I need to depress the clutch pedal twice to get the 901 into 1st....

[svonkampen]

Hi all,

I need to depress the clutch pedal twice to get the 901 tranny into 1st gear,

My mech says this is kinda normal on 901's........I don't believe him......
I know Porsches aren't known for great shifting but surely a well-tuned 901 should shift a lot better than this.........To recap......

I get to the stoplight, put her in neutral, then while clutch pedal is down I try to shift into first but to no avail........But, if I go back to neutral and then double tap the clutch, then she'll go to first

What gives??

[steveW]

Your'e lucky!


Ican't get first unles I'm stationery..................dead stop!!!!

[svonkampen]

Ok .......

But is this "normal"? In other words did 901 trannies exhibit these same idiosyncracies when new??

SvK

[svonkampen]

Steve....

It's the same for me......Only when stationary.......Again, will a rebuild fix this or is it totally normal?

SvK

[steveW]

svonkampen............dunno, mine was over 30-yrs old when I got it free with an original 71 'T'.............

[svonkampen]

Steve

thanx....

let's find out. I started a new thread

[Grady Clay]

SvK,

That may be a sign of some oil on the clutch disc, usually from a slightly leaking inputshaft seal.

Best,
Grady

[svonkampen]

hmmmmm

[Grady Clay]

Hmmmmm,

I suppose I should post more explanation of my proposed diagnosis.

When the input shaft seal just leaks a tiny amount or it just first starts to leak, the oil goes down the clutch release bearing guide tube into the side of the disc closest to the transmission. This oil tends to “glue” that side of the disc to the pressure plate friction surface. The other side of the disc (toward the flywheel) is still operating normally.
With this situation the clutch is not releasing and the “oil glue” overpowers the syncro. This either (with good syncros) prevents the sliding sleeve from engaging the first gear dogs or (with not perfect syncros) causes the engagement dogs to “grind” after having overpowered the syncro friction.

Operating the clutch several times sometimes releases the stuck disc and everything appears normal for a while. This is usually a progressive situation and severely damages syncros, sliding sleeves, and gear engagement dogs. It can lead to expensive transmission repair.

This is difficult to diagnose initially because there isn’t any oil leaking from the clutch area.


Are there other possible causes of your symptoms? You bet.

A progressive failure of the clutch cable or linkage. Usually you notice increasing clutch free play.

The clutch release bearing sticking on the guide tube. When you depress the clutch pedal, you just stretch the cable, etc. and not fully release the clutch.

A broken pressure plate spring where the TO bearing initially only actuates part of the PP.

There are probably a dozen other possible causes.



SO, Hummmm

Best,
Grady

[svonkampen]

Grady......

The world would be a better place if every problem had 1 cause and 1 solution......Then again that would take away the mystery!!!!

Thanx for elaborating, I will check out the input shaft leak possibility.

SvK

[Early_S_Man]

SvK,

Of course, it could be a sticking clutch disk as Grady described ... but there would also be another annoyance accompanying your 1st gear problem, as in a grinding everytime you try to shift into reverse.

If reverse grinds, then you have one trail to follow to fix both problems ... a complete rebuild!

If the ONLY current problem is having to double-clutch to get into 1st gear ... then I believe you have the 'classic' case of a worn-out 1st gear synchronizer!

[svonkampen]

no grinding in reverse.....my gears very rarely grind at all....only if i nick reverse

[nostatic]

what happens if you shift into neutral at a stop, then when the light turns green, you depress the clutch, move the shift lever up towards second (not all the way into gear though), pause for a tick, then pull it into first? I do this as a matter of course to "quiet" the syncros before putting it into first.

[svonkampen]

brb ....i'm gonna try it....

svK

[ubiquity0]

Originally posted by nostatic
what happens if you shift into neutral at a stop, then when the light turns green, you depress the clutch, move the shift lever up towards second (not all the way into gear though), pause for a tick, then pull it into first? I do this as a matter of course to "quiet" the syncros before putting it into first.

He has a 901. He's gonna get carpal tunnel syndrome with all that doglegging

[svonkampen]

NoStatic,

You're right......goin to 2nd has the same effect as double clutchin'....

SvK

[Grady Clay]

The symptom you posted that suggested this cause was:

“I get to the stoplight, put her in neutral, then while clutch pedal is down I try to shift into first but to no avail........But, if I go back to neutral and then double tap the clutch, then she'll go to first”

As Warren suggests, if it grinds when going into reverse when at a complete stop is a sigh of a clutch not releasing.

There is another potential cause for not going into first at a stop and I may have mistakenly assumed you knew. The two parts of the transmission must be moving with respect to each other for the sleeve to slide over the syncro and engage the gear dogs. When both parts are stationary, the dogs can just “butt up against” each other and fail to engage. This is particularly true with damaged dogs. When you let the clutch out, you spin the input gear parts so when you attempt to engage the dogs it is spinning relative to the stationary pinion gear parts. Presto, it engages.


Here are some tests to perform:

- 1) Come to a stop and leave it in whatever gear and just depress the clutch and keep it depressed. Pause for a few seconds. Take it out of gear, clutch still depressed, and wait a couple of seconds. Now try to put it in reverse. If it grinds, the clutch isn’t fully releasing for whatever reason.

- 2) Come to a stop and put it in neutral and let the clutch out. Depress the clutch and attempt to put it in 5th. There should be little resistance. If it balks at going into 5th, try reverse. If it grinds, the clutch isn’t fully releasing.

- 3) Try downshifting into 1st from 2nd at a slow speed. How well does it synchronize?

- 4) While you are at a stop and it is in reverse and clutch fully depressed, move to neutral, pause and try and engage 1st gear. What result?

- 5) While you are at a stop and it is in 1st and the clutch is fully depressed, move to neutral, pause and try to engage reverse. What result?

- 6) If you are on a slight incline (up or down) and allow the 911 to roll slightly, does the problem persist?

- 7) Are your symptoms temperature dependent? Better or worse as things heat up.

- 8) how much free play do you have? Say percent of total pedal travel.


Most problems have a solution. How quickly can you find it?

Best,
Grady