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Old 06-03-2020, 06:10 AM   #1
740stu
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Default 740Turbo (M46) to M90 Conversion

Hi,
I've been going through the forum here and others online to look at converting my newly purchased 740 turbo gearbox.

It is currently stock but am going to try and get it up to the 300HP margin - for this I have found the the M46 gearbox are as useful as a chocolate teapot.

So looking to swap to a M90 gearbox if you guys think this will be up to the power/torque generated?

I have found a load of posts on what people say you need and conversions but seems like there is some differences with clutches and flywheels etc?

Was wondering if someone could make me a parts list for what would be required?

I think it would be the below?

M90 gearbox + shift lever
M90 gearbox rear mount bracket/bridge
M46 clutch disc and flywheel or 850 clutch and M46 flywheel
Bolts etc from gearbox
740/760 complete drive shaft

If anyone has images of there conversion it would be amazing!

Base in the UK

Thanks

Stuart
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Old 06-03-2020, 01:11 PM   #2
shoestring
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https://forums.turbobricks.com/showthread.php?t=345277

This is on a 940, I would imagine it is EXTREMELY similar.
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Old 06-04-2020, 04:32 AM   #3
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The M90 gearbox was never sold in the US, so you might be better off asking on the UK Volvo Owners club forum.
What you are trying to do is very straight forward, it's what Volvo themselves did when they introduced the M90 in the 940 (which is a 740 in all but name).

All you need is a donor car. BUT, if you really are aiming for 300bhp, the standard clutch won't be much use to you. Investigate the TTV flywheel and 850R clutch combination.
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Old 06-04-2020, 05:19 PM   #4
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Quote:
Originally Posted by 740stu View Post
Hi,
I've been going through the forum here and others online to look at converting my newly purchased 740 turbo gearbox.

It is currently stock but am going to try and get it up to the 300HP margin - for this I have found the the M46 gearbox are as useful as a chocolate teapot.

So looking to swap to a M90 gearbox if you guys think this will be up to the power/torque generated?

I have found a load of posts on what people say you need and conversions but seems like there is some differences with clutches and flywheels etc?

Was wondering if someone could make me a parts list for what would be required?

I think it would be the below?

M90 gearbox + shift lever
M90 gearbox rear mount bracket/bridge
M46 clutch disc and flywheel or 850 clutch and M46 flywheel
Bolts etc from gearbox
740/760 complete drive shaft

If anyone has images of there conversion it would be amazing!

Base in the UK

Thanks

Stuart
You only need the front half of the driveshaft. If replacing a hydraulic clutch M46 it basically goes in where the M46 went. The clutch friction disc has a different number of splines for the M90 so will need to be replaced with one from a 940 TDi.

I have lots of pictures and documentation of my swap from auto to M90 in the previously posted thread. (including a list of parts, sources, and prices)

What year is your car? I believe earlier cars have a 215 mm clutch disc instead of the later (1989 and up) 228 mm piece.
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Old 06-06-2020, 01:44 AM   #5
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Stock those m90s come with a dual mass flywheel so don't use that. People ditch that. Get the TTV flywheel for 850R clutch 240mm for m90. What I did...

http://ttvracing.com/product/volvo-b...o-850r-clutch/

OR use stock cast iron flywheel and do this..




Also here is your UK volvo connection he even sells them. Hit him up for info.

https://www.classicswede.co.uk/B200_..._14964734.aspx
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Last edited by sbabbs; 06-06-2020 at 01:49 AM..
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Old 06-06-2020, 02:49 AM   #6
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You might consider using another box like bmw and weld it up behind ur redblock
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Old 06-06-2020, 02:44 PM   #7
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We'll over there in UK or europa you can get those diesel bmw transmissions and the adapter plate from KL racing I think. Not so much here in the states unless you can find the old bmw getrag 265 with removable bellhousing. I got that in my 90 745 with JohnV billet steel 240mm flywheel uses saab areo 9000 pressure plate. Use the volvo bellhousing and adapter plate between that and tranny.

Yeah lots of options.

Did you watch my damage video above? THat was a bmw getrag 265 transmission that got destroyed when the cast iron flywheel exploded...
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Old 06-07-2020, 06:25 AM   #8
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For 300hp at the crank both gearboxes are capable of handling that, just drive with a little respect for the transmission or you will damage gearboxes and axles.

Clutch wise you are likely to be past the limit of the diesel clutch and near the limit of the TTV combined with 850R clutch

The original dished flywheel, you are not super likely to have it shatter but it can and does happen. Theworst thing about the dished flywheel is how heavy it is, changing to a lighter flywheel offers a great improvement in engine response
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Old 06-07-2020, 02:25 PM   #9
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Make....
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Last edited by ZVOLV; 06-09-2020 at 01:52 PM.. Reason: Wrong thread
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Old 06-07-2020, 05:33 PM   #10
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Quote:
Originally Posted by ZVOLV View Post
Make sure the kickdown cable is adjusted and working properly.
replying to the wrong thread?
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Old 06-16-2020, 04:53 AM   #11
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The m46 to m90 conversion in a 740 is really straightforward and it'll hold 300HP and 450NM with the right pressure plate. And don't even think about getting a sintered 6-puck disc! They're not necessary and just a pain in the rear if it's your daily driver. Heard enough people complaining about their OP setup when they get to driving it as a daily...

M90 gearbox + shift lever -- yeah
M90 gearbox rear mount bracket/bridge -- yeah
M46 clutch disc and flywheel or 850 clutch and M46 flywheel -- Sachs 1862 314 032 fiber disc and a Sachs 883082 999763 pressure plate with the stock M46 Dogdish flywheel
Bolts etc from gearbox -- yeah
740/760 complete drive shaft -- needs to be from a car with the M90, and get the whole thing! Two piece driveshafts are balanced at the factory, don't mix and match.

I didn't take a lot of pictures with my swap, but like I said, it's a very direct replacement with the right parts.

More detailed info can be found here: http://forums.turbobricks.com/showthread.php?t=94325
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Old 06-16-2020, 05:14 AM   #12
740stu
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thanks everyone!
I have two options now I am currently looking at:
M90 as said as that seems very straightforward easy bolt and unbolt
or
conversion to a ZF BMW gearbox as mentioned
seems like the ZF conversion just takes BMW clutch, gearbox with the need to cut the bellhousing and weld the front of the bellhousing of an M46/7 to it to match the redblock.
I can get the new mounts fabricated or purchase from here pretty cheap...https://www.anderssonsteelspeed.se/lang-EN/webshop and then a custom prop made or my existing one modified.
Just tryign to figure out the best ZF gearbox - would love an e36 328i box rather than the 320d one...but will have to look at price an availability.
Also not sure what flywheel to use with this gearbox.
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Old 06-16-2020, 03:24 PM   #13
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Welp here is one that would fit and work.

http://ttvracing.com/product/volvo-b...facturer=volvo


THat M90 ttv one only fits in m90 they say..

http://ttvracing.com/products/?manuf...type=flywheels

Simon
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Old 06-16-2020, 08:57 PM   #14
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In addition to the aspects you are already looking at (fit, availability, power handling, etc.) need to consider the gear ratios-- if they are going to be appropriate to your planned power and torque bands, and driving style and environment. Otherwise you may be severely disappointed in the end, after all the hard work.
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