235/5 CR Trans

[visionaut]

https://www.mcmaster.com/products/bearings/

[kbmb02]

A consideration worthy (perhaps) of discussion here is the type of giubo (a/k/a/ flex disc) which will be used?

 

In my experience, the strength and suitability of “8 bolt” giubos is marginal in race applications; and when they break under duress, damage often occurs. It’s for that reason that I’m swapping to 6 bolt giubo and driveshafts, as shown here with a custom-fabricated 3 prong output flange for a 4 speed (which is not the same as a 235 or 245 5 speed flange). -KB

 

Edited December 6, 2023 by kbmb02
Added the photo I forgot to upload.

[markmac]

Ken, it is a really good point, drive shaft is on the list as well.  At one point (a long time ago), I had some dialog with Byron (Preyupy) about this.  If I remember correctly, his recommendation was to use a 'yoke' assembly of sorts as the trans output flange (in lieu of) and then it would be matched up on the drive shaft end to work together (duh).  I want to say that he had some high hp CSL's that used this arrangement in lieu of the flex guibo.  Again, if I remember correctly those were being used with ZF S5/18-3 transmissions.

[markmac]

And there you have it....

 

ZF S5-18/3 — Elite Racing Transmissions

WWW.ELITERACINGTRANSMISSIONS.COM

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Elite’s ZF 18/3 5 speed gearbox. 300ftlbs torque capacity. Fully homologated synchromesh or dog engagement for use in historic rally applications and more. All parts (bar gearing), are interchangeable with original ZF S5-18/3 gearboxes. Elite’s gears are REM Superfinished, as...

 

[uai]

36 minutes ago, markmac said:

And there you have it....

 

ZF S5-18/3 — Elite Racing Transmissions

WWW.ELITERACINGTRANSMISSIONS.COM

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Elite’s ZF 18/3 5 speed gearbox. 300ftlbs torque capacity. Fully homologated synchromesh or dog engagement for use in historic rally applications and more. All parts (bar gearing), are interchangeable with original ZF S5-18/3 gearboxes. Elite’s gears are REM Superfinished, as...

 

That's not that epensive taking into consideration that I paid 5000€ for a rebuilt used one.
If they supply any ratios you want it's even cheap
The holinger is more pricey
https://www.holinger.de/showroom/hzf

Edited December 5, 2023 by uai

[Preyupy]

I have 2 of the Elite ZF S5 18/3 gearboxes we use on a Gp2 CSL and I can highly recommend them.  The output is not the same as the BMW based gearboxes (this car came with a BMW version of the close ratio ZF 5 speed that did use an output flange and the larger 6 cylinder Guibo coupler)  it uses a sliding Yoke style output shaft that I adapted to a custom drive shaft that uses U-joints.  The biggest problem you wil have it they are built to bolt to a Ford Cosworth bell housing not the standard BMW pattern.  I had to modify a bell housing to fit as well as have them build the gearbox with an imput shaft with the correct length, spline and pilot size.  They are a racing box including the synchro boxes,  the gears are not straight cut teeth but they are not a full helical cut either and as such would be a bit noisy in a street car.  

[kbmb02]

The ZF S5 boxes we run have the proper (matching) bell housing, input shaft and large, 3 prong output flange - I’ll look at links later, perhaps we’re paying a high cost for mostly plug + pay + race. -KB

[Preyupy]

They are quite accommodating and IF you have an original BMW ZF S5 transmission with a good housing they can fit their new internals and you have a proper box for your BMW.  They will need to make a custom main/output shaft as the new boxes are designed around the sliding yoke used in the Ford applications. 

 

If you do not have an original BMW ZF gearbox they can't make you one as they don't have the cases.  I even tried to send them a front section from a ZF 4 speed that uses the same front housing as the 5 speed but it will not match up with their new castings. 

 

As I said the modifications to a bell housing is not all that difficult with some proper welding and machining skills.  The sliding yoke output gets rid of the Guibo as well.  Just remember it is designed to be a racing gearbox.  It's strong, you can get repair parts easily BUT it is noisy and you won't like it in a street car unless you are a deaf as me or wear ear plugs.   

[markmac]

For me, at the moment anyway is getting the car up and running.  Alpina didn't race it (as far as I know) with a 235/5.  Even though the ZF trans was homologated for Gr2 racing, I am guessing Alpina used the 235/6 with motorsport gears (2.3------->1).  I don't know that I have seen a detailed write up on that part of the car.  

 

Clutch slave cylinder.  I have the one that came with the car.  It's all cleaned up and 'looks' good.  Is there any way to test one of these?  They aren't that expensive to replace (so then the answer is just replace it I guess).  Still, I would rather not spend another hundred bux if I don't have to.

[tzei]

Rig it with a pressure meter. About 500 psi meter should cover it. I guess line pressure is around 350 psi and you can do the math if needs be. Push & hold a few times and if no leaks appears you’re good to go.

 

me thinks

[edgefinder]

Markmac, I've waited to reply because I didn't know enough, Toby's suggestion to add a ring is good but kbmbo2's 3 prong flange is the way to go if it meets the rules. I'll be watching to see what the final plan is

[markmac]

Update on output flange, email this morning from WN that the part is back in stock, they sent me an invoice with it, sent them a note back that I wanted a half dozen other fiddly parts associated with the trans, revised quote (within 10 minutes), paid, order is going out today.

 

Platinum Start A+++ to them for their customer service.  I haven't ever purchased from them before so I am pretty pleased.

 

[My stupid mistake for panicking about finding that part, should have just emailed them, instead I paid 2x for it]

Edited December 8, 2023 by markmac

[JohnP_02]

WN part for future reference:

 

https://www.wallothnesch.com/en/output-flange-14-splines-for-getrag-235-5-speed-sport-gearbox-for-all-models-and-years-of-production-you-need-1-for-1-car-23-25-03.html

Edited December 12, 2023 by JohnP_02

[Anthony]

@markmac I agree with @kbmb02. The 8 bolt guibo is not suitable for track. If you want to retain originality go ahead but be prepared to replace just about every weekend and even then you may have one come apart. The 6 bolt guibo is much stronger. 

Metric Mechanic has remade the 6 bolt flange for the 235/5 box - they use them on their builds and if they will sell you one I would suggest this. I have seen enough collateral damage from guibos exiting the chat that it seems it would be the time to do it. 

[TobyB]

...time for a Jerico, methinks...

 

 

t

then you can have 4 useful gears