Custom Gearbox Bellhousing

[Aragorn]

Ok so i've finally reached the point in the project where i need to start having things machined up and welded together to mate my Audi motor to the landrover transmission.

I have an idea in my mind what i want to do but i want to see what you chaps think of it first!

As it stands i have the front 2" of an Audi manual transmission:

http://www.lr90.org/gallery2/main.php?g2_v..._serialNumber=2

And the bellhousing from a discovery V8:

http://www.lr90.org/gallery2/main.php?g2_v..._serialNumber=2

My thaughts as it stands go as follows; Obviously the Audi housing needs to be milled flat, the discovery housing needs shortened by the height of the audi housing + 5mm (the input shaft sits 5mm further away from the BH face on the R380 with disco housing than the original audi box did)

Due to the differences in shape i planned to use a piece of alloy plate, perhaps 8mm thick, between the two halves and weld each half to that, using an LT77 casing and a faux input shaft as a jig:

http://www.lr90.org/gallery2/main.php?g2_v..._serialNumber=2

The faux input shaft will be milled to fit tightly inside the clutch housing, and measure the same length as that on the R380 box to give me a jig i can use to get the bellhousing centre aligned with the crank centre.

The problem ive noticed is that once i've welded on the alloy plate i wont be able to get to the bolt holes on the original housing, so i wont be able to bolt the assembly to the engine.

My next thaughts were to use two pieces of alloy plate instead of one, with the two pieces doweled and bolted together before being welded to the bellhousings as before, this way i can unbolt the two halves, bolt the "flywheel housing" onto the engine first, then bolt the bellhousing part back on.

So whats peoples thaughts on that? Is there any easier method? am i going along the right lines here?

Thanks

[Guest noggy]

why cant you drill holes in the alloy plate so you can use the holes on the housing? or am i missing something?

and you start talkin about a disco v8 gearbox which is the LT77 then drift off and talk about the R380...

what drive line are you tryin to achieve?

[Night Train]

Any reason why a replacement engine backplate can't be made to fit the Disco bell housing to the Audi engine? I can't see your links.

[Night Train]

You could cut the Audi housing flange off then cut away all of the Disco housing up to the front of the gear box and refabricate the bit in the middle to suit length and clearance as required.

[Aragorn]

noggy: the disco housing is larger than the Audi one, so once they're welded together the bolt holes would be inside the housing.

for clarification, i have a Defender TDi R380, and a bellhousing from a Disco V8 (LT77). I need the V8 housing due to the clutch slave position being on the opposite side, using the TDi bellhousing would have meant the clutch slave was in the middle of the audi starter motor. The LT77 main casing i have came from the disco V8, and i will only be using this as a jig to centralise the bellhousing round the crank before welding.

Night train: The disco housing is already too long, so an additional adaptor plate between the two wont work, and the audi engine doesnt have a backplate, the bellhousing bolts directly to the block, so theres nothing i can remove to add more clearance.

I could cut everything away, but that means a LOT more fabrication. I dont have any TIG equipment, so i'll be tacking the plates to the housings with a MIG and getting someone else to weld them up properly. As such minimising the amount of reworking is a good thing, therefore i'd like to keep as much of the disco housing as possible so i can use the existing clutch slave housing and release bearing tunnel etc.

[DaveSIIA]

A bit of out of the box thinking - why not use a LT77 Defender bellhousing (shorter than the V8) and fabricate a back plate to fit the Audi engine?

You could position the Audi starter motor anywhere around the flywheel so that it doesn't foul engine bits, exhaust, etc or the clutch slave cylinder. Previous posts on this topic have pointed to the details posted by integerspin which give the bellhousing bolt patterns for the 4 cylinder and V8. The 4 cylinder pattern would match the Defender Tdi, and change the V8 to Audi. Thickness of the adapter to suit the clutch setup. Machine the adapter from a suitable thickness plate, or cast and machine. The clutch release arm and post for the pivot could be from a V8 LT77/R380 so that everything appears in the right place lengthwise. This would keep a good number of components standard for when they break!

BTW: My money would be on finding an Audi manual gearbox that mates to your engine and sorting out matching that to the LT230. R380's aren't the strongest of boxes.

[Aragorn]

well thats what i'm going to achieve cept i'd be making it out of a shortened disco v8 housing rather than the defender part.

The starter motor bolts to the engine itself, and i dont really fancy taking a grinder to the block to move it...

I was originally going to use the defender TDi housing that came with the box, as it wouldnt even have needed shortening, then just use the audi housing and some plate as an adaptor between the two, however it puts the clutch slave in the wrong place.

Audi manual boxes are all transaxles, so wouldnt really be suitable for this purpose, and i've been told by ashcroft that the R380 should be fine, although if it does die getting a newer "L" box would be a better bet.

[Night Train]

If the clutch and flywheel will fit inside the Audi housing could you make the cut and shut closer to the gearbox on the Disco housing and move your adaption plate far enough back so that you can still have clearance for the bolts?

ETA: Ahh, the Audi housing is already cut.

Could you include a tubed cut out in the adaptor and Disco housing to allow access to each of the bolts? More work but I think it will be more work what ever you do.

[Night Train]

My next thaughts were to use two pieces of alloy plate instead of one, with the two pieces doweled and bolted together before being welded to the bellhousings as before, this way i can unbolt the two halves, bolt the "flywheel housing" onto the engine first, then bolt the bellhousing part back on.

This may be the easiest solution if you can get the clearance for all the bolts.

I was originally going to use the defender TDi housing that came with the box, as it wouldnt even have needed shortening, then just use the audi housing and some plate as an adaptor between the two, however it puts the clutch slave in the wrong place.

Would it be an option to relocate the clutch? It might be an easier job overall.

[Aragorn]

The mounting points for the release bearing tunnel and the clutch pivot are cast into the housing, would be a pretty major job to cut them out and move them, hence me acuiring the V8 housing.

I think i'm going to attempt the two plates idea and see how it goes. I think if i make the alloy plates around 2-3cm larger than the diameter of the disco housing it will provide plenty room to bolt them together, and there isnt really anything in that area that will cause an obstruction with the flange that will be created.

[landmannnn]

A bit unhelpful at this stage but doesn't the audi v8 use the ZF 4HP24A? Take the front housing off and drop it on a RR spec ZF 4HP24 then it becomes a spanner only job.

A little knowlege is dangerous so I have probably got it wrong.

[Aragorn]

Your quite possibly right, it seems the earlier Audi V8 (my engines from an A8) uses the ZF 4HP24A, my engine would have used a ZF 5HP24A in its original application, but the bellhousing patterns are the same afaik...

However i dont want an auto box, i like my manual gears and Autos just dont press the right buttons for me.