901 Trans Question

[69T]

Hello all, i have a 1969 911T with the 901 5Spd, my trans has been getting graunchy and I have purchased another trans out of a 1971. Are they interchangeable? can I mix and match parts to make it work? or should I try to upgrade to the later style clutch? Also any have any idea of the Crownwheel Bolt Torque? cheers, Craig

[davidppp]

Hello there.

The trans are very similar inside.

But it is hardly economic to destroy a good 2.2 (911)tranny to make one good 901.
Especially as the same parts will anyway be worn, and although marginally usable, will not last long enough to be worth the labour..

better to buy the parts needed.

usually synchro rings, and maybe dog teeth and sliders..the sooner you do the work,the less damage..



Kind regards
David

[69T]

Hi david thanks for the reply, I am buying new parts for the Trans I am working on ,that way i can pop out the one that is in it and install my reshly rebuilt one. its more the clutch actuating sysytem and clutch parts i am concerned with are they interchangeable? cheers, Craig

[Grady Clay]

69T,

Welcome to the Forum. You will find much good advice here.

First, what is wrong with your ’69 transmission?

What is your intended use for your 911 – daily, occasional, track events, other?

What is the 911’s history?

Look under the differential area and report the S/N and transmission type.

The transmissions ’69 and ’71 share similar internals but are not directly interchangeable. As you noticed, it is the clutch actuating mechanism that is the significant difference. Unless you are willing to go to a lot of work, you are best served rebuilding your original ’69 transmission.

One of the other differences is gearing. The ’69 has gear ratios that are far more fun and easy to drive. Post the numbers from both transmissions and we can probably tell you what you have.


Again, welcome. Please post some images of your 911 and the 901 & 911 transmissions. Gather the information before you do anything.

Best,
Grady

PS, if you need help posting images, e-mail me at gradyclay@hotmail.com
G.

[69T]

Hello Grady, thanks for the info the numbers on the transmission are 901/13 and 7193124. I hope this helps to identify it for me. cheers, Craig

[Grady Clay]

Craig,

Your 901/13 is the late ’69 901 transmission with the pressure die cast housing (called “investment” casting from the German translation – also indicating the great cost investment in the tooling).

It is geared:

1st A 11:34=3.09:1
2nd F 18:34=1.89:1
3rd M 22:29=1.32:1
4th S 25:26=1.04:1
5th Z 29:23=0.79:1
with a 7:31 ring & pinion

The S/N is consistent with everything else.

Please check to see if there are any other numbers.

This was equipped with the “simplified differential” and you should confirm it has been updated. Do a Pelican search on “simplified differential” and don’t neglect this – bad things can happen.

How about the other questions?
The more info, the better we can help.

Best,
Grady

[Grady Clay]

Here is the gear chart for the 901/13.
It is the same as 901/02
“
"
© Dr. –Ing. h.c. F. Porsche A.G.

Best,
Grady

[69T]

Hi Grady, Thanks for the info. So I would think then that the Trans in my car should be the same as the one on the bench! The simplified Diff i will read through the info and talk to my Mechanic and see if it has been updated or not. I will keep you posted, what do you think of those Weltmeister Shift lockout spring kits? as well as the Shifter set up tool. cheers, Craig

[Grady Clay]

Craig,

NO, the 911/01 on your bench is significantly different from the 901/13 in your 911. The most important are the gear ratios and the clutch actuation. I wouldn’t fit the 911/01 to your 911 unless you converted to the 225 mm pull-type clutch. Even then, I would change the gears from your 901/13 into the 911/01. Probably both transmissions have the “simplified differential” issue.

I realize you have a 911/01 on your bench and that you want to be able to do an in-and-out swap in a weekend. There are some serious reasons why this is inadvisable. Let’s find you another 901/13, get it serviced and then you can have a successful swap weekend.

The other option is to rebuild your 901/13 in a weekend. Are there Porsche friends that can help you? I can do this repair between track sessions; it isn’t difficult if you are prepared.

The raison d’etra for a Type 911 is to use the 225 mm clutch.

Again,
How about answering the other questions?
The more info, the better we can help.

Best,
Grady

[69T]

Hi Grady, I am confused I have a 901/13 on the bench that we have all apart. Should i look for the numbers on the trans in the car? I am using it for street driving and eventual autocrossing. cheers, Craig. Oh and I love it!!

[69T]

Hi Grady, I apreciate your help on this as I dont want to assemble a transmission and then not have it fit in my car. So to summarise I have a 901/13 apart on my workbench(i havent looked at the numbers on the transmission in my car). Which will not work in my car and I should recondition the 5Spd in my car now.What should I do with the trans spent $900.00 USD on? Assemble and sell it? or use it for spares?please let me know. Cheers, Craig

[Grady Clay]

Craig,

Let’s get everything straight.

1) The car is a ‘69T. Is it original?

2) The trans on your bench is a 901/13 S/N 7193124 and you have it apart. These are ’69 transmission numbers, not a ’71 set of numbers.

3) You have another transmission purchased out of a ’71.

4) You have your transmission still in the ‘69T.

I still don’t understand.
Was the 901/13 S/N 7193124 sold to you as a ’71?


Back to my prior questions:
What is wrong with the transmission in the car? I don’t understand graunchy.
What is the Type # and S/N of the transmission in the car?

Can you post images of the transmissions?
What is the clutch pivot on 7193124?
What is the inside diameter (ID) of the support ring on the differential cover of 7193124?

Once we get the communication straight we can have fun with the transmission(s).

Best,
Grady

[Grady Clay]

BUMP

I hope I didn’t offend by asking clarifying questions. None intended.

Best,
Grady

[69T]

No not at all, I thought you had given up on me!! the trans on the bench is the one i have given you numbers for. I thought it was out of a 1971, I will take pics of the areas you mentioned and send them to you. I still have the original trans in my car ,, i will get the numbers off that trans and send them to you as well. As far as I know the trans in my car is the original one.It is noisy and rumbly and hard to shift into ist and I keep almost hitting reverse, when I shift into second.I bought the car from Bill Kelley who has been great to me and I was very happy with the car when I bought it. He bought it through Dave B at TRE, they are the ones that said the car needed trans work, which agree with now that I have driven it for a year. it also needs linkage bushes badly.Once I get these numbers and pics you can help my Newbie self to shifting happiness!! cheers, Craig

[Grady Clay]

Yea!

You may have lucked out – big time. If the transmission on the bench is a 901/13 and un-modified to fit a ’71, then you have an easy direct replacement for the trans in your ’69 911, regardless of Type. Even if it had been modified from ’69 to ’71, it should be easy to return it to original.

Major progress is made here.

The communication issue can be improved by writing in complete sentences and re-reading your post. I write everything in MS Word.doc format with the spell check and grammar check. I then copy/paste to Pelican. I think my misunderstanding you was from cryptic posting. Lame o’l me isn’t very internet lingo savvy. King’s English (Brit or American) works well for me.


OK, now to play time.

Count the teeth on the gear pairs. They are represented as {(input shaft teeth) : (pinion shaft teeth)}. Each gear should be marked. Check here, report what you find.

“…noisy and rumbly….” usually indicates a failing intermediate plate 4-point bearing. This is not uncommon with 901 & 911 transmissions. Those two bearings should be replaces every time the transmission is serviced. Yes, they are expensive but they were failing within warranty when close to new.

The shifting issues are not unusual and can be fixed with new syncros, engagement dogs, sliding sleeves and related parts. This is regular long-term maintenance for 901, 911 and 915 transmissions – similar to brakes and clutches. These are friction wear parts. It also sounds like you need some simple shift linkage bushings for a start.

Do you have the differential out? Does it have the “Simplified Differential” up-date?

Dave, Tyson and the TRE crew can repair this for you also. They certainly have the skill and inclination to do it right. Many others are there to help also.

If you DIY; Pelican Parts, TRE and others can help supply parts. This Forum can provide information and guidance.


Now it is your turn to report. HeHe.

Best,
Grady

[69T]

Hello Grady, Well I have a had a good look and talk with my mechanic and i am now pretty confident that the trans I have(that I bought and is apart on the bench), according to the numbers(901/13) (7193124) (901.301.301.0R) and to the clutch release bearing and the fork, as well as the 7:31 Crown wheel and pinion and the 190mm inside diameter of the diff support ring.Is the '69 trans that should fit my car. It is in pretty reasonable shape, with very little wear evident on any of the bearings , gears etc. It does have the Simplified differential tht you speak of. The bolts that run thru the side flanges are worn at the little nubs at the end. Is the problem that the little nubs break off and then the shaft comes out? Is a rollpin drilled at another location enough to ensure it is not going to fail? or should i try to find the parts to convert it to the 914 style diff? where can I get those bits? Do I need to buy the shift tool that pelican sells to set up the gears properly? Should I get one of those Weltmesiter Lockout spring kits, that prevents from hitting reverse accidentaly? Cheers, Craig p.S I have a couple of pics too.

[Grady Clay]

Well I have a had a good look and talk with my mechanic and I am now pretty confident that the trans I have(that I bought and is apart on the bench), according to the numbers(901/13) (7193124) (901.301.301.0R) and to the clutch release bearing and the fork, as well as the 7:31 Crown wheel and pinion and the 190mm inside diameter of the diff support ring. Is the '69 trans that should fit my car. It is in pretty reasonable shape, with very little wear evident on any of the bearings , gears etc.
Good

It does have the Simplified differential that you speak of. The bolts that run thru the side flanges are worn at the little nubs at the end. Is the problem that the little nubs break off and then the shaft comes out?
Yes. It then destroys the transmission.

Is a rollpin drilled at another location enough to ensure it is not going to fail?
or should i try to find the parts to convert it to the 914 style diff?
Use the 914 parts. It is only a few parts inside the differential, not the differential itself. Do not try and drill and install a roll pin like the late 915 transmissions. Your differential steel casting won’t take that.

Where can I get those bits?
Post a WTB on Pelican classifieds

Do I need to buy the shift tool that pelican sells to set up the gears properly?
Try borrowing one

Should I get one of those Weltmesiter Lockout spring kits, that prevents from hitting reverse accidentaly?
You may only need some bushings and a lock-out plate. You may also need to repair your shift handle and shifter housing.


The rumbling in the trans in your 911 is most likely the 4-point ball bearing in the intermediate plate. If it is with road speed and not engine speed, it probably is the large pinion bearing.


What are your plans for refreshing the 901/13 on the bench?

At a minimum I would replace the two intermediate plate bearings and the necessary syncros, sliding sleeves and gear dogs. Of course new gaskets and seals. Careful inspection with a knowledgeable eye is essential. A “dam seal” in a modified clutch release (TO) bearing guide tube is worthwhile. Replace the two plastic bushings at the throttle bell-crank. A new ground strap is appropriate.

What is the condition of the speedometer drive? Install the better of the two in your 911, keep the other as spare. This is the time to replace the clutch cable and make sure you have the metal “plastic piece” where the cable connects to the clutch arm.

Since this is a magnesium casting you should carefully clean it and coat with Tectyl. PelicanParts is working a deal to supply that.

When you pull the engine, you should be prepared to replace the clutch and flywheel if necessary.

You are going to need at least 8 new M10 CV bolts and Schnorr washers. Carefully inspect your CVs and boots. You may want to clean, re-grease and replace the boots while you have the transmission out.

Another source of road speed “rumble” can be a rear wheel bearing. Make sure that isn’t your problem before you go working on the transmission.

Best,
Grady