69 912 901 5-spd into 71 911 T ?

[Greg Otto]

What should I consider if swapping a 901 5-speed from a 69 912 into my 71 911T? Assuming everything is stock, I wonder about the gear ratios, shifting and clutch mechanisms, etc. Also, what would be a fair price to offer for a supposedly good 90K mi. original, undocumented gearbox? Any way to do a bench test?
Thanks in advance.
Greg

[jluetjen]

I would expect the gear ratios to be fine as is off the top of my head since both engines have roughly similar rev ranges. The big issue will be the flywheel, clutch and clutch release mechanism -- they are completely different from 1969 to 1970. I believe that the shifting mechanism is the same. You should be able to get the parts needed to make the change from your favorite used 911 parts supplier.

As far as a price for a transaxle, I assume that you mean a 911 style box from '70 or '71. I'd say $150 - $200. If you're going to pay more then that I'd want to test-drive it to ensure that it is as good as that, or else it should be recently rebuilt by a reputable shop with receipts and verification.

[jpnovak]

example price point. I paid $50 for an undocumented 69 901 5 sp.

John is right. It should work fine but you will need a new flywheel, clutch assembly and cable. Up to 69 had a 215mm flywheel and the 70-up used a 225 mm flywheel.

[Bobboloo]

The clutch, pressure plate and flywheel are different between the two cars. The 69' used the push type pressure plate so I think your best bet would be to get a 901 pressure plate, clutch and flywheel.

Otherwise the only other way would to be to use the 71' forklift with the 69' tranny but I don't think that's possible.

The gear ratios are probably fine. Maybe someone can chime in on that.

As far as price. I would say a good used tranny is worth $150 to $450.

I recently sold an undocumented 915 for $500 that was supposedly rebuilt. It was indeed a good tranny as it turns out but without paper work I felt that $500 was tops.

[TimT]

The cases are different between '69 and '70. The '70 has a small extra boss cast onto it to for the termination of the clutch cable. The '70 case also has a bracket on called a clutch cableguide tube or something

the clutch fork pivot points are slightly different also..

[Grady Clay]

Greg,

Why do you want to make a change? Is there something wrong with your transmission?

John is correct as to pricing, just don’t expect a new transmission. Plan on a proper rebuild. You will enjoy the results for many years. Now is also the time to clean, inspect, and replace clutch parts as necessary. At least replace the disc, release bearing, and pilot bearing.

John is correct, the gears are closer. In fact I think they are more desirable because they are slightly shorter ratios in the 2-3-4-5 positions. An X 5th is readily available and might be something to consider.
Your ’71 probably has gears A-GA-O-V-ZA.
The ’69 probably has A-F-M-S-Z

A = 11:34
F = 18:34
GA = 18:32
M = 22:29
O = 23:28
S = 25:26
V = 27:25
X = 28:24
Z = 29:23
ZA = 29:22

They both should have a 7:31 R&P.
Find the serial numbers and Type numbers of both transmissions. That will help with the gear ratios.


Agree on a price subject to inspection.
Have the seller take it to JWW or other for inspection.
John will be able to diagnose any problems and give you an idea of cost and if it is a worthwhile purchase.
You can do the conversion to a pull-type clutch yourself or have John do it.

I’m assuming it is a mag case.

You will need:
The longer clutch release bearing guide tube.
Reposition the arm pivot and install the 2.2 arm and parts.
A new good used differential side cover. This will require resetting the differential bearing pre-load and setting the R&P clearance.
The termination for the inner cable in the clutch cable assembly will only have a “V” in the casting. You will need to machine this to fit the restraining piece.

Of course, you want new seals and gaskets.

The “while you are there issues” are:
Syncros and sliding sleeves. 1st and 2nd need to be like new. Possibility 3-4-5 only need to be turned. I would recommend you upgrade the syncro bands and stops.
The ball bearings in the intermediate plate are subject to failure. Now would be a good time to summarily replace them even if they appear OK.

If it is an aluminum casting, you will have to custom fabricate the support for the clutch cable at the side of the transmission just under the axle and the tremination for the inner cable. Not too difficult and can be better than the original ’70-’71.


Here are some informative links:
’70-’71 clutch
clutch cable for 70-71 901
and
'70-71 T.O. arm play?
and
http://forums.pelicanparts.com/porsche-911-technical-forum/166598-clutch-cable-70-71-901-a-post1520882.html#post1520882
“How to ID a Type 911 transmission”
How to ID a 911 ty[e transmission tranny
“Moving the clutch lever pivot ball”
Moving the clutch lever pivot ball


Best,
Grady

[Greg Otto]

Wow!! I appreciate all the responses. Sorry, I should have mentioned in my original post that the reason I'm considering this is that my 71 901 needs a rebuild. I thought that with using the 71 clutch assembly. etc. this might be a quick, cheap, easy temporary fix. However, that does not seem to be the case. Looks like I'll just pull the gearbox and have JWW take a peek for a proper diagnosis and go from there.
Greg

[randywebb]

Rebuild your box or look for another 911 type. Swapping any 901 into a 1970-71 911 is very difficult because you do NOT have a 901. This is a common misunderstanding. Your box is a 911 type and uses entirely different CV joints and drive flanges. I found no easy way to use a 901 in this application -- it would take a machinist to do this right. I only have a sample size of 3, so it might be that somewhere there is a 901 with the later flanges, or a '71 car with the earlier ones....

And how do you know that a used 901 will be in better shape than yours?

[Grady Clay]

Greg,

Read up on the subject; read the above links, search on Pelican, read Bruce Anderson’s book, and continue the discussion here. There is a lot to share with Pelicans that have 901/911 transmissions.

You might still consider buying the 901 just for spare parts and gears. I’m sure JW will take what you don’t need.

A 901/911 is an exceedingly easy transmission for a DIY project. With this Forum, you should be just fine.

Randy is correct; a Type 901 transmission is aluminum case ’63-’69 and a Type 911 is ’70-’71. There is some question in my mind about something interim in ’69.

Randy, actually a ’69 is a direct interchange as far as the axle flanges go. There are several peculiar ’69 only flange configurations. I think there are the big flanges for a “simplified” differential in an aluminum case, for a “simplified” differential in a mag case, and for the LSD in a mag case – all different.
The clutch linkage is the BIG issue.

I’m convinced there are both mag case ’69 transmissions and aluminum case ’69 transmissions. Who can offer S/N and Type info?

Best,
Grady

[Raynald]

Hello All !
I want to know ... If I have a 901 1969 transmission and I want to upgrade the engine to 3.0L I will need a special flywheel with ring gear on to fix to the engine or not the standard 3.0 flywheel ?
Thanks
Ray

[Grady Clay]

Ray,

You can use most of the 3.0 clutch pressure plate, ring gear, and flywheel but you will need a 2.2 disc and release bearing.

You will have the same issue as Randy with fitting a ’69 Type 901 transmission to a pull-type clutch. It is much easier to use a ’70-’71 Type 911 transmission or a '72-->915.

Best,
Grady

[randywebb]

"direct interchange as far as the axle flanges go."

OK, I only had a sample size of 1 - and it was a definite no go.

PS - I udpated the old thread on this issue, and cross-posted to the Wayne tranny book thing. Since Wayne is in California, I expect to see some pics of human "trannies" when the book comes out.

[Grady Clay]

Randy,

What transmission was a “No Go”?

BTW, you have e-mail.

Best,
Grady

[randywebb]

The 901 I paid for. I'll look up the info on it....

OK, 901 transmission # 1283020, type 902/02 -- no way to get it to match into a later style car as detailed in the other thread I posted on today.

[jluetjen]

The trick to making the axle flanges work is to take 1 mm off of the diameter of the later flanges. I did that and have been using some 915 flanges in my aluminum 901 transaxle.

[Grady Clay]

Randy,

1283020 is a 5-speed transmission number for a ’68 912 USA version special order, ROW (inland) standard

That 902/02 is a ’68 5-speed 912 transmission (simplified differential) and uses the early 6-bolt smaller Lobro CV diameter (and a short axle). A ’69 trans has the larger 4-bolt, 2-pin CVs, same as ’70 and later. In ’72 they made the CV thinner but maintained the large diameter and 4-bolt, 2-pin arrangement. Even when Porsche went back to the smaller 6-bolt CV, the big ones were used with the Turbos.

Keep the big CVs clean and greased and they last forever, even with big engines.

Can others chime in about the ‘69s?

Best,
Grady

[randywebb]

So can we say that a '69 will always fit with the 1970 and later cars?

BTW, that was sold to me as a '69 - looks like another misrepresentation from that shop....

[Grady Clay]

Randy,

No, a ’69 won’t directly fit a ’70 and later without all the trivia listed above.
If you want to use a smaller 215 mm push type clutch (2.0 ’69 and earlier) instead of the 225 mm pull type clutch (’70-’89), then yes, it will fit.
My point was the AXLES will fit.

None of this is an issue with the ’68 902/02 you were sold as a ‘69. It would be a lot of work to fit that to a ’70-‘71 using the 225 mm pull type clutch – not impossible but a LOT of work.

Best,
Grady