Are there two lengths of 5spd M10 geearbox?

For all your questions, problems and DIY stories
Reck
E21 Pro
Posts: 779
Joined: Mon Mar 29, 2010 12:26 am
My E21(s): 83 316, 1.8 M10, RHD
Location: Manchester, UK

Are there two lengths of 5spd M10 geearbox?

Post by Reck »

As above. Me and Nas swapped out M10's last week. Took the opportunity to change the old 5 speed for a rebuilt unit at the same time - except it wouldn't fit, the prop was too long. Was anyone aware that there are two lengths of 5 speed box for the M10? I thought all 5 spds were the same dimensions..


User avatar
e21-Mark
E21 Master
Posts: 5716
Joined: Fri Mar 21, 2008 2:19 pm
My E21(s): 316 m52/2.8 Cat Cams & Jenvey ITB
Facebook page: https://www.facebook.com/JackyardBackoff
Location: Cornwall - UK

Re: Are there two lengths of 5spd M10 geearbox?

Post by e21-Mark »

You should find part number info etc here.

Are you sure both boxes are 5 speed? There is a difference in length between 4 and 5 speed boxes. I'm pretty certain reverse is always top left on all m10 boxes?

The 320i has undergone numerous changes since the 1977 model was introduced to the U.S. market in 1976. A true BMW aficionado can identify the many differences by year, such as which year had ventilated front disc brakes or which years had the "S" package available in polaris silver.
The most significant changes to the 320i came in 1980 with the introduction of a smaller displacement engine. This was due largely to stricter exhaust-emission requirements, concern for greater fuel economy and CAFE standards. As a result, fuel economy was increased by 30 per cent. This achievement was accompanied by other modifications, including reduced vehicle weight, a revised emission-control system and an overdrive 5-speed transmission.
A 5-speed gearbox, overdrive or otherwise, was unavailable as an option for the '77-'79 320i. However, the '80-'83 model, equipped with an overdrive 5-speed as standard equipment, became a ready source for retrofitting the earlier models. Two overdrive 5-speeds are available through the BMW remanufactured parts program. One is for the '80-'82 models, part No. 23 00 1 209 775, and the other is for the '83 year only, part No. 23 00 11 220 421.
An overdrive 5-speed is a welcome addition to the older 3-series for various reasons. First, in topgear the engine RPMs at a given speed are reduced. The engine would not have to work as hard, thus, reducing wear.
Second, highway fuel economy is increased, though it would be difficult to justify the conversion cost on fuel savings alone.
Finally, and perhaps the best justification for the conversion, is the increase in highway driving pleasure. An overdrive fifth gear would not only reduce engine RPMs, but would also reduce the accompanying engine noise or "buzziness" characteristic of four-cylinder BMWs at highway speeds.
Although the scope of this article is directed to the installation of an overdrive 5-speed, installation of a close-ratio 5-speed is essentially the same since both gear-boxes have identical dimensions.
Those active in competitive events should consider the close-ratio 5-speed. For a discussion of close gear ratios or installation of a 5-speed in a 2002, see Jeff Mulcahey's article in the September 1982 Roundel.

The '77 320i is equipped with the Getrag 242/94-speed with gear ratios of 3.76/2.02/1.32/1.00.
The 4-speed in the '78 and '79 3-series is fitted with an additional backup light switch for "ignition switching" and is designated the Getrag 242/18. The switch controls a vacuum valve in top-gear that is disconnected in the conversion. Interestingly, the switch is responsible for the audible "pop" from the radio speakers when shifting from fourth gear to neutral. The Getrag 242/18 and 242/9 have identical gear ratios.
The '80-'83 320i, nee 318i, is equipped with the Getrag 245/4 overdrive 5-speed with gear ratios of 3.68/2.00/1.33/1.00/0.81. It is noteworthy for comparison that the fourth gear ratio is the same for all 3-series.
The '80-'83 320i also has a lower final drive gear ratio of 3.91 as compared to the older models' 3.64. The 3.91 differential is neither necessary nor recommended for the conversion and with the two-liter engine is best suited for competitive driving.
The 5-speed is 87mm longer than the 4-speed. Both transmissions utilize the same housing, the difference being that the 5-speed has an additional section added between the front casing and rear cover to accommodate the overdrive gearing.
Installing the 5-speed in a '77-'79 320i requires that three components be shortened: the selector rod (shift linkage), shift arm (linkage holder or shift tower) and propeller shaft (driveshaft). Installation also requires a longer speedometer cable.
All parts necessary for the conversion are readily available from BMW NA. They are:
Selector rod 25 11 1 206 888
Shift arm 25 11 1 208 464
Propeller shaft (see text)
Speedometer cable 62 12 1 359 333
The existing shift arm can easily be shortened; it is predrilled to accept a 5-speed. Simply use a hacksaw to remove 90mm of the forward portion. Protect the exposed metal with Rust-oleum or other rust-preventative paint.

The selector rod can similarly be shortened but welding is required. Use a hacksaw to remove 90mm from the center of the selector rod. Weld the remaining pieces after checking their alignment. The purchase of a shorter selector rod would prove more convenient to those without welding equipment.
The propeller shaft is the most difficult component to shorten. If the 5-speed gearbox is purchased used, the propeller shaft should ideally be negotiated in the transaction. Otherwise there are two options. Either purchase the shorter propeller shaft or have the original one shortened 90mm and balanced by a competent shop.
Purchasing a new propeller shaft for the conversion is not as easy as it sounds. There are three available, part Nos. 26 11 1 208 540, 26 11 1208 608 and 26 11 1 225 477 for years '80, '81-'82 and '83, respectively. Their differences are not indicated on the BMW parts microfiche but relate to the different flange bolt patterns. Suffice it to say that if the propeller shaft is purchased new, caution should be exercised to see that the proper one is ordered to match the gear-box output flange.
The early 5-speeds have the same four-bolt output flange as the 4-speeds. The late 5-speeds have a three-bolt output flange. The proper propeller shafts have corresponding flanges.
Also, there are two types of Giubo couplings. The eight-bolt Giubo, which is the same as in the '77-'79 3-series, is used with the four-bolt output flange, is slightly thinner and takes shorter bolts.
The only potential problem in coordinating propeller shafts occurs when a late 5-speed with a three-bolt output flange is to be installed with a shortened four-bolt propeller shaft. This is easily overcome by replacing the output flange with a four-bolt output flange, part No. 23 21 1 208 536.
Final preparations include replacing the gear oil and installing a new backup light switch. On '78-'79 models the backup light switch wire must be lengthened. These are easy tasks while the transmission is out of the car. The front and rear radial oil seals should be inspected and replaced if necessary.

Unlike the 2002 5-speed conversion, the 320i conversion is a bolt-in operation.
The actual installation process is very straightforward. The original fasteners and cross member are used. The lower speedometer cable, though, is replaced with a longer one.
Unlike the 2002 5-speed conversion, the 320i conversion is a bolt-in operation. This is made possible by a cross member that adjusts fore and aft on sliding tracks. The cross member is the 2002, by contrast, is mounted on brackets that must be removed and repositioned for the conversion.
The final product of the conversion is a two-liter 320i that is a sheer pleasure to drive at highway speeds. Engine RPMs in topgear are approximately 20 per cent lower than in fourth gear. Following are the overdrive reductions in engine RPMs at selected speeds: at 60 mph, from 3,000 to 2,400; at 70 mph, from 3,500 to 2,800; at 80 mph, from 4,100 to 3,300; and at 90 mph, from 4,600 to 3,700.
Engine noise or whine is decreased significantly to surprisingly low levels. This is a major benefit that should not be underestimated.
The overdrive 5-speed is responsible for a 17 per cent increase in highway fuel economy, from 22.3 MPG to 26.0 MPG. The U.S. Environmental Protection Agency estimates annual fuel costs for new vehicles with a formula of 15,000 miles of driving per year with fuel at $1.25 per gallon. Under this method, the annual fuel cost for a vehicle obtaining 22.3 MPG is $840. The yearly fuel cost for an automobile capable of 26.0 MPG is $722. The conversion would theoretically yield a $118 savings in annual fuel cost.
An added benefit of the conversion is the increase in cruising range. Cruising range is extended from approximately 300 miles to 350 miles per tank of gasoline.
The overdrive 5-speed conversoin is recommended for those who enjoy spirited highway driving. While the savings in annual fuel cost and reduced engine wear are long-term benefits, the increase in highway driving pleasure is immediate.
Reck
E21 Pro
Posts: 779
Joined: Mon Mar 29, 2010 12:26 am
My E21(s): 83 316, 1.8 M10, RHD
Location: Manchester, UK

Re: Are there two lengths of 5spd M10 geearbox?

Post by Reck »

Saw that on google but it seems to suggest 5spds are the same dimensions.

Both boxes are definitely 5 speed as I've driven them both! One in my current 316, and the rebuilt one in my old 316. We also had that 4spd out of your beige 316 lieing around and that was significantly smaller and lighter than both 5 speed boxes.
User avatar
e21-Mark
E21 Master
Posts: 5716
Joined: Fri Mar 21, 2008 2:19 pm
My E21(s): 316 m52/2.8 Cat Cams & Jenvey ITB
Facebook page: https://www.facebook.com/JackyardBackoff
Location: Cornwall - UK

Re: Are there two lengths of 5spd M10 geearbox?

Post by e21-Mark »

I assume you haven't got both props then?

Do they both have the same number of bolts on the output flange? (3 or 4 bolt)
User avatar
e21-Mark
E21 Master
Posts: 5716
Joined: Fri Mar 21, 2008 2:19 pm
My E21(s): 316 m52/2.8 Cat Cams & Jenvey ITB
Facebook page: https://www.facebook.com/JackyardBackoff
Location: Cornwall - UK

Re: Are there two lengths of 5spd M10 geearbox?

Post by e21-Mark »

Is reverse in different place on each?
Reck
E21 Pro
Posts: 779
Joined: Mon Mar 29, 2010 12:26 am
My E21(s): 83 316, 1.8 M10, RHD
Location: Manchester, UK

Re: Are there two lengths of 5spd M10 geearbox?

Post by Reck »

Yep, I do have a prop that was shortened and balanced for the refurbed 5 speed - but I didn't take it to Leeds as I (wrongly) assumed all 5 speeds were the same size. Taking it up tomorrow. Nas should be able to confirm on the output flange but I believe they were the same. It's only been a week since I've driven it and I'm struggling to remember where reverse is. 99% certain top left on both.
Last edited by Reck on Fri Jan 18, 2013 4:55 pm, edited 1 time in total.
User avatar
e21-Mark
E21 Master
Posts: 5716
Joined: Fri Mar 21, 2008 2:19 pm
My E21(s): 316 m52/2.8 Cat Cams & Jenvey ITB
Facebook page: https://www.facebook.com/JackyardBackoff
Location: Cornwall - UK

Re: Are there two lengths of 5spd M10 geearbox?

Post by e21-Mark »

Can you take some pictures of boxes?

All I can think is that it's an Opel 5 speed? All BMW have reverse in same position too so are both these boxes the same gear pattern?
Reck
E21 Pro
Posts: 779
Joined: Mon Mar 29, 2010 12:26 am
My E21(s): 83 316, 1.8 M10, RHD
Location: Manchester, UK

Re: Are there two lengths of 5spd M10 geearbox?

Post by Reck »

The refubed one is in car now so won't be able to get pics unfortunately. Just edited as you replied, yes gear pattern is same. Fingers crossed this shortened prop fits.
User avatar
mr edd
E21 Fanatic
Posts: 236
Joined: Thu May 31, 2007 12:32 am
Location: wigan! england

Re: Are there two lengths of 5spd M10 geearbox?

Post by mr edd »

some very late e21's had a getrag 240 5 speed which is smaller than the getrag 245 most m10 5 speeders had ....the getrag 240 is not much bigger than a getrag 242 4 speed ...
e21 320 (12/1975) 320i/4 (3/77)running gear.
e36 318is coupe (1996)
e21 316 (1981)
Reck
E21 Pro
Posts: 779
Joined: Mon Mar 29, 2010 12:26 am
My E21(s): 83 316, 1.8 M10, RHD
Location: Manchester, UK

Re: Are there two lengths of 5spd M10 geearbox?

Post by Reck »

A-ha you may well have cracked it there Edd. My current 316 is a mid 1983, so very late in production. I guess the longer 5 speed we've installed is the Getrag 245 and the shorter one we took off is the 240. Looking around online the 245 is meant to be significantly tougher, so that makes me happy that we took the time to swap. :-)
User avatar
e21-Mark
E21 Master
Posts: 5716
Joined: Fri Mar 21, 2008 2:19 pm
My E21(s): 316 m52/2.8 Cat Cams & Jenvey ITB
Facebook page: https://www.facebook.com/JackyardBackoff
Location: Cornwall - UK

Re: Are there two lengths of 5spd M10 geearbox?

Post by e21-Mark »

If it is a 240, that's the same box as used in Opel Manta etc. Either way, once you install the correct prop you should be fine.

Give me the nod if you want to flog your old box please? I could drop it in my 02.
drjim
E21 VIP
E21 VIP
Posts: 1084
Joined: Fri Nov 03, 2006 11:32 pm
Location: Manchester Uk

Re: Are there two lengths of 5spd M10 geearbox?

Post by drjim »

What engine have you swapped in???
1983 316 Pustergrun - track sluG!
1982 Saphirblau Baur 325i

Cars all gone!
User avatar
nas80
E21 Mad
Posts: 2975
Joined: Sun Jun 14, 2009 12:12 am
Location: West Yorkshire

Re: Are there two lengths of 5spd M10 geearbox?

Post by nas80 »

Another m10
[img]http://s13.photobucket.com/albums/a285/nasbucket/forumsig.jpg[/img]
drjim
E21 VIP
E21 VIP
Posts: 1084
Joined: Fri Nov 03, 2006 11:32 pm
Location: Manchester Uk

Re: Are there two lengths of 5spd M10 geearbox?

Post by drjim »

Figured that, but I thought this car had a good engine in it. Where's the new one from, rebuilt or fingers crossed it's OK??

Went a bit better than the swap on the other car even though it still isn't mobile. Think the other car sat in my unit for 2 months!
1983 316 Pustergrun - track sluG!
1982 Saphirblau Baur 325i

Cars all gone!
User avatar
nas80
E21 Mad
Posts: 2975
Joined: Sun Jun 14, 2009 12:12 am
Location: West Yorkshire

Re: Are there two lengths of 5spd M10 geearbox?

Post by nas80 »

Lol yea and there was no idiot driving a fork lift through a metal shutter door this time!

Reck is on his way here now... we are changing this prop in the snow. :(
[img]http://s13.photobucket.com/albums/a285/nasbucket/forumsig.jpg[/img]
Post Reply