Thread: 51 MG restoration.

If it is a banjo diff, it's really old-school. Only one I ever did was on my Model A. Went from 4:11 to 3:54. Not much gear selection in those oldies.
Bought a book and took my time. Stacking paper gaskets to get preload. Swapping them from side to side to get a good pattern.
Pinion preload and depth was done same. Was crazy.

Anything 'modern' out there you might put under that? Banjo style diffs are not made for high speed I think.
Jeep Dana 35 might have a big selection of ratios? Lots take those out to put heavier duty ones in for off-roading. 3:07/3:08 is possible.

https://en.wikipedia.org/wiki/Dana_35

Yessir, Hardy Spicer Banjo style diff. Was used right up into the mgb’s before they switched. Mine was out of a Magnatte, but the gears were from an MGA. Figure I’m 4.55:1 which was stock mga gearing, on a 1600cc car.
Mine @ 2100 cc and the upgrades, should easily run 3.7:1 all day.
Haven’t found a more modern upgrade online yet, and used ring snd pinions are not as plentiful as I would have expected being one of the strongest components in the entire build, traditionally. They normally never fail.
Terms like ‘the pumkpin’ are not familiar to me, but I did find a few tear down walk throughs online.
Seems these do come out of the diff quite easily leaving the axle In place for the swap out.
Shims and backlash being critical I feel if I go this route, a bunch of shims will be needed to ensure a quiet set up.
Thanks for the suggestions Tom, really appreciate your experience.

3:7 is a long way from 4:55. That's for certain.

A banjo diff is often mis-identified. Once you get the axle housings off, it looks like a ginormous banjo fitting!
Here....


If the whole diff pulls out from the front, you have a removable carrier.
Like this...



Cover on the back? Integral carrier.

Don't mess with used gears, Mike. Get someone good to set them up is my advice.

Ahhh. Mine is like the second image and as I look they call it a banjo style not banjo and thanks to the pic you provide now I get the name as mine doesn’t look like no banjo I ever heard.
Moss has new 3.7 or 3.9 to 1 gear sets for the hardy spicer diff and both are the same price so really it comes down to expected torque curves.
Not in my wheel house calculating how much faster road speed wise one is going to be over the other but I wish there was.
Going to hold off on any speedometer adjustments till all this is figured out.
And part of the rationale behind going 3.7 is that is what the stock tr4 is married to, gearing wise. I figure the engine now is effectively a bumped up tr4, and people running that displacement are running with 3.44:1 gearing from my new research so I should be in a comfortable zone at 3.7 even though it is a big jump from the current 4.55.
Look at the ridiculously low hp, and displacement these things were coupled to originally.

Hay Mike! Thought of you when I put this junk back on the car!

Aww shucks bro thanks.

And Ness said I went with a crazy paint scheme, hehe.
But that looks da bomb Tom!
Presume you taped off the timing marks, or they show through the paint?

Who can see timing marks with all this hoo-haa aftermarket serpentine stuff?



That's all out the window anyway. Timing by seat of the pants from here.

It's Hemi orange. That or a blue or a green. Chrysler colors. Camera fogs instantly it's SO humid out there...

Holy crap, I did not expect to see all that on the front of those two coolant ports, lol!
Such a beauty power plant those American 8s are! Or were I should say.

Humid night? Sorry buddy, and up here there is a cooler night after couple days of heavy rain..

Gear Ratio Calculator

The above is a cool calculator for all things gear ratio related.
Punch in your transmission specs, and rear end etc, spits out ratios and speeds.
This screen shot shows my original 4 spd coupled to those new 3.7 gears on the left, and the 5 spd I’m looking at with my current 4.55gearing in the right.
Speed is shown in km’s, as that’s what I’m used to up here.

Interesting in that I can get damn close to what my speedo is putting out with just the diff gears and more than enough for hiway cruising as well..
So based on the above, and availability of parts, time and cost, I’m now thinking maybe the diff gears now, and keep an eye out for a 5 spd local, cause patience could be the key to finding these more obscure items.
Cheers gents.

Well, think on it good. I have seeen so many make gearing mistakes . If you are taking off in 2nd with plenty power, you are way off.
gearing it right would be like installing another gear? Also, look at the spread in trans gear ratios. If they are widely spaced, your power might suffer by going lower.

Usually the 1st gear to second is the widest spaced. It sucks to have good low and a bogging bomb when going to 2nd. A lot depends on the torque the motor makes when at a certain load/rpm is reached. Lots of variables.

I figure the ratios are pretty close in a 4 cyl sports car. I have had 2 Miatas and it's shiftorama constantly to keep it pulling. 5 speeds with the upper 4 close will keep you busy! Keeping it in it's power band is crucial.

My Tiger has a wide ratio 4 speed but it has insane torque for a small car. The factory 2:88 is perfect to me. I can go around in the neighborhood and never get into 4th.
It will enable ample acceleration to slow, make a turn, and then power back up without downshifting. I only stay in 1st for 10-15 seconds at most.
Nice for the highway. Speeding up after slowing requires no downshift.

Don't make a dog out of it but remember your goal.

It takes math and lots of info on your motor/trans/weight, etc to get close. Above my paygrade.
In light of what you typed above, the 3:44's might be best? You are bound to be lighter than a TR4. Or not?

I would google and read a lot.