[Zmagnette] 4 synchro MGB trans in ZB

Mike mikesmuseum at yahoo.com
Wed Nov 27 12:03:24 MST 2013

+1 to what SteveC said. Earlier this year I installed a HiGear kit in my MGA. It came with everything I needed, down to the oil for the gearbox, and it all fit. I had to drill four small holes in the driveshaft tunnel rails for the new transmission mount – that was the only modification. The kit even came with a right-angle gearbox for the speedometer drive, so I could use the MGA's speedo cable and leave the speedo's calibration alone.

According to HiGear's website, the Magnette kit is similar. The main difference is that they supply the MGA bellhousing, so you have to move the slave cylinder from the top to low on the right side, a la the MGA. The site had a note that if there was enough demand, they'd make a Magnette-specific bellhousing, but I doubt that will happen.

Regarding changing the axle gears, yes, this works, but IMHO a 3.9 gearset from an early MGB is too tall for a Magnette with its original 1500. Granted, I live in a hilly area (San Francisco), but the car was also slow to merge onto the freeways even on level ground. The car now carries a 4.3 from an MGA, which seems to be a much better compromise.

But when the Magnette's transmission wears out, I'm getting a 5-speed kit for it. No doubt about it. Well, once I've saved up – they aren't cheap.


On Wed, 11/27/13, Allen Bachelder <bachldrs at comcast.net> wrote:

 Subject: Re: [Zmagnette] 4 synchro MGB trans in ZB
 To: "List for the Z Magnette Group - North America" <zmagnette at autox.team.net>
 Date: Wednesday, November 27, 2013, 10:05 AM
As far as I know, the cheapest way to do this is with the Datsun 280Z five-speed (it has a "Z" in it!) and a Rivergate kit.  I've done it on two different Magnettes.  The kit is designed for an MGB so there is a bit of fabrication necessary - but it isn't rocket science.  The bit in question is the transmission mount. The Hi-Gear Ford Sierra kit is available from either Moss or Bruce Woodson and I understand there is a purpose-built version for the Magnette.

Having done the Datsun/Rivergate option, I can say that it is pretty darn easy.  The pictures show the only modifications done to the car.  Bear in mind that the PO had converted the car to the Datsun transmission with a kit homemade by his mechanic. The second picture shows how much material was removed from the back of the shifter opening.  In fact, this is more than necessary, but the third picture shows how I dealt with it.  I chose not to weld the new tunnel patch in case a future owner wants to reverse the conversion.  In this sense, in answer to frequent criticism, by using a Japanese transmission, I actually preserved more original MG than I would have with an MG transmission. Another advantage to this approach is that the old Magnette drive shaft still fits - requiring only that the front U-joint yoke be reamed slightly to fit the Datsun U-joint which of course has it's own front yoke and transmission spline.  

If I recall correctly, I used an early MGB shift-lever boot.   I did rework the flange of the shift-lever tower with a body hammer to fit its new location. The PO didn't use a tower at all.

One more thought.  If you're undecided about the transmission choice, first try replacing your original 4.55 differential gear set with a 4.3, a 4.1 (if you can find one), or a 3.9.  This is an easy two-hour job. You might find that even with the original gearbox, you're happy with the higher-geared rear end. It's interesting that the two ZAs I rode in while visiting the UK were both the earliest 4.87 rear-end types, and while we never went on the "M roads" with them (equivalent to our interstates), they seemed remarkably unstressed.  For awhile there, I started wondering why I had gone to all this effort.  But then I get on the I-69 here in Michigan with its 70 mph speed limit and I'm sure happy to have my 5th gear, along with the 3.9, giving me 25 mph per 1,000 rpm.

Allen & Florrie Bachelder       =iii=<
Spring Creek Home for Wayward MGs
'57 ZB, '65 B, '69 C/GT, '73 B/GT
North Street, MI 48049, USA

On Nov 27, 2013, at 12:42 AM, Steve C. wrote:

> As Steve K states I installed a 4 syncro overdrive many years ago in my ZA. I would not even consider doing so today. The 5 speed kits are so much easier to do. The come with everything you need and require almost no modifications to the car. To install the late over drive you need to build a rear transmission mount, a transmission tunnel, drive shaft, speedo gear box and cable. Then deal with the starter hitting the frame and making a clutch hydraulic line. I also did some mods to the shift tower, but do not remember exactly what. I think that covers it all.
> -- 
> Sent from my Android phone with mail.com Mail. Please excuse my brevity.
> Steve Kirby <skirby210 at cox.net> wrote:
>     It is not my place to answer this, and it is further not my place to offer up this answer, but I will anyway!  One of my first, of many, mentors, in the Magnette World was Steve Carroll . . . he of thee superb header set up many of us have purchased.  Steve did put a full late B synchro in his.  I do remember Steve describing the various things he had to do.  Steve is a person of immense talents, so his pay grade is much higher than mine.  Perhaps Steve will answer, now that I've prodded him a bit, or Charlie can contact him directly.
>     #2SteveK
>         ----- Original Message -----
>         From: LannM at aol.com
>         To: zmagnette at autox.team.net
>         Sent: Tuesday, November 26, 2013 8:29 AM
>         Subject: Re: [Zmagnette] 4 synchro MGB trans in ZB
>         Shifter location aside, the 4 sync is wider than the 3 sync.  Compare a 3 sync MGB with a 4 sync.  The transmission tunnel is noticeably different.  I've put a 4 sync in and early MGB and it takes a lot of work with a BIG hammer to move sheet metal around.  Even then, its still a tight fit.  I can't imagine a Magnette would be any easier.
>         I think Allen is right, a Hi-Gear 5 speed would be quicker, easier, and probably cheaper.
>         Lann 
>         In a message dated 11/26/2013 10:19:44 A.M. Central Standard Time, durningcharles at gmail.com writes:
>             Robert,
>             I didn't think that even modifying the remote would work.  It would still be too far back, not to mention the height.  I was thinking about eleminating the remote and mounting the shifter directly to the opening on the trans where the remote attaches.  I still have to get under the car and do some measuring to see if that would be close.
>             It would be good if some BMC car used the 4 synchro trans with a direct shifter.  That would keep me from having to make something.
>             Charlie Durning
>             On Tue, Nov 26, 2013 at 1:58 AM, <monster at caverock.net.nz> wrote:
>                 http://www.beardmorebros.co.uk/website%20pages/Dads_Oxford.html
>                 On the above page are some photos and a description of fitting an MGB engine and 4-synchro+overdrive 'box to a 1960's Farina Oxford.
>                 It includes a pic of shortening the remote gearlever extension to fit, and a new tunnel.
>                 I'd agree that the benefits of non-OD box over all the mods needed for a 3-synchro box might not be great.
>                 I also love the sound of the non-synchro 1st gear. Bah, musicians, eh? :-)
>                 regards,
>                 -- 
>                 Robert
>                 On 26.11.2013 15:50, Allen Bachelder wrote:
>                     Charlie,
>                     Even without overdrive, the remote shifter on the MGB 4-sync sits
>                     high and your going to have to substantially reshape the transmission
>                     tunnel to make it fit. That's a ferocious price to pay for a
>                     synchronized first gear. If you're going to that much trouble, you
>                     might as well go five-speed.

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