and I do a double clutch or grab 2nd and then 1st. I do try to always touch 2nd before 1st. I read somewhere (on this forum most likely) that this is the 'proper' technique, and that putting the clutch in while in third gear, coming to a stop and then selecting 1st without touching 2nd is asking the synchro to do something its not designed for.

Just to clarify my own understanding...I always thought that the "synchro rings" and "brake bands" are the same thing. Am I off the mark on this...never been inside a gearbox by myself and terrified of their mysterious inner workings.

I'll join this club. I thought I had a problem with the linkages. I've tried double clutching but that doesn't always work either.

billjam

Where did you get the Service Bulletin? Is there a on-line source for them. Or is part of the workshop manual?

Also, does anybody know where to get the Porsche Parts Technical Reference Guide (I think it is)? I have it packed away somewhere, and it's got some good info.

Wow, that's good $hit! I forgot to mention that beyond the periodic first gear difficulty, I also find getting into 2nd requires more force than I think it should. Have never "Not" been able to get it in, but depending on the rpms and how warm the tranny is, sometimes I have to pull it in, vs. slipping it in. If I ever decide to crack open the transmission, that's the first place I'll look.

I picked this up when I bought a CD copy of the 930 factory manuals and PET a couple of years back.
The service bulletins are in a 562 page PDF file which has a file size of 42MB (= large).
Also on the disk with the 930 manuals were a few other odd files including factory and Bentley Carrera manuals, 68-88 tune-up specs and 84-87 Technical Specs.

I don't recall how I came across the seller of this, but I guess a search for Porsche manuals or PET might find him somewhere (if he's not in gaol :rolleyes: ).

Update - problem fixed
 

Four weeks on I have rectified this problem.
While I had my box apart for new close ratio gears (2nd:), 3rd:eek: and 4th:cool:), I revisited first gear looking for anything out of spec.
It really didn't take much time to identify that the dog teeth were a little worn. Instead of nice sharp edges on the teeth, they were quite rounded. I really should have picked this up last time is was in there.

The good news is that the dog teeth ring is available as a separate part. I've bought them before from Pelican but this time I got it from Albins (here in Aus) for $A153 (about $US120), who also supplied my C/R gear set.

It is a bit of a battle to remove the old ring without the special tool, however I managed it by cutting through most of the ring with a Dremel, then splitting it with a chisel.
Pressing the new one on to the gear takes a fair bit of effort, but again I managed it without any special tools.

Gearchange into first is now much easier. Actually it's not so much that it is easier, it just goes in more often than it did before! The change into first is still quite firm, but now it goes in every time. :)

This picture shows what to look for. The old dog teeth ring is obviously the one with rounded off teeth.

http://forums.pelicanparts.com/uploa...1249220573.jpg

http://forums.pelicanparts.com/uploa...1249220605.jpg

http://forums.pelicanparts.com/uploa...1249220644.jpg

Yepper....them look like some tired dogs to me. Thanks for sharing your resolution to the problem.

Billjam and Forum,

here some pictures of my dog teeth of the 5th gear and slider.

I am having difficulties to rate them. I have no datum.

http://forums.pelicanparts.com/uploa...1363417982.jpg

http://forums.pelicanparts.com/uploa...1363418065.jpg

How can I rate them. Are they worn out?

BR
Bob

Bob,
I am no gearbox guru, but I can offer a comparison pic between old and new dog teeth rings, albeit for first gear, not 5th.
The 1st gear teeth are not symmetrical - one face is wider than the other but all other gears have symmetrical teeth. However the critical issue is the rounding of the top edge of the teeth. You can see the difference between old and new in the pic below.

Looking at your pictures, the dog teeth look a bit tired but the teeth on the slider look passable to me.
I guess it all depends upon how much of the "while you're in there" budget has been used up. Personally, I'd just replace the dog teeth ring and take a risk on the slider, especially if this for your 72 T. This part is about $800 from our host! :eek: Most other models seem to be more like $200.

http://forums.pelicanparts.com/uploa...1363435837.jpg

Bill thank you for your pictures,

Your dog teeth new looks way different to me than mine.

My ones do not have this nice triangel shape. Do you have a picture of a new dog teeth in the same orientation?

BR
Bob

The best I can do is this shot of a new 930 4th gear.

http://forums.pelicanparts.com/uploa...1363483312.jpg

Bill you were defining wear on the rounding of the edges.

You said.

However the critical issue is the rounding of the top edge of the teeth

Do you mean the section which I marked in red?

I don´t see much different on your new 4th do teehs to the used one.

See my pictures. Is the right side used?

http://forums.pelicanparts.com/uploa...1363508511.jpg


http://forums.pelicanparts.com/uploa...1363508561.jpg


BR
Bob

Bob, the face you have marked in red isn't the one which is subject to wear.
When the dog teeth are worn, it is the pink edges that get rounded off.

http://forums.pelicanparts.com/uploa...1363522676.jpg

http://forums.pelicanparts.com/uploa...1363522366.jpg