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MG MGB GT V8 Factory Originals Technical - Gearbox mounting

I am fitting a Rover R380 gearbox to my factory GTV8 and need some info on which mountings to fit. I have the original and an SD1 crossmember so I should be able to make something out of the two. Looks to me as if the crossmember will have to be moved further back by about 3 inches, will SD1 mountings fit or are they too high?. Also the remote assembly looks a bit long.
Any information will be much appreciated.

Mark
Mark Rawlins

Mark,

Use the RV8 as a guide and the first 650 or so cars had the LT77 (SD1 gearbox) whilst the rest of production used the R380 gearbox. The RV8 gearbox crossmember and all mountings remains the same for the whole production period. This indicates that what is applicable for the SD1 gearbox fit applies equally to the R380 fit.

In fitting the SD1 gearbox the common factor has been to either remove/modify/refit the original MGB crossmember or to replace the mounting towers with bought fabricated items. The main problem is as you say the different relative positions of the mounting positions and what you may bot realise, the wider spacing of the mounting hole centres. (about 3/4" wider on the SD1.)

As a minimum you will need the two 'cotton reel' type runbber mounts that have a single threaded pin either end. One end screws into the angled mounting position on the rear casing of the gearbox and the other engages into the tower on the crossmember.

Additionally you should add the third retaining mount which effectively bolts the tail of the gearbox down to the crossmember with a rubber insert to dampen noise and vibration.

The simplest solution, but not the cheapest is to use RV8 parts, although mounting rubbers are not expensive, only things like the crossmember are. If you want to look into the RV8 parts route then the following part numbers will help...
Crossmember ZKC 6605
Cotton reels CRC 454 (older Rover parts these)
Third mount (Bush steady) ZKC 6604
Bracket for above ZKC 6606

The SD1 remote, which is the same for the R380 (like many of the SD1 bits that fit the R380) will put the centre of the gear lever hole about an inch or so back from the centre of the hole where the gearlever comes through. ON the RV8 a cranked gear lever is used and I have created my own for my own car. This is not a major issue and is the simple and effective solution. Should you want to check out the RV8 price the l;ever part number is FTC 3631 for the LT77 and FTC 4238 for the R380. No I don't know the what the differences are.

Rog
Roger Parker

Roger
Thanks for the details. I have found some cotton reel type bushes and the centre steady I have adapted the MG's.
When I offered the gearbox up to the engine it was apparent that the shaft that goes through the clutch and into the crank is approx 4.5 inches too long. I bought the gearbox secondhand although It doesn't seem to have been used. It is definately an R380. Have you any Ideas. Is there another shaft available and more important is the gearing going to be OK. The gearbox number is 55A 0282060J. I was told that it was for a Morgan/Marcos and as the old Marcos factory is in my town I thought it credible.
Could you possibly put me in touch with someone in the know.

Thanks

Mark
Mark Rawlins

Mark

I dont have experience with the R380 box but I am working on the assumption that the mounts are in the same postion as the LT77 mounts.

I found that the V8 conversion co mounts didn't work for me-the drawings in R Williams book do not make sense in practice. You also want to consider the gearbox height-if you are insatlling the box into a std factory V8 you will probably have to modify the top of the tunnel to accomodate the taller 5-speed box.

Height considerations aside-my solution was to use the MG x member-I cut the gearbox mountings away completely and installed the x memeber so that the front x member holes were bolted to the rearward captive nuts in the chassis rail. this puts the x member directly under the gearbox mounts if you are using factory engine mounts. You then have to remove the seats and cut open the floor pan above the chassis rail to install a captive nut plate in each of the chassis rails for the rearward x member bolts.

I then used the std SD1 x member welded to the top of the MG X member -as I recall the flages were about 10-12 mm apart- the distance is determined by propshaft angle,bellhousing flange clearance,clearance to the top of the box/tunnel. I used a series of 3mm thick vertical plates shaped to the inside profiles of the SD1 and MG members to create one strong x member. You also get the advantage of engine restraint from the vertical bolt going through the SD1 member.

I think that you need to consider the height problems first- I think that you will find that body mods are neccessary.

Regards

John Bourke
John Bourke

John
Ive been busy with a grinder today chopping a hole in the top of the transmision tunnel. All I need now is to get my R380 to fit the engine then Im ready for a trial fit. What propshaft mods do I need to consider?

Cheers

Mark.
Mark Rawlins

Mark,

David Vale at V8 Conversions in Farnborough in Kent used to supply a propshaft (possibly on exchange, if my memory serves me correctly), that fitted the SD1 box at one end and a B diff flange at the other.

When I say 'used to', this was in 1994/5 when I converted my B. I'd give him a ring - he's an extremely helpful chap.
David Daw

This thread was discussed between 30/11/2000 and 04/12/2000

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