Upgrading to a 5-Speed transmission

Source: CS REGISTER Jan/Mar 1996
Edited & Posted by Art Wegweiser   

CS Coupe - 5 Speed Conversion - Carl O. Nelson- BMW Independent, La Jolla, CA

Many times in the past I have been asked about the difficulty of installing a later model 5 Speed transmission into the older CS automobiles. At our shop we perform this conversion every other week. The limiting factor is the availability of suitable five speed transmissions. If your old automatic transmission has died or is about to, now is the time to consider its replacement by a manual version. The great news is that the CS has been drilled to accept almost any transmission used by BMW. The determining factor (other than the size of your wallet) is the presence of a mechanical speedometer drive. It is possible to modify an 82 and later gearboxes to work with an older type speedometer, but it is not worth the effort. Any of the large 6 cylinder five speeds, before 1982, will fit and drive the speedometer. The speedometer drive is the same for either four or five speed, but the auto drive unit will not fit. Be certain to get the drive as it costs a fair bit. I recommend the overdrive 5 speed out of the 528i; a close ratio (1:1 fifth) has the same external dimensions. This was a common gearboxes in Euro cars, but it is not as durable as the overdrive, also the reduction in noise and wear is not gained. I have found the sport box (close ratio) to be a poor choice as most big block 6 cylinder cars have lots of torque and don't really need a close ratio box. In addition we have had really bad luck with the c/r 5 box (the lay bearings fail and the gear set is usually in bad shape ** really noisy**).

The conversion is not cheap. There are many pieces involved, but everything is straight forward, and the ability to shift into fifth at speed is awesome, not to mention the reduction in the wear on the engine and the reduced noise level in the passenger compartment is worth every dime. In my own cars I have over logged more than 150,000 miles on these conversions. They are reliable and tested. The transmission is one of the most durable ever used by BMW. We have probably installed or sold as a package 100 of these units. READ don't be shy. It works. I will describe the process and at the end list the components.

The five-speed conversion for a CS is not difficult, but there are a great number of steps. The layperson might not immediately understand some of these steps, but they have a reason.

1. Remove the exhaust system (you need lots of room) up to the exhaust manifolds.

2. Remove the drive shaft. A custom unit must be fabricated, shorten a 4 speed by 3.75 inches or lengthen an automatic .75 inches, replace u-joints as necessary, replace center carrier bearing and renew hardy disc. This is custom work and very few shops can do it.

3. Remove transmission and shifter assembly (be sure to disconnect the reverse light switch). An automatic is a pain here, remove the bolts gearboxes to engine and flywheel to torque converter. This is a heavy unit use a jack to support and drop. The four speed is quite easy to remove. Separate the gearboxes from the bell housing (four 19mm nuts), free the clutch throw-out fork retainer spring and extract the trans. Remove the bell housing and clutch slave cylinder. ***Unbolt the engine electric ground. Be certain to reconnect this ground. It is the most important connection on the car, we often add a second ground across a motor mount.***

4. Remove flywheel and replace the rear crankshaft seal. It will never be easier to reach. Install a new pilot bearing, if you don't it will fail later .Use the new sealed bearing type and get rid of the old felt and tin plate pieces.

Now that you have your beautiful machine in a million pieces, most of which you never thought you would see out of the vehicle, take a good rest. Let your nerves recover. It will be a BMW again. If you think you might be in over your head, you might want to have a consultant around. The assembly should go fairly smoothly, but I would allow plenty of time as you will probably need a key part that will have to be ordered.

5. Reinstall manual transmission type flywheel and clutch (we use Alpina B7 type it's cheap).

6. Install late style bell housing, throw out bearing, throw out fork and pivot (Plus retainers).

7. Bolt up the five speed (uses the same hardware as the four speed). We renew the rear trans seals at this time.

8. Install five speed shift assembly, gearboxes cross member (this just straddles the large openings on the bolt track) and drive shaft. To support the rear of the five-speed shift platform use an airflow meter mount (all holes are present). We use a blend of Redline MTL and 80/90 mineral oil (50:50 part for easy shifting and part for noise reduction).

9. Install five-speed drive shaft

10. Replace exhaust system. The exhaust hanger from a 2800 auto gearboxes fits best to support the exhaust at the rear of the transmission.

If this sounds simple it is. The real trick to the installation is in knowing the various pieces that need to be combined to fit the five speed simply and easily into the CS.

The following is a list of the parts required to install a five speed overdrive gearboxes into a CS. In simple words we are trying to install the 528i five-speed transmission into the CS. The dimensions of the 528i tunnel are the same as the Coupe. If a gearboxes assembly from a 6 or 7 series is used the shifter components will need to be exchanged for a 528i. All of the bolts, mounts, etc. are the same. It's a bolt in. The problems occur because of a change in 1974 to the bell housing and throw out bearing components. The bell housing is different, and must be used with the five speed (trust me on this one). The clutch slave cylinder is of the new style for this bell housing, ditto hydraulic hose, throw out bearing, fork, and pivot. The five speed gearboxes cross member is needed to clear the gearboxes, and the shorter five speed shifter pieces are needed for the shift knob to pop up through the opening in the tunnel (again the 528i). Add the corrected length five speed drive shaft and we are shifting. The 528i has a mounting bracket in the tunnel to support the rear of the shift platform. By using an airflow meter mount, it is possible to pick up the rear of the shift platform and hang it from the tunnel using the rear auto shifter mount point. The speedometer cable for the automatic is the correct length for the five-speed conversion.

A few special notes for those going from automatic to manual. You will need a flywheel and new securing bolts (long 28mm type) [same as Bavaria]. Pressure plate retaining bolts 8mmX20mm. The bolts that secure the auto to the engine are different from those that attach the manual bell housing. You must get this hardware early. The bolts are unusual lengths, as always special order. The manual radiator is different (there is no cooling tank on the right), as is the right hand bracket, you can retain your auto radiator if you like. The shifter surround will have to be modified. If you turn the platform over the opening for the manual is partially cut. Peel the vinyl back, complete the opening, build up the leading edge of the platform, under the vinyl, to flush, pull the vinyl back into position and glue. Install zippered shift boot with tacks or staples. It will be necessary to remove the starter interrupt relay. Follow the black wire down from the back of the ignition switch. It will go into a relay. Unplug the black wire and plug it into the clear connector under the fuse box with a similar black wire. This will be occupied with a black and white wire from the same relay. Remove the relay and extra wires.

You should also remove all of the wires for the shift indicator and the lamp assembly. A jumper will have to be made up for the reverse lamps. Two wires from the switch on the transmission to the connector in the passenger compartment at the firewall below and to the left of the steering column. This connector has three wires gray/red, blue/white and violet/black. Use the last two. You will need to change out the pedals. This is a simple bolt in. Use a pair of pedals from a Bavaria. They go right in. Be certain to install the return springs. ** 1974 and later clutch pedal has a top bracket that will not fit into the early pedal box. The early pedals will fit all pedal boxes. Do not try to use 528i pedals, the bushing split does not line up (trust me again).** You will need to install a clutch master and the special bolt to attach it to the clutch pedal (also 2 nylon bushes). The holes are in the body (the shift indicator wires feed through this opening).*** The really bad news is that the clutch master cylinder is now extinct. We are trying to get another production run.*** A used unit may have to be reconditioned. Next install the hose to the slave. The brake fluid reservoir will have to be changed out for the manual type with clutch feed hose.

Install with feed hose. Bleed clutch.

PARTS LIST

Late bell housing Throw out bearing Throw out fork Fork pivot Fork retainer spring Clutch kit, with pilot and rear main seal Late clutch slave cylinder and 8mm nuts (2) Extension hose for slave 5-speed transmission 5 cross member Gearboxes mount Auto speedometer cable 5 shift platform Shift platform mounts (2) 5 shill rodE21 3 series lower shift lever Shift lever bushings Retainer clips Shift joint Foam pad Shill shaft seal Gearboxes output seal Hardy disc Center support bearingAFM mount and 6mm hardware

Purchase used unit21-51-121-51-1-204-22921- 52-121-52-1Purchase used unit23-71-1-175-31423-71-1-245-55225-11-1-205-38625-11-1-220-53925-11-1-220-21323-41-1-666-13325-11-1-220-37925-11-1-220-19823-41-1-200-93626-11-126-11-113-62-1-359-216

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-----Original Message-----
From: Dale & Sheila Olson
Sent: Tuesday, March 19, 2002 9:34 PM
To: SSR list; CS Registry
Subject: made some progress on the bav

The saga continues...

In order to get the transmission out, I needed to get the shifter out of the tower. To do that, I had to get the allen set screw out of the bottom of the shift lever that holds in the pin in the plastic bushings and rod to the transmission. After totally trashing one allen wrench without affecting the screw, the application of heat was considered.

First I removed all the stuff on the top of the shift lever, the chrome lever, rubber bushing, washer and snap ring. (knob and boot already off) Then I got out the foam pad from between the shift tower and the bottom of the transmission tunnel by pulling it up through the hole in the tunnel. I could do this because I had taken out the bottom two mounting bolts on the tower and it had dropped down a little. Using the smallest tip on the Ox/acet. torch, I heated up the screw to cherry red. It backed right out. Then I tried to move the pin. Yea right. It was stuck but good. After switching to a bigger tip I started heating the shift lever. That's when things got interesting with the plastic bushings, as they melted, ignited and dripped down on me. I was able to extract the pin,but not until all the plastic was burning. A quick douse of water from the bucket (always on hand when I use the torch) and a open garage door for a couple minutes to clear out the (probably toxic) smoke took care of the after effects.

After the four trannie bolts, it was pretty straight forward to pull the transmission back and let it down on the floor. I see now why the new style bellhousing and clutch throwout arm has to be used with the 5 spd. the pivot point for the 4 spd. throwout arm actually is fastened to the front of the 4 spd. transmission, and pokes through a hole into the bellhousing. No such pivot on the 5 spd. I was sweating it a little bit when I couldn't get the speedometer drive gear and piece with the rubber o-ring out of the 4 spd., but after switching to a pair of bigger screwdrivers to pry with, I managed to break it loose, pull it out, clean it up and get it installed in the 5 spd. It's nice to know I'll have a speedometer when this is all done.

I got a hold of a BMW recycling yard and have a 5 spd. shift tower and transmission crossmember on it's way, two of the pieces I'll need to finish this project at some point in the barely foreseeable future.

Next on the agenda: hooking up the cherry picker to the motor and pulling the bellhousing, clutch and flywheel. Then dropping the crossmember so I can drop the oil pan and crank for the new bearings. I'm going to try this without removing the engine from it's location in the body as I don't need to do any top end work. Don't know if this is smart or not, but at this point it makes sense to me. As the project progresses, it might just end out coming all the way out anyway.

Dale O.

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-----Original Message-----
From: Ben Thongsai
Sent: Saturday, January 15, 2000 1:09 AM
To: Orp1of5@aol.com
Subject: Re: 5 spd conversions vs total transplant

On Fri, 14 Jan 2000 Orp1of5@aol.com wrote:

So, what's the best way to proceed with the transmission conversion project? Options:

I know the recommended option is the '81 528i getrag because they're equipped with the mechanical speedo cable, but they're rare, (possibly because they're already residing in your cars...)

I've been told that an '85 transmission can also work (supports a motronic engine, but it's said to have a mechanical speedo connection that can be tapped out)

'85s use the old Getrag 265 trans, which has a provision for a mechanical speedo drive. The E30 M3 ('88-'91) also uses this transmission with the correct bellhousing and will bolt right in a coupe. You can find these floating around for reasonable money. Either way, you'll need the shifter assembly from the 528i or '85 535i. You'll also need the 528i trans mount crossmember and mount. (the one from the '85 535i is much nicer, but happens to line up with the cutouts on the mounting tracks on the floor of the car. Might sound confusing, but you'll figure it out quickly when you try it in real life.)

What happens if I put some other motronic 5-speed in? Do I lose the ability to hook up the tach?

The tach is not affected with any transmission swap. Only the Getrag 265 has a provision for the mechanical speedometer drive. The other 5 speeds (mostly Getrag 260) do not have any provision for a speedo drive. The cars that use this trans have electronic speedos that pick up a signal from the differential.

Finally, is it possible/recommended to swap out the entire drive train to a motronic 3.5 liter injected 5 speed all the way back to & including the rear end (where I think the tach connects)? Even if it can connect, how does one convert from electronic equipment to mechanical tach/odometer in the dash.

A motronic 3.5 conversion is nice from a performance/driveability standpoint, but is not worth doing if all you want is a 5 speed. Don't even think about installing a newer style differential, the mountings are nothing alike. You'll run into incredible levels of difficulty.

Ben