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winstontj

Differences between various 5-spd OD (Getrag 245) gearboxes?

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EDITED to add 3-bolt / 4-bolt output flange details:

 

I've got three 5-spd OD boxes with M10 front housings (from e21 320is cars). I have no idea what year e21 the boxes came from. The input shaft ?? (part that goes into the PP & clutch) is shorter on two of the boxes and longer on one. The only thing I can confirm is that the box with the longer input shaft ?? (pp & clutch side) is a 3-bolt output flange. I've got a ton of driveshafts and can't tell what is what as they are all up in the rafters so I can only guess on length and what goes to what car. I think that the two gearboxes with the shorter input shaft (pp & clutch side) **might** be 4-bolt output flange gearboxes but not sure. 

 

What is the difference between a gearbox with a short vs. long input shaft (pp & clutch side)? Does it make any difference in terms of clutch, pp, pilot bearing or flywheel?

 

I was moving the gearboxes around to make room for the motor & drivetrain from the '71 and noticed the differences randomly. Two are about 1/4"-1/2" recessed from the bell housing plane and the input shaft (PP & clutch side) on the 3-bolt flange gearbox protrudes (stick out past) the bell housing plane about 1/4"-1/2". 

 

The gearboxes are wrapped up and sealed and I don't really want to open them so I can't provide exact casting dates or numbers. The only reason why I know that the one box is a 3-bolt flange is AceAndrew's post (#2) reminded me to check the driveshaft. Other than that I only know they are 5 speed OD boxes out of US model e21 320is cars. IIRC there may have been two types of 5-speeds but I see RealOEM lists a 245/4 for every year from 1976 up through 11/1982. 

 

I also know that the gearbox with the longer front input shaft ?? (pp & clutch side) was the one that I had in my '74 at one time which makes me wonder if the other two are just slightly different or could they possibly be damaged?? 

 

Thanks. 

Edited by winstontj

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As you note there is roughly a half inch difference between the 4-bolt and 3-bolt output flanges.  This does effect driveshaft length (you'll have to swap it out if you want to swap the trans out to one with a different flange).

The input flange (pp and clutch side) can take a couple different shapes (and bolt patterns) but they don't effect overall length, at least not that I'm aware of.  Other than that there were a couple internal differences regarding bearings.  I've seen a M20 housing that wasn't threaded for the back-up light switch oddly. 

 

I believe the change in flanges happened around the 09/1979 mark (later cars getting the 3-bolt flanges).

Edited by AceAndrew

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I think I was wrong when I said "output shaft" however you may have given me what I need with the 3-bolt vs. 4-bolt output flanges.

 

I meant what you are referring to as the input flange/shaft (pp & clutch side) length. I'll edit my post to reflect that. Two boxes have a flush or slightly recessed input flange/shaft (PP&Clutch side) and one has an input flange/shaft that sticks out about 1/4"-1/2" from the bell housing plane. I'm wondering only because I'd think they would take different pilot bearings, at least. 

 

Are the bearings in one any stronger/better than the other?

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I've never looked at that.

 

And I've never had a 5- speed not stab into the clutch just fine.

 

Can you tell if the shoulder where the shaft gets bigger after the pilotting surface is also moved 'forward' or out of the bell?

 

I suppose one possibility is that one of yours is messed up internally, but that seems unlikely.

 

t

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And I've never had a 5- speed not stab into the clutch just fine.

 

Spoken like a true gentleman... 

 

Just measured (by shoving my hand into the bell housing and feeling around). It appears/feels like the needles (the stabbing into the clutch end/part) are both the same length. It also appears that the splined section on the 3-bolt box is slightly LONGER than the splined section of the 4-bolt boxes. 

 

Once I get the nose panel off the car I'll climb back under the bench and measure with something other than my hand. 

 

I'm mostly concerned with whichever gearboxes have the most robust gears, bearings & syncro's. Also if they are all interchangeable, given they all have the same 3-bolt flanges on them. 

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They only made that box for 3 years-  I've interchanged them (including moving the flanges around) with

no problems.  But it's Getrag- I suspect if we took apart 10 boxes, we'd find 3 variants, at least.

 

That said, I'll bet you it doesn't matter- they're all 'type compatible' for the M10.  But I'm only betting you a pop- tart,

because BMW's a very low- volume car manufacturer in 1982-3...and did all sorts of odd stuff.

 

hee

 

t

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The general opinion of folks on the Board over the years is that the earlier 5 speeds with three piece cases are more robust than the later ones with the two piece cases.  

 

The early boxes were basically the four speed housing with a 90mm section interposed between the main housing and the rear housing.  That 90mm is where the fifth gear lives, and is what requires shortening the 2002 drive shaft to fit.  Later gearboxes have a completely new housing in one piece that's the same overall length as the earlier boxes.

 

mike

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(edited)
 

The general opinion of folks on the Board over the years is that the earlier 5 speeds with three piece cases are more robust than the later ones with the two piece cases.  

 

 

 

Mike, we are talking about the nuances/differences of the 245, not really covering the 240 at all here.

 

 

Winston, there's a couple pictures at the bottom here went I learned the inner workings of the 245 from Rob.  There should be a picture highlighting at least the differing main shaft bearing (the others would be slightly different as well.  Syncros are all the same though.)

 

http://www.bmw2002faq.com/topic/116731-m20-triple-weber-build-x2/page-6

Edited by AceAndrew

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