If you have the original 66 engine, you will need a later (68 ->) starter,
flywheel, and engine back plate. The 66 engine would be a 18GB. If yours
has had an earlier engine put in (18G, 18GA), stop now. The crank is
different.
BUT... I just learned about a week ago that there is now a kit to
adapt old cranks to new transmissions. The issue is the size of
the pilot bushing in the crankshaft; old engines expected a smaller
input shaft on the transmission. Call O'Connor Classics if you're
interested; let's see... (408) 727-0430. They're in Santa Clara
and will probably ship (now I've forgotten where Eben's original
request came from...)
> - Finally, will I have a problem fitting it in my -66 trans tunnel?
Yes. The shifter comes out in a different spot, and the trans may not clear
the top-right side of the tunnel. Also, the shift lever *is* different,
I've installed a '72 engine and transmission in a '65 chassis. In my case
I was lucky and a previous owner had done the right-side tunnel mods, so I
can't talk about them except to say that the floor of a '67 and earlier
car is of a different shape than of a post-'68 car. Look at the carpets
or mats if you want to see.
The shift lever comes out about 2" farther back than on the 3-synchro box.
I cut a crescent about 3" wide and 2" deep at its fattest point out of
the trans tunnel and the shift lever fit perfectly. (This was in a race
car that had already been fairly heavily sliced and diced when I bought
it, so you purists can put down your blood pressure medication... :-)
I also had to fabricate a little extension to the trans tunnel cover on
the '65 chassis, using sheet aluminum and fiberglass. It'll look really
nice if I ever finish it...
and you may need a different driveshaft. (measure total unit length,
bellhousing to output flange). Hmmm, at the same time BL changed the
trans to four syncro, they also changed the rear end.
Ummm, ALMOST at the same time. The later rear end shows up as early
as 1965 in GTs and some roadsters, while the new transmission doesn't
come into use till the 1968 model year. If the donor car was a '67 GT,
for instance, it'll have a three-synchro box and a late rear end.
I'm not at all sure on the driveshaft,
or even on how to check it, short of "install and see".
Well, you could do what Danny and I did and measure the distance... :-)
Here's the scoop on MGB driveshafts.
MG made (discounting O/D boxes) two transmissions and two differentials.
The early gearbox (as mentioned above) was a three-synchro box; the later
is a four-synchro box that is slightly longer.
The differentials are also different; early differentials are slightly
longer (or rather, come slightly farther forward) than the later ones.
Here's where it gets sticky. Your '66 B could have either an early or
a late diff in it; all GTs got the later, tube-type axle, but roadsters
from '65 through '67 were made with *either* the tube-type or the early
banjo-type axle, depending apparently on which ones they happened to
have in the shop that week. No, really.
How to tell them apart: Well, you already know you've got a '77-80 trans.
The diffs are easy. Are the bolts that hold the diff into the axle housing
located on the FRONT or the REAR of the center section? If they're on the
FRONT, you have an early (or banjo-style) axle. If they're on the REAR,
you have a later (or tube-style) axle.
This means there are four possible trans-diff combinations:
- If you're putting an EARLY transmission with an EARLY diff, no problem,
just order a driveshaft from a '62-'67 MGB. This isn't the case, though,
for Eben with his '77-80 box.
- If you're putting an EARLY transmission with a LATE diff, you're okay.
Order a driveshaft from a '65-'67 MGB-GT. This isn't Eben's case either.
Eben's condition is one of the following:
- If you're putting a LATE transmission with a LATE diff, you're in fat
city. Just order a driveshaft from a 1968-up MGB without O/D and
bolt it in.
- If you're putting a LATE transmission with an EARLY diff, you get to
do what Danny and I did, but with the added benefit of learning from
our mistakes. Basically, the factory never supported this combination
and all factory driveshafts are probably too long for this.
Here's the procedure.
1. Measure the distance between the gearbox output flange and the
differential input flange. It'll be something like, oh, 27 1/2 inches
(Warning! Imaginary number alert! Do not use this figure!)
2. Take your driveshaft to the local Driveline Services outfit in
your city (look them up in the Jello Pages).
3. Tell the nice man behind the counter that you want your driveshaft
shortened to fit a 27 1/2 inch (remember, I made that number up; use
your own tape measure, please) distance from transmission to diff.
4. Come back, pay about $40, and get a nicely shortened, welded,
balanced, tested, and painted driveshaft to put in your car.
If you need to have the U-joints replaced, it'll cost a little
more, but if you get the driveshaft from a breaker's yard, it's
probably a good idea to have them at least inspect the U-joints.
What we did was a little more complicated. I measured the distance of
the slip on the driveshaft's yoke, divided that in half, and then measured
how much of the driveshaft we wanted to remove in order to center the yoke
when the car was at rest. The DLS guy said that normally, all you do is
tell them what the distance was between the diff and transmission and they
will calculate the amount of required slip for you.
|