901 problem with 1st gear

flash951 · 11-26-2010, 03:18 AM

Engaging 1st gear when still moving is not possible, only when completely stopped.
When stopped, there is no problem engaging 1st or reverse.
1st and reverse requires to press clutch pedal almost "all way down" Ive noticed.

All other gears are OK when moving, 2nd and 3nd needs a little "pause/stop" in center (0,2 sec), when shifting, I cant shift as fast as possible without "grind/noise".

Ive new clutch cable, new shift coupler, new bushings, and the rennshift shifter.

djpateman · 11-26-2010, 05:45 AM

The synchro dog teeth and the slider that engages them are probably completely worn out. This is quite common. Even the synchro brake band should be replaced. Basically it is about time for a transmission rebuild.

mcaterino · 11-26-2010, 05:49 AM

I'm in the middle of rebuilding my 1970 911 transmission. You can check out my current thread for an illustrated catalog of many of the things that can go wrong inside:

1970 (911/01) transmission refurb issues

The internal work is fun, and not all that difficult. But get your wallet ready if you decide to open it up.

Mike

klph · 11-26-2010, 06:06 AM

Hi

First post from me (73 911 Targa 2.7).Been lurking for a while, as I'm still pretty new to the 911 Universe.
But this sounds like something I experienced as well.
In my case, I couldn't engage the second gear while moving. After a quick glance at the Porsche site because you have a different car, (bear with my english please, I'm from Germany and don't have all the tech terms) I think you might have to adjust the rod that goes back to the transmission at the transmission coupling. You should have a cover just in front of the rear seats on the middle tunnel. Lift that and you can unclamp the rod from the coupling. Readjust as needed (in very small steps), and voilà.
Before you unclamp though be sure to mark the current position, so you can always go back.
There's a Porsche way to do this in the manual, which I don't currently have available, I just did it by feel, until all gears switched smoothly. The Porsche mech I told about this just laughed, and told me that my way worked as well.
Of course, if you did the work on the shifter yourself, you already know this, so then disregard.

Hope this helps

yelcab1 · 11-26-2010, 06:22 AM

By all means, try the adjustment first. But, it does sound like the 1/2 gears synchros and slider are beyond their useful life.

Bob Kontak · Bob Kontak's Garage

Here is a tech article on replacing the 1st gear parts on the 901.

Pelican Technical Article: Replacing 1st Gear on the 901 Transmission

flash951 · 11-26-2010, 06:37 AM

Thank you. I advert for a good 901 transmission on Internet then, to rebuild is maybe more expensive.

(Of course I have adjustet the shiftcoupler already.)

Flieger · Flieger's Garage

I would try another clutch adjustment first before a rebuild. It sounds like the clutch is not fully disengaging. Reverse is non-synchronized so it is the test for a sticky clutch. If you cannot get reverse without grinding after having the clutch pedal to the floor for a good few seconds, then the clutch likely is still dragging.

By the way, 901/911 transaxles are designed to only engage first while moving as a downshift from second. If you come down through the gears and engage first from second while at walking speed, do can you get it? The first gear synchro is asymmetrical so that there is much less synchronizing force when engaging first from neutral (upshift) so this should only be done while stopped.

Rusty 356 · 11-26-2010, 10:18 AM

Remi, as suggested do the adjustments first, then try, if still the same, when in second coming back to first, double clutch with a little rev boost and drop into first. Should drop right in, then when you finally want to rebuild the trans you can put in the new syncos and sliders.
My tii has an Alpina 5 speed wth a dogleg first, I have to use this procedure in every gear. Will rebuild some day, just driving a crash box until then.
Good luck

Joe Bob · Joe Bob's Garage

If I recall....914 trannies have 901 useable parts.

Matt Monson · 11-27-2010, 05:56 AM

First and reverse should only ever be engaged when the vehicle is completely stopped.

The design and function of the 901 gearbox is archaic and they cannot be shifted quickly. The description of 2nd and 3rd gear shifting sounds normal, as does the function of 1st and reverse. I'm not convinced that there is really anything wrong with the gearbox and suspect that it may be more a matter of learning the proper technique for driving a 40 year old car.

J P Stein · 11-27-2010, 07:18 AM

Quote:

Originally Posted by Matt Monson

First and reverse should only ever be engaged when the vehicle is completely stopped.

The design and function of the 901 gearbox is archaic and they cannot be shifted quickly. The description of 2nd and 3rd gear shifting sounds normal, as does the function of 1st and reverse. I'm not convinced that there is really anything wrong with the gearbox and suspect that it may be more a matter of learning the proper technique for driving a 40 year old car.

Matt:
A properly set up and adjusted 901 can be shifter into 1st gear at any speed you have the guts (& valve springs) for....not quickly but positively(some mechanical sympathy is required for longevity

). If not, the above conditions have not met. My 914 trans was done by one (if not the) best in the business and did the trick as long as I owned it (12 years). Perpetuations of internet mis-information does us no service.