Hi.

I am planning to address the grinding I get when going into 1st gear at anything faster than a full stop. The Pelican article on the replacing first gear seems pretty good, and I plan to search these pages for nuggets of wisdom before starting.

This thing has been grinding as long as I have had it and certainly long before that ... so I figure it is in pretty bad shape.

Pelican suggests the following parts: slider, shift fork, synchro ring and brake band, dog teeth, and maybe first gear if it is worn. I plan to open it up before getting parts - and I assume they are all available without much trouble.

I'd appreciate your thoughts on tackling this project as well as any advice.

Thanks. Christian

You do know there isn’t any syncro from 2nd to first, you basically have to let the gears mesh up to shift.

Dr Evil may have some of the parts both new or used...
Ill look for links of the you tubes I recorded when I updated mine

-Robert

My experience, after rebuilding a couple dozen transmissions over the past couple years is it’s rarely just first gear. That gear might be giving you most of the issues but unless it’s a really low mileage trans, there’s probably more to do. You will know once you open it up.
Before you get too far into it, you can open up the side cover and inspect the ring and pinion. A damaged r&p pretty much disqualifies the trans from getting rebuilt.

That is incorrect, there is a synchro on 1st gear. In stock form, it's a different one from the others, but any of the other synchros can be used as long as you use the other parts (e.g., the stop blocks and maybe other stuff) that go with them.

A number of old cars do not have synchros on first gear. AFAIK, all Porsches have always had 1st gear synchros. (Possibly some very early 356es did not, but the later ones did!)

--DD

1st can be done in the car, easiest if you have a lift but do-able on stands.
You'll definitely need a slider, the 1st/reverse syncro (which is spendy) & dog teeth.
Doubtful you'll need a fork or brake bands/block.
As others mention the 1st revers syncro is usually perished if it hant been touched in 50 yrs but normally 2nd is also pretty hammered which means pulling the stack.

No one has said it yet...

The EVIL Doctor is the BOMB regarding these transmissions!

I would get/search EVERYTHING he has posted.

To me (I'm experienced) his info is the GOLD standard even beyond Porsche themselves.

Hit up the Dr early instead of late. He is one of those special guys you gained access to by joining the forum.

Has anyone on this board ever down shifted from 3000 rpm in second gear to first, and had their tranny survive. No need to try.

Please observe parts 41, 8 and 9. Syncro only on one side, up shift only.

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Just saying.

You may find this helpful: http://www.914world.com/bbs2/index.php?sho...=376106&hl=


I have done 3 of these

One with 20K miles
1st gear - replaced dog teeth and Sync Ring
2nd gear - replaced dog teeth, Sync Ring AND swapped 4/5 selector with the 2/3
One with 90K miles
1st gear - replaced dog teeth and Sync Ring
1st gear - replaced the 1/R Selector -
2nd gear - replaced dog teeth, Sync Ring
2nd/3rd - replaced Selector - it was too far gone to move to 4/5
One with ? miles that was from a 1970 burn-down in 1984
just replaced the sync rings in 1st and 2nd and a dog teeth in 2nd

Dr. Evil's videos are a MUST - unless you were factory trained or similar 901/915 tranny work, start with the videos.....all of the tricks are in them

ALSO - VERY IMPORTANT

The linkage - setup, bushings, wear need to be addressed - short money and will tear the transmission apart if not addressed - every-time you go in, replace all of the bushings.

I have never replaced a gear. All of them were perfect.

The beauty of the design is that the gears are always protected by the dog teeth - it takes a great deal of abuse to grind the dogs to the point that the gears are not turning in sync. What you are hearing is the dog teeth protecting the gears. This happens because the sync rings are warn-out.

Happiness is the first time downshifting to first while rolling and there is no noise......Ahhhhhhhhh

The difference in gear-spin is pretty severe at that end of the gear train, when everything is new, and you do it slowly (3 Mississippi's) it should work, however, the sync rings will suffer.

sure have had missed shifts on the track

usually zings a valve on a six

but tranny survives

our race box (always new sliders and in great condition)
can easily down shift in anger and does so frequently...
increased wear that is addressed when needed to maintain performance


F, J, O, S, V (904 mainshaft)
tilton twin disc 5.5 inch clutch
flywheel in the range of 4-5lbs
TB LSD
billet intermediate, side plates and cooling
no reverse gear (try to fit " F" into first and youll see why)

Actually, those are the brake bands and stops/anchor block/thrust block. The "syncros" (synchronizer rings) are actually #10.

And yes, only one brake band on first gear (although, IIRC you can use parts from gears 2-5 to run two brake bands on first gear if you want to for some reason).

43 is $$$$$

Dr. Evil sold me one that was really good - I bought a core to raid for parts and it was the cleanest transmission of all of the ones I have!!!! Sometimes you get lucky.

easily done with the transmission in the car, just remove the muffler and the rear cover. We have sold many many first gear repair kits over the years and the kit comes with instructions, easily done in less than two hours

Yes, lots of $$$ . Fortunately, we have a NOS one in our hoard

I've been away from this forum for some time (life got in the way) and it is good to be back. Just this string reminds me of what an amazing community we have. So many thanks for all the feedback.

I am going to try to it with the trans in the car. I do have access to a lift, which will help.

But first will study up, especially on Dr. Evil posts.

My new week is bit busy but I should be able to do the teardown before long, after which I will report back on what I find!

Please keep us informed. The option of in car service has always intrigued me.

I have read in some other post about getting 1st gear syncro to work well, particularly when at full stop and trying to get into first, that there is a syncro that works better.
First gear syncro use part number 911 302 301 08

I have not used this before. When I rebuilt my transmission I put in new syncros on first and it works great if you are moving even the slightest. If you are at a full stop and the transmission is hot it can be difficult to get into first.

Others have thoughts on this?

john

A little sneak peak of what is involved: youtube links to my repair:
https://youtu.be/sZVd2ldRjmk
https://youtu.be/k5FpdBIMmJY
https://youtu.be/zULWZD_DBvI

These are great. Thanks!

LOL! Just because the parts are there doesn't mean they're in good shape.

And I'd be more worried about the engine and clutch than the trans at that point.

--DD

I finally found some time to tear into the transmission. The disassembly was pretty easy.

Dr. Evil's videos were worth every penny, even though I am not doing a full rebuild. It really helped me understand what goes on in that box when I shift gears and was a confidence booster for taking it apart.

There was not much metal on the plug magnets. Some, but I was expecting a golfball of metal fuzz. It was tricky to not have the middle section of the transmission come off with the end. That took some careful tapping.

The diagnosis and fix are clear - That dog don't bite, that's for sure (see pix). The slider teeth look like they have been smeared around. I'm certain I need new dog teeth, slider and synchro.

Now to get parts ...

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If first gear is gone, second is usually close behind.

I do have the tools needed for a small rental fee. Mark

Nice pics, thanks for posting

Sucker is toast

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If you haven't spend some time on the bird site and read about dog teeth from oem supplier that aren't ground quite right. The rausch and spiegel brand are correctly machined and fit to factory specs easily.

2nd gear takes a great deal of abuse - NOT the gear but the slider and DogTeeth

A good trick to save $$$ is to exchange the 2nd/3rd Slider with the 4th/5th slider.

The 4th/5th parts are not treated to as much abuse and are in good shape in near all cases,

Looking at your 1st Slider and DogTeeth pretty sure there are dogs barking from 1st to Second.

GOOD LUCK!

Thanks to all for the confirmation and advice.

I am going to be traveling in the next month so pulling the transmission for a complete rebuild is not going to happen this year. I'll stick with the "in the car" 1st gear fixes and make it in time for driving season to start. But I definitely get the point and it's on my project list.

I'll check out the bird on the dog tooth gear issues. I'd prefer to get this right the first time.

Sent you a pm

Today I separated the dog teeth and pressed in the new ones. It went really well.

Then I put some bright lights on the transmission to get the old gasket scraped off and saw something I wish I could unsee. The race of the bearing that sits under 1st gear is cracked in four places.

Maybe a full rebuild is going to happen sooner than I had hoped. Like maybe now.

Ugh ...

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You might have gotten lucky!

Finding crap like that NOW, before it has trashed any shafts or the case means you could have a good core that just requires normal rebuild parts.

I think you missed a bullet!

Zzz you’re half way there and you have the videos. Can borrow the tools. Keep going

I am going to go for it. Will report back!