5 speed swap help

[Rusty525rusty]

Hi all,

I'm just starting out on my 5 speed swap. 

I have a 1502 1976 RHD in UK. The 5 speed box I have found is a 240 from e21 with speedo cable.

Everything I have read about 5 speed swaps suggests I will need to make a shorter prop, at first it looks like the e21 prop I have is a few cms shorter (hand measure 02 original at 1598 vs e21 at 1545). However link below suggests the 240 is actually shorter then original 02 4 speed? So needing a longer prop?

Gearbox types | BMWE21.net – Jeroen's BMW E21 Network

WWW.BMWE21.NET

I'm not actually able to get the box out to compare size until next weekend but thought I would try a post here in the mean time. Anyone tried a 240 box swap?

Thanks

[Rusty525rusty]

[Dudeland]

You need to shorten the driveshaft.  Sorry, I know it sucks, and you would like to finish it in a weekend, but no.  I think there is a swap service on this side of the pond, but not in "ye ol crumpet town" (LOL).  

 

Enjoy the process. Perhaps change the oil before you plunk it in.  Make sure the upper drain plug comes out, as installing it, draining it, and not being able to refill it sucks. 

 

Regards

 

 

 

[tech71]

On 1/2/2024 at 12:05 PM, Rusty525rusty said:

Anyone tried a 240 box swap?

That would be me I guess however, my knowledge is based on a US spec 2002, not sure how it applies to a RHD Euro spec 1502😉

My car is a US spec 1976 2002, came stock with a Getrag 242.

I installed a Getrag 240 from a US spec 1985 E30 318i 

There are a few differences from the trans you have ( 2 aft mount points, no speedo drive) but I suspect the dimensions (specifically the length) will be the same .

On 1/2/2024 at 12:05 PM, Rusty525rusty said:

However link below suggests the 240 is actually shorter then original 02 4 speed? So needing a longer prop?

In my case the 240( at the output flange) was a few cm longer that the original 4 speed so a slightly shorter prop shaft was required, this is normally accomplished by shortening the cars original prop shaft and modifying it by fitting the 3 bolt flange from an E21 prop shaft to it by welding. It must also be balanced after being modified, that parts important.

Hopefully there is a specialist shop(propellor shafts) over there that can do the work.

There is a hack that allows you to use a Prop from an E30 but the center bearing support mount has to be modified by fabricating an extension mount.

The E30 shaft has a sliding sleeve the can be adjusted to length.

Thats the route I took because I had a shaft from an  US spec 85 318i E30.

I did the entire swap in my garage, used an slightly shortened e21 shift platform, lengthened the shift rod.

I'm  fairly well equipped for a DIYer  with compressor, welder, air tools ect.

Are you hoping to do the swap yourself? 

Edited January 4 by tech71

[Rusty525rusty]

Thanks for the helpful replies. I wanted to understand I am on the right track. But had wondered if some how i was in a better position with the 240 box. Yeah I will be doing the work myself or at least that's the plan. I will get the box out on Sunday and then be able to do the same side by side comparisons. I guess I will offer the 240 box up for sizing. Then probably try to source e21 shifter mech.

Next to find a place to shorter the prop.

Is changing to the 3 bolt an absolute must do? My 4 bolt looks in perfect condition. Power wise i am just 100bhp, no rocket ship.

Thanks. I will post my updates.

[ExpensiveHoby]

18 hours ago, tech71 said:

That would be me however, my knowledge is based on a US spec 2002, not sure how it applies to a RHD Euro spec 1502😉

My car is a US spec 1976 2002, came stock with a Getrag 242.

I installed a Getrag 240 from a US spec 1985 E30 318i 

There are a few differences from the trans you have ( 2 aft mount points, no speedo drive) but I suspect the dimensions (specifically the length) will be the same .

In my case the 240( at the output flange) was a few cm longer that the original 4 speed so a slightly shorter prop shaft was required, this is normally accomplished by shortening the cars original prop shaft and modifying it by fitting the 3 bolt flange from an E21 prop shaft to it by welding. It must also be balanced after being modified, that parts important.

Hopefully there is a specialist shop(propellor shafts) over there that can do the work.

There is a hack that allows you to use a Prop from an E30 but the center bearing support mount has to be modified by fabricating an extension mount.

The E30 shaft has a sliding sleeve the can be adjusted to length.

Thats the route I took because I had a shaft from an  US spec 85 318i E30.

I did the entire swap in my garage, used an slightly shortened e21 shift platform, lengthened the shift rod.

I'm  fairly well equipped for a DIYer  with compressor, welder, air tools ect.

Are you hoping to do the swap yourself? 

 

Can you please let us know the difference in flange lengths? Specifically the distance between the bell housing side of the two aluminum bars. I am also doing a 240 swap into my '73 and from what I have measured the difference in the length from bell housing to far side of guibo is 48mm (1.88"). This means the original prop shaft has to be shortened by 48mm.

[ExpensiveHoby]

14 hours ago, Rusty525rusty said:

Thanks for the helpful replies. I wanted to understand I am on the right track. But had wondered if some how i was in a better position with the 240 box. Yeah I will be doing the work myself or at least that's the plan. I will get the box out on Sunday and then be able to do the same side by side comparisons. I guess I will offer the 240 box up for sizing. Then probably try to source e21 shifter mech.

Next to find a place to shorter the prop.

Is changing to the 3 bolt an absolute must do? My 4 bolt looks in perfect condition. Power wise i am just 100bhp, no rocket ship.

Thanks. I will post my updates.

The prop shaft you install needs to have the flange that matches the output of the G240 that you have regardless of what it is. Easiest thing to do is to take the prop shaft from the 2002 and get it cut to the shorter length and weld on the flange of the prop shaft that was originally mated to the G240.

[Son of Marty]

The 3 hole guibo has proved to be much stronger than the 4 hole, so the 3 hole is the go to if you have the parts.

[tech71]

2 hours ago, ExpensiveHoby said:

Can you please let us know the difference in flange lengths?

Sorry, I cant give an exact figure on that. Think it was around 3/4 in

I decided that calculating driveshaft length by subtracting the difference in overall trans lengths would be unwise. Better to measure precisely from face of diff output flange, to face of installed guibo on trans output shaft.

As I said, I ended up adapting a driveshaft from an 85 318i by fabricating an extension mount for the CSB mount, no cutting or modifying to the actual driveshaft was required. Attaches to original CSB mounts, requires drilling 2 holes in your car, completely reversible😉

So I am not well versed on shortening the original shaft, Sorry to muddy the water.

As far as I am concerned, if a DS from an M10 E30 can be obtained, its the way to go.

 

Edited January 3 by tech71

[tech71]

This may be of interest but strongly recommend measuring as discribed above to verify this info.

Edited January 15 by tech71

[ExpensiveHoby]

Thanks @tech71  I did see that diagram but my measurement is giving a slightly different number. But I believe variability can be accounted for by the movement of the diff and CSB. 

 

FYI - I would confidently alter the original prop shaft by measuring the difference in the transmissions. If the original shaft worked properly for 50 years, subtracting the difference between the transmissions at the installed guibos has to mathematically work. 

[jimk]

I trust the math.  If the stock driveshaft fit, one with a calculated length will be as accurate.

 

Measuring is a crap shoot.  The dif needs to be at the right place in it's for/aft adjustment slots.  The slots are there to allow for the tolerance buildup with all the parts in the car and the chasis too.

 

Be sure to allow for the difference in thickness between an 8 bolt guibo and a 6 bolt one.

 

Attached are the driveshaft length specs for oe driveshafts.  And contrary to some thinking they were not selectively fit at the factory, no time  on an assembly line to pick from the pile.

 

[ExpensiveHoby]

I saw these dimensions on another chat and was confused why my manual which I downloaded from this website lists the “B” as 959mm and not the 956mm shown above. Curious as to why the 3mm change. 

[JQ02]

So an overdrive 5th gear with a built engine at full song might exceed the speed limit of the driveshaft. 🤔

At least there's breathing room for torque

[tech71]

1 hour ago, jimk said:

I trust the math.  If the stock driveshaft fit, one with a calculated length will be as accurate.

Cant argue that, at least not successfully😉

Guess I should have recorded an accurate measurement there but when I started eyeballing the E30 shaft laid up against my stock 4 speed shaft, I got distracted and shortly after, abandoned the shortening plan altogether.

Edited January 4 by tech71