Cut and welding a bellhousing from one gearbox to another, any advice?

[Scunderbird]

Evening all,

In my garage currently sits a BMW e60 525d gearbox (GS6-37dz) and an empty casing for a Mustang T45, I'm looking to get the belhousing of the T45 fabbed up to the front of the ZF beemer box, this has become a fairly common sight in the drift scene nad these boxes are being used behind JZs, UZs, RBs, LS, VR6s, Volvo motors and more, I'm looking to use this to make one of, if not the first manual V8 MN12 Thunderbirds in Europe. Personally, I hate driving automatic especially when it's a slow, sluggish 4 speed that just sucks power away from the engine.

I'm trying to find someone who would be able to do either a cut and weld of the two boxes to make one or an adapter plate. What's putting me off adapter plates is then running into the issues of custom flywheels or having to use spacers etc, where as, to my knowledge with a cut and shut I'd be able to use a stock Mustang SN95 flywheel or a lightened aftermarket version, freeing up some more WHP and increasing the responsiveness in the process. Just also to clarify why I didn't jus use a stock ford option is because very few people import manuals, and the ones who do tend to keep them, ontop of that, the Ford tremec boxes outside of a select few are pretty weak to more than stock HP, and with a Scania turbo sitting in my garage waiting, I didn't even want to risk it. (Or pay the 1700 quid shipping fee for an S197 gearbox)

Any advice or insight into this would be greatly appreciated.

 

[FM155]

@PeteMoore Has done a fair few cut and shut bellhousings and is worth asking but might not be interested, because he's done a fair few of them lol...

 

[IL]

Have you checked with all the adapter makers like PMC to see if they do a kit?

 

[finn28]

Nothing to add, but that sounds like a great project and I hope you have a thread going for it in the members section. Be interested to see how it turns out.

 

[Nicky]

Have you the existing box out of the car?

What ratios are you currently running? The diesel car gearbox ratios might be way out from what you need, leaving you to have to change the diff ratio to make this a drivable car without sitting at 6,000rpm in 6th gear at motorway speeds. Another big expense if it’s a rare car and diffs, or at least crown wheels and pinions, aren’t easily got hold of.

You’ll need a clutch to suit the box you’re choosing to use (to match the input shaft), the flywheel you choose to use will need to suit or else be machined to suit the clutch. When the clutch is sorted, you’ll need to take many measurements to get the box the correct distance from the engine so the shaft sits perfectly in the clutch plate, then it’ll be a case of working out where the 2 bellhousings can be cut to get a close mate with each other, or else cut them well back and fill the gap with suitable plating. Another thing to consider at that point is where in relation to your interior/transmission tunnel the gearstick will sit. I’ve seen gearbox conversions done which require a gearstick relocation to move it further back from the dashboard, and even a few in drift cars where the engine was moved so far back that the gearstick had to be mounted on top of the box, much further forward than standard, meaning an intricate and expensive one-off mount. Can you get the interior trim pieces to suit a manual stick if needs be?

With the box mated to the engine and clutch sorted, you’ll also need to cut and join your existing prop shaft to the prop shaft that goes with the new gearbox, so more custom work.

With the prop sorted, you’ll also have to fabricate a suitable gearbox mount, along with modifying the tunnel.

Something else to consider is the speedo. Is your speedo driven off the existing box? If so, is there a speedo output on the new box, can it be used with the current dash and can you get it to work/convert it properly? Also, as with any auto to manual conversion, what wiring will need modified to allow the car to start without the auto stick being in P or N; can you just leave the gear selector plugged in and bury it behind the dash or under the car in the P/N position? Will you be able to get a power signal for the reverse switch to use reverse lights?

A clutch pedal, master cylinder and slave cylinder will also need to be sourced, mounted and plumbed in. Is a pedal easy fit for your car or will in be a case of using a pedal from something else and modifying it to suit?

There’s likely other things to consider too, but weigh all of that up and see where you stand as it may actually turn out to be a lot cheaper, less laborious and less of a headache to stick with original equipment from your car than opting for a conversion from a different manufacturer.

Apologies for the long winded post, but those kind of things are often overlooked if you haven’t done a conversion before.

 

[natogreen16v]

Apologies for the long winded post, but those kind of things are often overlooked if you haven’t done a conversion before.

**** apologising. This is sound advice

 

[Nicky]

**** apologising. This is sound advice

It’s a bit like people buying a turbo off eBay at £120 thinking they are going to do a turbo conversion on a car without thinking about literally everything else that’s required.

The turbo is a small component among sorting the oil feed/return (is the oil pump capable of supplying more oil), water cooling the turbo (if needed), additional engine cooling (bigger rad/high flow waterpump/uprated stat/oil cooler etc), are the existing exhaust studs strong enough to hold a turbo manifold or will they need beefed up, routing the downpipe (making sure there’s room for the turbo and downpipe would be an early consideration), upgrading the entire fuel system (injectors, pump, regulator etc), intercooler and pipe work if necessary, boost control, ECU, someone to map it, compression (thicker head gasket, pocketed pistons etc), will the engine internals cope with forced induction etc…

I suppose all of that’s relevant too as the OP mentioned a turbo too…

 

[natogreen16v]

Someone find @Nicky a crown

Nah for real though, detailed responses like this on forums are worth their weight in gold and should be the norm.

 

[cauld1]

It’s a bit like people buying a turbo off eBay at £120 thinking they are going to do a turbo conversion on a car without thinking about literally everything else that’s required.

The turbo is a small component among sorting the oil feed/return (is the oil pump capable of supplying more oil), water cooling the turbo (if needed), additional engine cooling (bigger rad/high flow waterpump/uprated stat/oil cooler etc), are the existing exhaust studs strong enough to hold a turbo manifold or will they need beefed up, routing the downpipe (making sure there’s room for the turbo and downpipe would be an early consideration), upgrading the entire fuel system (injectors, pump, regulator etc), intercooler and pipe work if necessary, boost control, ECU, someone to map it, compression (thicker head gasket, pocketed pistons etc), will the engine internals cope with forced induction etc…

I suppose all of that’s relevant too as the OP mentioned a turbo too…

Great advice.

I know what killed off my turbo ambitions for the E34 was none of this, as there's a wealth of info on turboing an M50 out there. It was the thought of adding a load of other stuff into an engine bay I'd spent a load of time tidying

 

[Nicky]

Great advice.

I know what killed off my turbo ambitions for the E34 was none of this, as there's a wealth of info on turboing an M50 out there. It was the thought of adding a load of other stuff into an engine bay I'd spent a load of time tidying

Aye, the popularity of the M50 turbo conversion means there’s plenty of parts now readily available for them, even various styles of manifolds such as log manifolds to mount the turbo at the front of the engine top mounts for a bit of visual porn and ease of routing for pipe work.

That thing of yours would look well with a polished Holset blower poking out through a hole in the bonnet…

 

[cauld1]

Aye, the popularity of the M50 turbo conversion means there’s plenty of parts now readily available for them, even various styles of manifolds such as log manifolds to mount the turbo at the front of the engine top mounts for a bit of visual porn and ease of routing for pipe work.

That thing of yours would look well with a polished Holset blower poking out through a hole in the bonnet…

I've a log manifold and hx35 sitting here a few years now

 

[Nicky]

I've a log manifold and hx35 sitting here a few years now

Flush the log. Twin scroll tubular manifold or bust!!!

 

[Scunderbird]

Have you the existing box out of the car?

What ratios are you currently running? The diesel car gearbox ratios might be way out from what you need, leaving you to have to change the diff ratio to make this a drivable car without sitting at 6,000rpm in 6th gear at motorway speeds. Another big expense if it’s a rare car and diffs, or at least crown wheels and pinions, aren’t easily got hold of.

You’ll need a clutch to suit the box you’re choosing to use (to match the input shaft), the flywheel you choose to use will need to suit or else be machined to suit the clutch. When the clutch is sorted, you’ll need to take many measurements to get the box the correct distance from the engine so the shaft sits perfectly in the clutch plate, then it’ll be a case of working out where the 2 bellhousings can be cut to get a close mate with each other, or else cut them well back and fill the gap with suitable plating. Another thing to consider at that point is where in relation to your interior/transmission tunnel the gearstick will sit. I’ve seen gearbox conversions done which require a gearstick relocation to move it further back from the dashboard, and even a few in drift cars where the engine was moved so far back that the gearstick had to be mounted on top of the box, much further forward than standard, meaning an intricate and expensive one-off mount. Can you get the interior trim pieces to suit a manual stick if needs be?

With the box mated to the engine and clutch sorted, you’ll also need to cut and join your existing prop shaft to the prop shaft that goes with the new gearbox, so more custom work.

With the prop sorted, you’ll also have to fabricate a suitable gearbox mount, along with modifying the tunnel.

Something else to consider is the speedo. Is your speedo driven off the existing box? If so, is there a speedo output on the new box, can it be used with the current dash and can you get it to work/convert it properly? Also, as with any auto to manual conversion, what wiring will need modified to allow the car to start without the auto stick being in P or N; can you just leave the gear selector plugged in and bury it behind the dash or under the car in the P/N position? Will you be able to get a power signal for the reverse switch to use reverse lights?

A clutch pedal, master cylinder and slave cylinder will also need to be sourced, mounted and plumbed in. Is a pedal easy fit for your car or will in be a case of using a pedal from something else and modifying it to suit?

There’s likely other things to consider too, but weigh all of that up and see where you stand as it may actually turn out to be a lot cheaper, less laborious and less of a headache to stick with original equipment from your car than opting for a conversion from a different manufacturer.

Apologies for the long winded post, but those kind of things are often overlooked if you haven’t done a conversion before.

I appreciate the concerns here, I have looked into a lot of this and a lot of things mentioned here are issues I have mulled over for some time, the reason I chose this gearbox are its size which compared to a T45, T56 etc is physically about the same, so no tunnel bashing, the other benefit is that the BMW boxes are remote factory shifter, so I can fab something up to make work in a factory shifter location I already have a chassis mounted shifter I plan on using. I did use a gear ratio calculator too to work out if my factory diff can take it, which seemingly, I should be alright, if needs be I can down the ratios to match the E60 525d the box came from.

Luckily, these are kind of just parts bin specials, they use the same 8.8 diffs as in many other Ford products of the time, changing ratios is neither hard not particularly costly even for an LSD, regardless of I use a factory Ford box or not I would have to change the driveshaft, so that's an expected expense I can even use the cobra rear solid bushings to stiffen it all up. The ECUs on these are pretty easy to flash to get the car to recognise that they are now manual. As for wiring, my dad was an electrician for 30 years and I'm fortunate enough to know some very talented restoration people (who are also willing to help with the shop space and a hand for the swap).

There's a lot of info and guides out there already on manual swapping these cars and the only real difference is that I'm not using a stock Ford box. I chose the GS6-37DZ for many reasons, it takes high power, it's easily and cheaply replaced and most of Fords offerings outside of the T56 Magnum (which you're talking 3k+ for) they don't hold up to the power I aim for in future.

I'm not big on keeping a cars originality either, I think giving it a completely unique look/feel/driving experience is more important. So I'll probably end up going a custom route with gauges, as for the centre console the Supercoupe (3.8 Supercharged V6) came in manual for this generation, the mounting points for stuff like a master cylinder for the hydraulic clutch are threaded on the chassis from factory, Ford did plan on making a 32v supercharged V8 mated to a T56.

Also planning on buying a later "PI" 2v to build with some forged internals ready for boost, which I've done a fair bit of research into what works with what.

I understand that this seems a more roundabout way to do a manual swap, I understand it's not going to be straightforward.

I appreciate the concerns here, I have looked into a lot of this and a lot of things mentioned here are issues I have mulled over for some time, the reason I chose this gearbox are its size which compared to a T45, T56 etc is physically about the same, so no tunnel bashing, the other benefit is that the BMW boxes are remote factory shifter, so I can fab something up to make work in a factory shifter location I already have a chassis mounted shifter I plan on using. I did use a gear ratio calculator too to work out if my factory diff can take it, which seemingly, I should be alright, if needs be I can down the ratios to match the E60 525d the box came from.

Luckily, these are kind of just parts bin specials, they use the same 8.8 diffs as in many other Ford products of the time, changing ratios is neither hard not particularly costly even for an LSD, regardless of I use a factory Ford box or not I would have to change the driveshaft, so that's an expected expense I can even use the cobra rear solid bushings to stiffen it all up. The ECUs on these are pretty easy to flash to get the car to recognise that they are now manual. As for wiring, my dad was an electrician for 30 years and I'm fortunate enough to know some very talented restoration people (who are also willing to help with the shop space and a hand for the swap).

There's a lot of info and guides out there already on manual swapping these cars and the only real difference is that I'm not using a stock Ford box. I chose the GS6-37DZ for many reasons, it takes high power, it's easily and cheaply replaced and most of Fords offerings outside of the T56 Magnum (which you're talking 3k+ for) they don't hold up to the power I aim for in future.

I'm not big on keeping a cars originality either, I think giving it a completely unique look/feel/driving experience is more important. So I'll probably end up going a custom route with gauges, as for the centre console the Supercoupe (3.8 Supercharged V6) came in manual for this generation, the mounting points for stuff like a master cylinder for the hydraulic clutch are threaded on the chassis from factory, Ford did plan on making a 32v supercharged V8 mated to a T56.

Also planning on buying a later "PI" 2v to build with some forged internals ready for boost, which I've done a fair bit of research into what works with what.

I understand that this seems a more roundabout way to do a manual swap, I understand it's not going to be straightforward.

Just adding on, I also know nothing with cars is cheap or quick! I don't mind the build taking longer, as long as it's done right