engine and drivetrain Transmission Questions

[1972-2002]

i took the engine and tranny out of my 02 the other day. now I would like to do two things

 

1. date the tranny. my car is an 1972 but the engine is a 74 should i assume the tranny is a 74 also or is there a way to date the tranny. i assume it is a 74 also but want to make sure.

 

2. Any recomendation on somewhere to take the tranny to have it looked over and rebuilt in the SF bay area. Should i just take it to any tranny shop or do i need to take it to a BMW specialist?

 

Thanks for your help as always

 

Garry

[FunkyLaneO]

Look for a casting date on the case somewhere, though it doesn't really matter, 72 and 74 used the same transmission, the very early ones had different syncros and a different spline on the output shaft.  If there is nothing wrong with your transmission then I wouldn't bother having it worked on, the parts are very expensive and 4 speed boxes in good condition are a dime a dozen used (well more like $50-$75)  If it shifts well I would just replace the seals, change the fluid and put it back in.

[jgerock]

Look inside the upper bellhousing for a date stamp.  This is only for the transmission casing.

Edited September 26, 2013 by jgerock

[M3M3M3]

Look for a casting date on the case somewhere, though it doesn't really matter, 72 and 74 used the same transmission, the very early ones had different syncros and a different spline on the output shaft.  If there is nothing wrong with your transmission then I wouldn't bother having it worked on, the parts are very expensive and 4 speed boxes in good condition are a dime a dozen used (well more like $50-$75)  If it shifts well I would just replace the seals, change the fluid and put it back in.

+1

if it works, don't fix it.

[1972-2002]

got it. it seemed to work well so i won't rebuild it.

 

What seals should i replace. Ok i am a rookie at this. part number or names would really help. or a kit from someone like ireland.

 

Garry

[FunkyLaneO]

Best bet would be to contact Steve at Blunttech and tell him what you have and he will know what you need.

 

What I normally replace is:

output shaft seal and housing gasket (as I recall there are 2 different sizes for this one so you need to measure your old one)

input main shaft seal

and maybe the selector shaft seal (i have only needed to replace these on 5 speeds so yours may not need it)

 

But if your transmission is not leaking then you may not need to replace anything, those seals last a long time, I just usually replace them for good measure since they are cheap.

[ray_]

+1

if it works, don't fix it.

 

 

HAHAHAHAHA!

 

Have you seen this site? http://www.bmw2002faq.com/topic/103584-mlytles-m2-madness/

 

Cheers,

 

Ray

[jgerock]

I'm in the middle of changing out the seals in my 4-speed that came in the 69.  I just look up the seals and gaskets on RealOEM or Penskeparts.com then place an order with BLUNT.   Package should arrive tomorrow .

 

 

[Mike Self]

FYI on 72-73-74 trannys:  they all have the Borg-Warner style synchros, which are nochier feeling than the earlier gearboxes that use a Porsche-style synchro set but last longer.  If your gearbox still shifts into and out of 2nd with no grinding, and there's no bearing whine, then I'd leave it alone.   

 

However...these trannys have two other things to consider:  the idler shaft bearings are ball bearings; they get a side load and will eventually start to fail and get noisy; later gearboxes used a tapered roller bearing that lasts essentially forever so long as you keep oil in the gearbox.  Also, at least some of the 73 gearboxes had poorly heat treated output flanges (the thing on the tranny's tailshaft that the guibo bolts to), and they have coarse splines on the shaft.  The splines on the flange wear and eventually wear off, usually damaging the output shaft itself.  Both of these things happened to the original 4 speed in my Dec '72 production 1973 car.

 

While your gearbox is out, make sure the nut that holds the flange to its shaft is good and tight--and since you'll probably be replacing the output shaft seal (requires removing the flange) you can check both flange and shaft for wear if the splines are coarse.  The later gearboxes (made after January 1974) have fine splines, and they don't have the wear problem of the earlier coarse splines.  Check yours.

 

cheers

mike