1600 4-speed to 2002 4-speed swap question

[autokunst]

The problem with my question is that I'm not entirely sure what I am asking.  But I trust that folks on the forum will read between the lines and hopefully steer me in the right direction.

 

My 1968 1600-2 falls into the top secret, voodoo category of "early 1600 cars", and has those funky bits and pieces that all the rest of the 02s do not have.  I love this, but it makes for difficult searches when looking for info sometimes.  I recently swapped my original 4.11 long neck diff with a 3.64 long neck diff from a 1968 2002.  Despite the higher gearing and lower torque/power of the 1600 engine, I love the combination.  When I did that swap, I needed to use the 3-bolt flange from my 4.11 diff on the 3.64 diff because came to me with a 4-bolt flange.  I was surprised at this given they were both '68,but that's what I have.

 

My 4-speed transmission is in need of work.  It does not like going into 1st gear, and 2nd isn't a picnic either.  I was preparing to send it out for work when I learned a friend has a 4-speed transmission and driveshaft from their '73 2002.  Relatively low mileage, no noises, easy shifting.  This would be a much more cost effective "solution" to my transmission issues than rebuilding the original.  

 

I can put the 4-bolt flange back on the diff to mate with his 4-bolt driveshaft.  However, the driveshaft will still be too long because the '73 had the short neck diff.  So my question: is the solution to use his driveshaft but have it shortened (and balanced) to fit with the long neck diff?  Or do the drive shaft halves work such that I can use the front piece from one DS and the rear piece from the other, thus creating a 4-bolt/3-bolt Frankenstein shaft?  Is that even a thing?  I don't have the parts here in front of me, so I can't try fitting the square pegs into the round holes yet. 

 

Any other bogies I should look out for?  I appreciate your input!

[Son of Marty]

Do not mix d/s parts with out clocking and balancing them as a unit, keep your d/s and diff you'll need to convert between the hydraulic clutch and the mechanical one.

[Preyupy]

The early 1600 driveshaft uses 3 guibo couplings so you can’t swap pieces from the 2 driveshafts to make 1 even if you have them shortened and balanced.  The pinion on the differential has a pilot for the rear Guibo so you can’t just bolt a flange from a short neck diff to your long neck diff and use the standard 4 bolt driveline flange and use a modified (‘73) driveline.  
 

The output splines on the ‘73 transmission are fine spline and the early ‘68 transmission is a course spline so you can’t use the output flange from the ‘68 trans on the ‘73 and keep the old driveline.  
 

About the only way to do it is have a driveline shop take the 4 bolt flange off the front of the ‘73 driveline and put it on the ‘68 driveline and balance the assembly.  Thus you will have the Frankenstein driveshaft. 

[Alexander]

 

27 minutes ago, Preyupy said:

The output splines on the ‘73 transmission are fine spline and the early ‘68 transmission is a course spline so you can’t use the output flange from the ‘68 trans on the ‘73 and keep the old driveline.  

 

This is the main reason you can't simply swap the drive flange on the trans. I think it was during 1973 that BMW went with the fine spline on the trans output shaft. Earlier 2002 transmissions had coarse spline. They changed to fine splines because the extra torque of the 2.0L wore out the coarse splines. It is the extra torque of the 2.0L that also necessitated BMW to redesign their driveshaft for the 2002 in 1968, which is rated for higher torque. This new redesigned driveshaft was the shorter style coupled to a 3.64 long neck diff. It was only used for about a year and a half into mid-69 before BMW switched to the short neck. The 1968 2002 driveshaft ditched the three rubber guibos of the 1600-2 and the 3 hole flanges in favor of 4 hole flanges and u-joints. That's why your 1968 3.64 long neck diff from the 68 2002 came equipped with 4 hole flange.

 

The solution:

 

If you want to use the 4 speed from the 73 2002 with your 68 2002 3.64 long neck diff, you need to get a hold of the 68 2002 driveshaft because it will mate to the 4 hole flange. In the process, put back the 4 hole flange you swapped for the 3 hole on your 3.64 long neck.

 

Or, you can get that 1600 trans rebuilt. But, it uses smooth Porsche synchros. And, they are expensive. You will most likely need to replace the ones on 1st and 2nd gear. In this scenario you will use your 1600 driveshaft.

[Tommy]

Your -68 1600 is also with mechanical clutch - right? -73 is hydraulic.

Would mechanical clutch setup work with a -73 tranny?  I thought it wouldn't but by looking some pictures it might?

[Conserv]

4 hours ago, Alexander said:

 

… If you want to use the 4 speed from the 73 2002 with your 68 2002 3.64 long neck diff, you need to get a hold of the 68 2002 driveshaft because it will mate to the 4 hole flange. In the process, put back the 4 hole flange you swapped for the 3 hole on your 3.64 long neck…

 

+1

 

It’s a narrow window: 2002’s were only manufactured with the long-neck differential from, roughly, January 1968 until January 1969. But you already found a rare-bird long-neck 3.64 and owners continue to swap out long necks for short necks. Get a Want-to-Buy ad up on this forum ASAP, before another person sends their 2002 long-neck driveshaft to the recycler! 😯

 

Good luck!

 

Steve

 

 

 

[autokunst]

Thanks to everyone for the great and consistent feedback.  I know that I have a mechanical clutch in the car, and I understand that the '73 would have had a hydraulic clutch setup.  I want to stay with the mechanical system - but have not researched what any of that means yet.  I had assumed that my mechanical pedal and cable setup, along with the clutch (or a replacement while I'm in there) would simply transfer over to the newer transmission.  Is that a correct assumption, or are there factors that make that difficult/undoable (frankenclutch)?

 

If I am deciphering the comments correctly, and exclusive of the clutch situation which I have yet to understand, I feel my two viable options are:

Option 1 - Just rebuild my transmission at cost, and use the current driveshaft.  Live happily ever after.

Option 2 - Try to find a 1968 2002 driveshaft and use that along with the '73 transmission.  I am assuming that the 4-bolt flange pattern is the same at the front of the '68 drive shaft and the back of the '73 trans.  Yes?  I assume this may involve a new, later center bearing?  Or a rare '68 2002 center bearing?

 

I will begin a search on the clutch topic so I can learn more about what I don't know on that.

Thank you!

[Alexander]

1 hour ago, autokunst said:

I had assumed that my mechanical pedal and cable setup, along with the clutch (or a replacement while I'm in there) would simply transfer over to the newer transmission.  Is that a correct assumption, or are there factors that make that difficult/undoable (frankenclutch)?

 

If I am deciphering the comments correctly, and exclusive of the clutch situation which I have yet to understand, I feel my two viable options are:

Option 1 - Just rebuild my transmission at cost, and use the current driveshaft.  Live happily ever after.

Option 2 - Try to find a 1968 2002 driveshaft and use that along with the '73 transmission.  I am assuming that the 4-bolt flange pattern is the same at the front of the '68 drive shaft and the back of the '73 trans.  Yes?  I assume this may involve a new, later center bearing?  Or a rare '68 2002 center bearing?

 

Don't worry about the clutch. All four speed 02 transmissions can be used with either a mechanical or hydraulic clutch. They all have a provision to mount either a hydraulic slave or mechanical clutch. Most early 68 2002s were equipped with a hydraulic clutch.

 

Yes, all 4 bolt flange patters on the 02s are the same.

 

And, all center bearings for all 1600-2 and 2002 driveshafts are the same. Just make sure you get a factory center bearing as the after market stuff is junk.

 

 

[autokunst]

52 minutes ago, Alexander said:

Don't worry about the clutch.

Thank you for that confirmation!!!  I have posted a WTB for the correct drive shaft.  Fingers crossed I can save one from salvage.

[autokunst]

I found a driveshaft local to me, but it is for a 1969 2002 with automatic transmission.  I know this is definitely the wrong part, but how wrong is it?  Rebuildable to fit?  Perhaps that is too hasty.  I will keep looking for the correct one...

[Mike Self]

15 hours ago, Preyupy said:

The output splines on the ‘73 transmission are fine spline

From unfortunate experience I found the factory didn't switch to fine splines on the tranny's output shaft until early 1974.  My Dec 72 build '73 had coarse splines, and (apparently, according to the dealer's service bulletins) the flange was poorly heat treated and/or the nut wasn't properly torqued, and the shaft ate the splines on the flange, damaging themselves in the interim, so I had to have both replaced--with a fine thread shaft and flange, of course. 

 

That's a small relief to your driveshaft problem, but you might want to check yours to make sure.

 

mike

[Alexander]

On 8/11/2023 at 9:40 AM, autokunst said:

I found a driveshaft local to me, but it is for a 1969 2002 with automatic transmission.  I know this is definitely the wrong part, but how wrong is it?  Rebuildable to fit?  Perhaps that is too hasty.  I will keep looking for the correct one...

When I said all 2002s use the same 4 hole output flange pattern I wasn't thinking about the automatic. I have no experience with the driveshaft for the automatic. And, I doubt it would fit your application. Maybe somebody here can weigh in. Did they even make the automatic at the time when the 2002s were equipped with the long neck ? And, even if this is the case, the auto driveshaft will probably not fit.

Edited August 13, 2023 by Alexander

[Peter Zettler]

I have a 1602 with a long neck rear end. The drive shaft is from an automatic.The trany is from a 2002 with a corse splines 4 hole flange, the rear flange is a u joint. The 2 quibos ( 4 hole)are for an automatic ( you can't get the flat 4 hole type any more). The automatics are to thick. You have to grind them flat and then they work. I've been driving this combo for 27 years. Peter Z

[Peter Zettler]

You might check the shift stick. Grease it. They get dry over the years and make for a hard shift, particularly into first gear. Peter Z

[Conserv]