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Gearbox & driveline

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Gearbox & driveline

Postby Jeroen » Wed Dec 22, 2010 8:12 pm

Gearbox
Nearly all E21's had the 4-speed manual gearbox fitted. 5-speed boxes are a sought after item for conversion. If you buy a 5-speed try to get it with the matching propshaft (shorter than with 4 sp boxes) and gear shifter meachanism (also shorter). Not all gearboxes fit, E30 boxes lack the built in speedo drive and converting your speedo is not that easy. Better stay away from that. There are both dogleg close ratio 5 speed boxes with a prise direct 1:1 final drive as well as the more common overdrive fivespeed. All gearboxes manufactured by Getrag and M20 6 cil boxes show an M60 sign on the side of the housing.

All E21's were also available as automatic using a ZF 3HP-22 3-speed auto gearbox.

Gearboxes usually last a long time, if you experience clutch judder this might indicate clutch plate is getting thinner. Annoying but usually no need for immediate replacement. Clutch judder is a common issue, especially when the clutch warms up like in a traffic jam, and probably you will mainly experience this when operating the clutch so with clutch slipping, meaning once you let go of the pedal it's ok. Then really the clutch plate is the cause. In some cases it is possible that worn parts in the driveline may worsen the effect, like gearbox mount bushing, propshaft bearing, propshaft centering sleeve, flex disc (guibo) or the diff hanger rubber. A little more remote but also a possible option for wear are the large rear beam bushes at either far end.

Clutch system is hydraulic. Doesn't need adjusting but the system can leak. Info on fixes at the bottom of this page.

Some hints for preventing clutch judder:

NEVER ...
NEVER pull away from a standstill in second gear
NEVER hold the car on a hill with the clutch
NEVER let your foot rest on the clutch pedal when the car is moving, even the slightest touch can cause the clutch to slip
ALWAYS ...
ALWAYS slip the clutch as little as possible when pulling away
ALWAYS select neutral and bring up the clutch pedal if you're stationary for more than a few seconds


Interesting reading:
overview of all gearboxes
5-speed 6 cil M20 boxes compared


Driveline
There aren't too many general driveline issues. Common wear problems are a torn rubber gearbox crossmember support and a worn propshaft center bearing. Both might cause vibrations while driving or accelerating. As with most parts from BMW, replacement parts are available.

All available diff (final drive) ratios can be found on the specs pages. For an interesting topic on establishing if you have a regular open or a limited slip differential (lsd) the following topic is very useful. It also explains how to establish your diff ratio: viewtopic.php?f=3&t=15293&p=154898

Topics:
Replacing clutch plate
Identifying a Limited Slip Diff or LSD


Oils
Manual gearboxes:
Standard: SAE80, 75W90, 80W90
Uprated: Castrol Syntrans B 75 W
Automatic gearboxes:
ATF D2 system Dexron

Diffs:
Standard: SAE90
Uprated: Castrol Syntrax 75W-90
Limited Slip Diff REQUIRES special oil! Recommended: Castrol Syntrax Limited Slip 75W-140 (formerly known as SAF-XJ)
Regards/groeten, Jeroen

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Re: Gearbox & driveline

Postby Reck » Thu Sep 06, 2012 8:48 pm

Great topics in here btw. I'm just wondering. Can anyone explain why you shouldn't do these things? ;

ALWAYS slip the clutch as little as possible when pulling away
ALWAYS select neutral and bring up the clutch pedal if you're stationary for more than a few seconds
ALWAYS use the brakes to slow down the car, not downward gear changes

Of course it says to prevent clutch judder, but I do some of these things - especially slowing down with gear changes to a stop..

And this may be a stupid question, but is there any harm skipping gear on a downshift? I'll often go from 4th to 2nd on a corner (I'm careful with the revs tho)..
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Re: Gearbox & driveline

Postby Danny043 » Thu Sep 06, 2012 9:11 pm

I'm not a walking encyclopedia like some people here, but let me try :smoke

ALWAYS slip the clutch as little as possible when pulling away

To cause as little wear as possible.


ALWAYS select neutral and bring up the clutch pedal if you're stationary for more than a few seconds

So you don't keep unnecessary pressure on the master / slave cylinder?


ALWAYS use the brakes to slow down the car, not downward gear changes

Brake pads are cheap and easy to replace. Replacing internal engine parts, or synchro mesh rings in your gearbox isn't so cheap. It saves fuel when braking in higher gear. Plus having the driveline power the engine causes a lot of stress on internal engine parts.


When you first shift down from 4th to 3rd, and then from 3rd to 2nd, the transitions are smoother. When you skip a gear shifting down, i believe there's a bigger difference in rotation speed of the clutch plate and the flywheel then when you don't skip a gear. Double clutching can help here.
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Re: Gearbox & driveline

Postby Jeroen » Thu Sep 06, 2012 11:06 pm

All these measures are to prevent the clutch plates from overheating which causes them to warp which causes the judder. No prob skipping a gear these days, our gearboxes are fully synchronized so they can cope.
Regards/groeten, Jeroen

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Re: Gearbox & driveline

Postby Reck » Fri Sep 07, 2012 1:10 pm

Thanks guys, that clarifies it.

Ah, that's a shame about slowing down with the gears. I love the noise downshifts make!
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Re: Gearbox & driveline

Postby TopCat » Fri Sep 07, 2012 10:27 pm

other critical item re slowing down with gears alone is that the gears only affect the rear of the car and on a hot lap that is the lightest laden part of the car hence lock-up /lack of control

the best solution is to heel and toe doubledeclutch before turn in point- so you do it alltogether so to speak

Some cars can trail brake into corners (Herman and Butch cannot- but big red can -the hartge)
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Re: Gearbox & driveline

Postby Jeroen » Sat Sep 08, 2012 12:03 am

Yup, and change down too early, too much revving and slowing down from the rear and the rear will have a mind of its own. Somehow I always had that happen to me at the Belgian Zolder track in the Villeneuve chicane and I was really lucky I never went off big time there!
Regards/groeten, Jeroen

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Re: Gearbox & driveline

Postby E21noob » Sun Aug 17, 2014 1:14 am

After alot of research I thought I would add some details to this thread regarding the M10 E21 five speed transmissions.

Was doing it for myself anyway so figured might as well post up.

Hoping for contributions.

I have been through the first and last production months of all E21s models with M10 engines on realoem.com. 315, 316, 318, 318i, 320 and 320i. According to realoem.com these all came with M10s and optional five speed sport or five speed overdrive transmission.

Annoyingly the drawings of all these boxes (and all the E 30 boxes) are identical so they are difficult to tell apart unless you compare individual parts of the differnt boxes up against eachother.

So bear in mind all of this applies to M10 engines.

The E21 M10 came with the 245 and the 240 five speed transmissions. Both in several incarnations.

245 M10 five speed Sport:
245/2.00 T (part number 23001205711)
245/10.00 BO (part number 23001207146)

Recognised by:
- three piece case
- Mechanical speedo output
- Shift pattern: 1st down left, 5th bottom right, reverse same
- Markings should include "245" (follow by more numbers), six unidentified numbers, and the letters "T", or "BO".
- 87mm longer than the 4 speed (requires shorter drive shaft part number 2611120860)
- Four or three bolt output flange 23211208536 or 23211209612
- 120mm between the two top bolts of the bellhousing, as opposed to 140mm for M20 boxes.
- the two top bolts of the bellhousing are M8 (as opposed to M12 on M20 transmissions)
- reverse light switch up top

245 M10 5 speed Overdrive:
245/4.30-GH (part number 23001209775)
245/5.30 ME (part number 23001220421)
245/4.13-GL (part number 23001209891)

Recognised by:
- three piece case
- Mechanical speedo output
- Shift pattern: as 4 speed, 5th top right
- Markings should include "245" (follow by more numbers), six unidentified numbers, and the letters "GH", "GL", or "ME".
- 87mm longer than the 4 speed (requires shorter drive shaft part number 26111208608 (same as sport))
- Four or three bolt output flange 23211208536 or 23211209612
- 120mm between the two top bolts of the bellhousing, as opposed to 140mm for M20 boxes.
- the two top bolts of the bellhousing are M8 (as opposed to M12 on M20 transmissions)
- reverse light switch up top


240 M10 5 speed overdrive ("late" models)
240/5.30-ME (part number 23001220421)
240/5.31-MF (part number 23001220423)

Recognised by:
- 2 piece aluminium case
- Mechanical speedo output
- Shift pattern: as 4 speed, 5th top right
- Markings should include "240" (follow by more numbers), six unidentified numbers, and the letters "ME", or "MF".
- smaller than the getrag 245, not much bigger than a getrag 242 4 speed.
- three bolt output flange 23211224091
- somewhat longer, requires shorter drive shaft part number 26111225470



Sources:
viewtopic.php?f=3&t=19414&p=200589&hilit=M10+transmission#p200589

http://www.bmwe21.net/?page_id=124

http://www.bmw2002faq.com/topic/131259- ... nsmission/

http://www.bmw2002faq.com/topic/131907- ... etrag-245/

http://www.justanswer.com/bmw/24w66-bmw ... -spec.html

http://e21.tricord.be/e21/about/notes/m10-gearbox.php
Last edited by E21noob on Tue Aug 19, 2014 12:50 pm, edited 4 times in total.
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Re: Gearbox & driveline

Postby Jeroen » Sun Aug 17, 2014 12:06 pm

Great, excellent additional info, thanks for sharing your research!
Regards/groeten, Jeroen

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Re: Gearbox & driveline

Postby E21noob » Sun Aug 17, 2014 7:25 pm

Do you have anything on how to decipher the numbers on boxes and how to determine a partnumber without knowing the car a box came from?
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Re: Gearbox & driveline

Postby Jeroen » Sun Aug 17, 2014 10:57 pm

Problem is that the numbers usually are on the rear covers and it sometimes seems Getrag picked those covers randomly. But the M20 boxes always have M60 on the LHS (the original model designation of the M20 engine).
Regards/groeten, Jeroen

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Re: Gearbox & driveline

Postby Jeroen » Tue Sep 30, 2014 12:39 am

Hydraulic clutch operation & issues
The clutch system on the manual E21's is a hydraulic system running on brake fluid. The system gets its fluid from the same tank as the brake master (for LHD models, RHD have a separate tank). Pick up is about halfway the container so a leak in the clutch system can never lead to brake failure. Leaks usually appear in colder times. The already old seals will decrease in size and fail. Most times you will find your clutch is gone will be on cold winter days.

Master
From the reservoir fluid goes to the master cylinder that is located behind the clutch pedal, but it is hiding behind the under dash cover. Just a few screws removes that cover. The master might leak and spill agressive brake fluid into your floor mat and corrode the bottom of the car, make sure to clean up and dry the mat before putting it back! Newspapers can be a good protective solution as well.

The master can be replaced, but an overhaul kit from the dealer's (P/N 21521 155 030) of from any general friction parts specialist will do the same at a significantly lower price. Undo the pedal connection (bolt) and push the pedal up to make room. Place plastic over your floor and have a container ready. Remove the circlip and pull out the piston, straight towards you. Probably the brake fluid will be gushing out but that will only be a small quantity, max 100cc.

Clean up, make sure not to spill on mats or paint (with your hands too!). A simple Midlock hone tool on your battery drilling machine and some real light honing action makes sure the inside of the cylinder is clean and free of rust. The master is 19mm in diameter, the Midlock CF-64 covers 13-50mm and works well, the larger CF-63 should cover diameters from 19mm on but is too big already. Cost? Abt 10 euros I guess.

Thoroughly clean up the inside of the cylinder with a clean and dry cloth. Place the overhaul kit with a little bit of brake grease (Até or similar) and push the rod in, straight and carefully, without excessive force. The new seals are ruined easily. When fitted you can place the circlip and fit the pedal again.

Slave
There are overhaul kits for slaves as well, but as they usually are pretty cheap I recommend replacing those as a whole, easy job. Undo the line and the two bolts and it comes off. A leaking slave usually is hard to diagnose as the fluid seeps into the gearbox bell housing. But if you have no pressure and there are no outside leaks on the master (and there is enough fluid in the tank and the hoses are good), 99% sure its the slave anyway.

Bleeding
This can be no hassle at all, or a complete pain, so be prepared. After work, top off the container to the max stripe. Make sure the line descends nicely from the tank to the master. Connect a hose to the slave, open the (7mm) bleed nut 1/2 turn and see if you have any fluid at all. In many cases the bleed nipple is clogged up. Easiest is to have one person close the gap on the slave after removing the bleed nipple, while another cleans up the removed nipple. After that you may be able to just pump fluid and bleed with the pedal. A pressure bleeder like Eezibleed on the tank is even easier.

No pressure on the pedal yet? You can try to put pressure the other way around, on the bleed nipple, just beware of leaks and spray at the side of the container, brake fluid will eat your paint! Spilled brake fluid always needs to be removed with excessive water. Sometimes things will be much better already overnight. Usually I manage to get it 75% good already with the Eezibleed, and do that again after 1 or 2 nights, then all the air is pretty much out and your clutch is back to normal.
Regards/groeten, Jeroen

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Re: Gearbox & driveline

Postby Jeroen » Wed Oct 14, 2015 8:36 pm

Useful diff background and build info here!
http://www.bmw2002faq.com/_/technical-a ... -build-r74


limited slip diff sper sperre lsd sperdiff
Regards/groeten, Jeroen

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Re: Gearbox & driveline

Postby Jeroen » Thu Sep 08, 2016 8:27 am

Propshaft specs gathered sofar (lengths!), additional data is most welcome!

4 cylinder models:
4sp 3-lug 163,7 cm
4sp 4 lug ?
OD 5sp 3-lug 155,0 cm
OD 5sp 4-lug ?
Auto 3-lug 150,1 cm
Auto 4-lug ?

6 cylinder models:
OD 5 sp and 5-Sport 3-lug 147.3 cm
OD 5 sp 4-lug ?
4sp 4-lug 154.7 cm
4sp 3-lug ?
5-sport 4-lug 149.9 cm
Auto 3-lug 142.3 cm
Auto 4-lug ?
Regards/groeten, Jeroen

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