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232 Bell with 242 Drive Shaft


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Anyone know if it is possible to use a 242 Drive shaft with a 232 Bellhousing?  My 232 Drive shaft is junked up, bout a NOS 242 pretty cheap, hoping they are interchangeable......??

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My car ended up with a bit of a 'franken trans'.  When alpina was racing it, it had a 235/6 with the motorsport gears 2.3->1.  At some point after the car was sold it ended up with a 235/5 gear set 3.36->1 but with a 232 bell and drive shaft.  That gear set is wiped out, the engagement teeth (as I call them) on the gears are chewed up.  The actual gears though are good.  I need to have someone much smarter than me take a good look at the drive shaft- those 'engagement teeth' look a bit worn.  It was common to mate up the back end of a 235/5 with a  232, the only difference is the drive shaft and the bearing size.  Drive shaft has more girth to it.  End goal here is to get a healthy 235/5 put back together.  I have the back end of a JH Getrag that is in excellent condition that I can plug into that 232 bell + the NOS 242 drive shaft.  Eff, I should just send everything to Byron and just say 'make me one and make it work please....'.  I would use the back end of that JH Cr box with the 232 bell and the 242 drive shaft....a real Cr frankentrans for sure.

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The 232 is the early 4 speed from 02s till 1972, with the "Porsche" syncro's.

 

The 242 is the later 4 speed from 02s till 1976 and e21s, with "Borg Warner" syncro's. 

 

The 235 was a close ratio 5 speed available on tii's and turbos, I think they used the early "Porsche" syncro's.

 

They all used the same rough castings for the front and rear cases, the 235 has a extra center section(like the 245 5 speed). The cases look the same on the outside and may have the same #s but are machined differently on the inside. If you look up the part #s for the  input bearings they are different.

 

I think you can use some of the parts but not without machining and/or custom parts.

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Thanks, I made that sound much more complicated than it is.....

 

My Alpina race car had 235/5 sport gears with a 232 bellhousing and drive shaft.  At some point the 235/6 broke and this trans was installed in the car.  I have heard it was common to make the back and center sections from 235/5's with 232 bellhousings (and accompanying driveshaft).  

 

I found a Jensen Healey Getrag CR 5speed, which is the same used by BMW, only the end cap casting doesn't have the bmw numbers, other than that the casting is the same.  This thing was sitting on a guys shelf for 40 years, basically unused, got it for 400 bucks.  Gears, synchro's, bearings are essentially new.  Driveshaft though is for a JH not a BMW.

 

Simple question is whether that 242 driveshaft will work in a 232 Bellhousing.  If so, I can clean up the JH back end (check the synchro's and bearings, clean everything, install the 242 driveshaft then plug the whole thing into that 232 Bell.....whew.

IMG_20210316_145431.jpg

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I’m confused here. When you say driveshaft are you talking about the connection between the transmission and the differential?
 

Just looking at the picture of the gearbox you posted it looks like the Input Shaft from the JH box is longer than the BMW 235/5 input shaft as well as the difference in the spline ( but that is easy enough to deal with).

 

The only other thing you should need to think about is the transmission main shaft. What is the output spline like? Can you just remove the JH drive flange and used the old one from the BMW transmission? It looks to me like the JH gearbox does not have the “Pilot” snout that would keep the driveline centered when using a Guibo coupling.  This is not a good idea!!
 

If what you are asking is “will the main shaft from a 235/5 BMW gearbox fit in a JH 235/5”?  Then I don’t know as I have never had a JH box apart.  The only way to know is completely disassemble both boxes and compare them.  If you have a good main shaft this might work. 
 

At this point you might also check to see if the gears on the  input shafts are the same as well. If you have a good BMW input shaft in your pile of parts you might be able to exchange it as well as the main shaft and wind up with a “real” BMW box when you are done. 

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I'm with Byron- confused.  Are you asking about internal parts, or the connection between the diff and the trans?

 

"242 driveshaft will work in a 232 Bellhousing. "

 

Input shaft?  Counter (lay) shaft?  Main (output) shaft?

 

Again, the 232 and 242 front cases are the same length...

 

t

 

shaft-1.png

Edited by TobyB
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I'm thinking when he says driveshaft he means the input shaft.

 

And the answer is NO. The gears, the input shaft diameter, the bearings and shift rods are all different. You can't just put gears from 2 different transmissions with different ratios into 2 different cases and expect it all to work. Also from what I've heard and read the 235's where not know for strength and you're going to make it weaker with a smaller input shaft.

 

I think you need to do more research and measurements and/or consult an expert.

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I hate to ship sh*t so far away, think I am going to send it over to Retro Engineering in the UK and have them sort out best path forward, maybe a set of straight cut gear retrofit.  Gearbox is the last thing I need to complete my drive train.  I need to get it done.

 

Driveshaft, input shaft.....just  going off of what I see on the BMW catalog.....they call it a 'driveshaft' fwiw.

 

 

Inkeddrive shaft_LI.jpg

IMG_20210403_121742.jpg

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Sorry didn't realize the manual called it a drive shaft, by industry standard its called an input shaft so you don't confuse it with the drive shaft coming out of the transmission to the differential. BMW also sometimes call the drive shaft coming out of the transmission to the differential a propeller shaft.

 

To clarify it would help if you explained the pictures and/or inventory all the parts you have and comparison pictures of parts with labels or captions of parts.

 

Straight cut gears is going to mean more noise, double clutching every shift and probably more maintenance.

 

Don't send anything off yet until you have done more research. I always prefer to take the extra time to do things right the first time, rather than have to do it again.

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The straight cut gear set they offer can either be in a dog set or synchro and are in the motorsport ratio starting at 2.3 vs 3.36.  It isn't inexpensive at about $4500 bucks without shipping.  Noise is not an issue, its going into a race car not a street car.

 

This is what I have:

*Trans that came out of my race car.  235/5 end and center section, sport gears, 232 " " input shaft " " , 232 Bell housing.  Damaged but could be repaired.  Biggest problem with the gears are the engagement teeth (dog teeth?) on the gears.  Trans is completely taken apart.

 

*Jensen Healey/Getrag 235/5 end and center section - complete, steel synchros - not much apparent wear.  The aluminum end and center section are identical to the BMW 235/5 parts, minus the BMW logo cast into the end cap.  The ""input shaft"" is fine spline set up for the JH clutch.

 

*235/5 Bellhousing

 

*235/5 Gear set (donated to the cause from Byron).  Gears were water damaged.  Includes correct 235/5 ""input shaft"".  Gears have some pitting from the water damage, I had all of the REM finished to see how much it helped, actually came out pretty good - but then I am not an expert so my opinion isn't worth much.  The engagement teeth on the gears are much better than the set that cam out of my trans.  According to my BMW parts manager friend, that 235/5 ""input shaft"" is still available from BMW.

 

The best option I think is to take the JH trans, take it apart, replace the bearings, check the synchros and put it back together with 235/5 and correct 235/5 ""input shaft"".  Just need to find the person to do that.

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Consider this:

 

My understanding and research is that the "only" difference between the JH and the BMW is the input shaft, as noted before.

 

So, you should be able to mix and match.

 

I have heard from several sources and here on the FAQ that www.petesgearshop.com in Hayward can rebuild the Getrag. Call them.

 

Alternatively, call Bill Watson at Road Rockets at Sears Point and ask him. Bill rebuilt my Turbo transmission, although his cost was about $5k, and I provided the parts, about 2K. And he wanted to REM for another 2K, which I declined. Bill is familiar with the 235/5 and was able to go through my 235/5 box of parts (literally) and confirm it was all there. Again I declined to have that done due to cost, hence finding Pete's Gears.  Life/ Covid-19 has intervened, so didn't proceed.

 

I have known Bill since the early days of the BMWCCA track events and at the time one of few that I was comfortable had the knowledge to to it right. Yes, very expensive. But Bill has knowledge from restoration and track services for many high dollar BMW race cars.

 

So, give them a call, perhaps take them your boxes of parts, at least they are local.

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...and for what it's worth, the splines on the input shaft aren't magical- 

 

you can always run a friction disc that has the correct hub, as long as the length is right.

 

For a race car, though, a 2.3:1 first gear is kinda....  just about.... perfect.

If you don't do standing starts.

 

t

only uses 1st in the paddock.  

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