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MG MGB Technical - Salisbury diff ratios

Hi All.
Can anybody advise the different diff ratios I can get for the Salisbury axle in my B. I want to build hill a climb car and think I need something lower than a 3.9. Does the Land rover 4.7 fit.
Thanks
s page

Your diff ratio is best left till you get it going and decide then what suits you and the hill
4.7 will go----what model is your B
William Revit

Hi William. 1978 GT. I am intending to shed as much weight as possible but are not intending to not tune the motor the first year.
s page

Simon

If you’re looking at shedding weight, change the rear axle for the lighter banjo version. You can then change the diff ratio more easily.
Dave O'Neill 2

Hi Dave.
Happy NewYear.
Have you seen the price of banjos? I have to stick to the original axle.I am just not sure what ratios are out there. I was wondering about LDV, FreightRover or Sherpa. It seems Landie 4.7 might fit but I was hoping for something between 3.9 and 4.7, and that doesnt cost the earth.
s page

78GT should be a straight forward conversion Finished yet--?
My bet is you'll end up going the other way with the axle
I've had that many different ratios in my V8s over the years that it's not funny
Depends on your hill really
To me 3.9 is about the limit for a decent v8
All the gears are too spinny otherwise and while you're sitting there revving away changing gears the taller geared guys are way up the road/hill
Around 3.2--3.3 is about as spinny as you want to go to get any speed generation, 3.5 gets into the going nowhere zone as well-
around 3:1 gets some serious speed off the line but as said before it depends on the hill and the ability of the driver
Just to give you an idea, with a 3.9 and a slightly worked engine, jumping on the throttle at 60kph in 4th gear, it'll break into wheelspin
I've found a 3.23 to be a good all round performance ratio ,it gets off the line well and has a decent speed generating feel to it,but again it just depends on the hill, the car, and you

The crownwheel carrier in banjos don't hack the power of v8s very well

Main thing---------------have fun--be safe
William Revit

It's a lot of work to change the ratio on a Salisbury axle, if you can get the alternative ratios. As Dave says, the banjo is easier, but they're getting like expensive hens teeth.

I competed at a pretty low level in my '72 Roadster with the standard 3.9 diff in sprints and hill climbs in the South West eg Prescott, Wiscombe, Gurston Down etc. The axle ratio was the least of the issues!

You're on the right lines with thinking about weight loss. Binning those rubber bumpers for a kick off depending on the class you're competing in. At the time I was doing it I was absolutely skint, but even with a fairly standard car still had a lot of fun and wasn't the slowest against a cross section of sports cars of the time.

If I was doing it now I'd say as you've a rubber bumper car start by lowering it. Then stiffer front shocks, front anti roll bar and decent tyres. Making sure everything works as it should. Sky's the limit with the engine, but initially ensure engine is set up to the book. When you're flush and got into the groove a PB head and a rolling road session would be useful.
Peter Allen

Peter,Simon's going v8
A banjo is useless in a v8
i can send you a heap of bent c/w carriers if you need proof, and there isn't a ratio any taller than 3.9
Cheers
willy
William Revit

Thanks, Willy, stand corrected! Using a 3.9 Salisbury axle makes even more sense then as they're relatively cheap, fairly strong, and a little lower (back to all that cwp high/low thing!) than the V8 3.7.
Peter Allen

Willy

I didn't see V8 mentioned anywhere
Dave O'Neill 2

Hi Guys.
It certainly wont be a V8 this decade, but one can always dream. If I was going to any big changes it would be a super charger. I had just hope lowering the diff to something like 4.3 :1 would help acceleration.
s page

Not having seen the price of banjos, I'm intrigued as to how much they are.
Getting the gearing right can have more influence on times than an expensive set of engine mods, so its worth looking at in that light.
Willy, I know what you mean about the banjo limitations. I run a 4.875 in conjunction with the close ratio box to bring 1st gear back to realistic levels (overall still some 12% higher than std) and find that long rallies with a lot of 1st and 2nd work on twisty stages end up spreading the housing.
Paul Walbran

Dave/Peter / Simon---my humble apologies
When I read your first post I misread it as that you were fitting a LandRover 4.7 engine
I am currently crawling back in my hole-----
SORRY

For what it's worth,now that you're 4cyl. depending on the class rules, I'd go Escort banjo axle, there are heaps of ratios from 5:1 through to 3.7:1 and lots of optional centres / axles etc available for further upgrades - limited slips ,lockers anything is available for them
I have a friend with a RS1800 with around 220 hp driving through one and never has an issue

By the way, have any of you seen the new Quaife semi helical gearsets for the T9, and you can choose ratios for 1st and 5th
Got one with 2.23st and .82 5th for the Escort----good looking set of gears to replace the growly old s/c set

Again Dave/Peter -sorry for the mixup there
I just get excited when someone talks about going fast
willy
William Revit

No probs, Willy! If there are cost considerations with an MGB banjo, there certainly will be with anything sporty rwd Escort. For some strange reason, old Ford and Ford parts values in Blighty have gone ballistic in the last few years. And that's before you get to engineering considerations. I still maintain that the standard diff in a fairly standard car is good enough. You're out of first straight off. However, there maybe an argument for addressing the gap between 2nd and 3rd which I always found a bit of a frustration, but I don't think this would be solved with an axle change.
Peter Allen

Cheers Peter--to be honest I'm feeling a bit stupid for my mistake on the engine,but it is what it is

Probably back to basics and Simon probably needs to run his car first to see what he needs gearing wise, the gearbox could well have a perfect ratio matched to a std axle ratio to do what he wants or close to it which can be adjusted with tyre choice
No use spending heaps on something that's already fine as is
William Revit

13 years ago I could have sold my Ford Capri diff for more than I sold the whole car for as it was wanted for Escort sports. Glad to say the Capri went to an enthusiast who totally restored and used it as a daily and show car putting on 90,000 miles of use since and remaining in show condition (something it never was in my short ownership).

Like many fashionable (or enthusiasts?) classics prices and costs have gone very high on Ford Escorts in this country.
Nigel Atkins

This thread was discussed between 07/01/2020 and 09/01/2020

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