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Old 08-06-2019, 06:46 AM   #1
bugjam1999
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Default Adjustable Torque Rods before Measuring Propshaft - or negligible?

Hi all,

Perhaps I’m over thinking this – I’ve got a 240 that I turbo converted back in 2015. Over the last couple of weekends I took the engine with attached (and increasingly rattly) M47 out, then refitted it with an M90 – of course now the propshaft is too short. My thinking so far has been that I should fit adjustable torque rods and set the diff angle correctly before measuring the gap and then having the propshaft lengthened, but thinking still further perhaps the difference in length will be negligible, or taken up by the sliding joint, or the rear section of the prop shaft will slide into the front section meaning the distance from the prop carrier bearing to the gearbox output flange will remain the same regardless…

Any thoughts? Am I overthinking? I measured the gap as it is, which unsurprisingly enough is 50mm – the difference in length between the two gearboxes.

For completeness- the car is lowered 40mm on lowering springs. I haven’t made an adjustable panard bar yet.
Cheers

Last edited by bugjam1999; 08-06-2019 at 06:49 AM.. Reason: Added lowering detail
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Old 08-06-2019, 05:21 PM   #2
Lankku
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You have to modify or change only the front half so what ever happens to the rear suspension won't affect that part.
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Old 08-07-2019, 02:04 AM   #3
bugjam1999
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Great, thanks- thatís the answer I was looking for.

Iíll take it off and get it lengthened.

Cheers
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Old 08-07-2019, 02:10 AM   #4
K9 240
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I am planning on using a M90 in my 240 & was going to use this...
http://www.retroturbo.com/?product=v...lvo-200-series
with a modified support bracket to the original crossmember.
I haven't bought it yet so can't comment on quality or fitment.
Tim
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Old 08-07-2019, 10:36 AM   #5
bugjam1999
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Tim,

Yep- Iíve seen that too, also I know someone via the forums (they might comment on this) that fitted one a couple of years ago and hasnít had any issues. Although quite expensive for what it is, itís cheaper than the quotes Iíve been getting for having the propshaft lengthened... which have ranged from £100 to £180, and the spacer will turn up in the post- although post to the uk is £15 :o

For a bracket buy this: https://www.classicswede.co.uk/M90_g..._17476331.aspx

Cheers
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Old 08-07-2019, 04:20 PM   #6
JW240
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For the M90 swap of my 240 I used the front end of a M47 equipped 740/940. That front piece is 80mm longer than one of a 240 with the same drive train. M90 is indeed 50mm shorter than M47 so subtract those dimensions and you end up with a drive shaft that needs to be shortened 30mm. That was cheaper (because easier) than taking the original 240 drive shaft and have a new section of tube welded in place. Shop checked the balancing and it was fine combined with the 240 rear piece. Maybe that helps. Oh and better a tad more play than too little..
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Old 08-08-2019, 03:21 AM   #7
bugjam1999
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Ah, I hadnít thought of that- but it makes sense that shortening a propshaft would be cheaper. That said, I donít have a 940 front section to hand, so unless someone randomly gave me one itís still going to be cheaper overall to have my existing propshaft lengthened.

Better a bit too much play that too little- better to extend it 45mm if I was struggling to measure it accurately?

I have the tools to measure accurately- the suggestion of 45mm above is just to make sure I understand correctly.

Cheers
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