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MG MGB Technical - 'Correct' steering rack, 73B?

My BGT is # GHD5 321152 G, said to be mid-1973. Everywhere I look up new (unfortunately all aftermarket) steering rack assemblies, I'm informed that the pinion shaft on the CB B until 1974 will be 44cms. Mine is 55cms, which seems to be "correct" for rubber bumper Bs. Has someone fitted a longer shaft in my case ( more trouble ... !), or was it common for mid/late 73 cars to maybe randomly be given a 55 cm shaft ?
When the shaft is only 44cms, what makes up the missing 11cm - just a longer universal joint?
All advice gratefully received.
John.
J P Hall

As far as I know the longer lower shaft was introduced when the V8 was first produced, so late 1973, and was applied to all models from the start of the rubber bumper cars. It was done because the UJ in the original position fouled the exhaust manifolds on the V8. To accommodate the longer shaft the UJ had to move back inside the cone on the bulkhead, and the UJ was made slimmer (but no longer) so it could sit partly inside the cone. Obviously the upper shaft needed to be correspondingly shorter.

I think that's right. No doubt if it's not someone will correct me!
Mike Howlett

That basically concurs with my information, Except that CB V8s had a unique rack, all RBs cars used the same rack. CB V8s also had a unique column, going by the part numbers.

An RB rack on a CB car will be a whole world of pain!
paulh4

Thanks - so if I order a new rack I need to specify that although it's a 1973 chrome bumper, it has the longer pinion shaft. There is nothing wrong with the shaft that I have - so as long as the gears on a replacement rack are cut to the same angle, depth etc I should be able to import my old pinion shaft if I have to.
Can anyone confirm that I should be able to do this?
Thanks all.
John.
J P Hall

Hang on a minute - Paul, in your website article you mention a 44cm measurement (on your vehicle I think) being from tip of splines at the u.j. end, to where the shaft enters the rack housing - if that is how it is measured, then mine is also 44cm!
I assumed the measurement quoted by retailers was the total length of the shaft, end to end. I'll ask a couple - but does anyone know what is correct?
John.
J P Hall

Useless piece of info for you----
Like you, a friend here had a 73 4cyl.MGB with the long pinion rack, It's interesting as the car has the non raised height crossmember so I'd imagine the rack is mounted in the normal early position, not slightly forward as the v8s are, so with the rack mounted there the universal would also be further back so must have a shorter column than the v8-------maybe
Then I found this------
Early v8's had a 2.9turns lock/lock rack ratio the same as early 4 cyl cars but with the long pinion and still had the large u joint
When R/bumper cars came out the gearing was changed to 3 1/2 turns for both 4 and 8 cylinder cars and both had the smaller u joint
Std B ratio from 62 to 76( introduction of smaller four spoke plastic steering wheel) is 2.9 turns lock to lock- this also includes factory V8s.
This means that the first two years of 1800 rubber bumber production shares its steering rack with the V8. CB std V8s usually have the continuous groove around the longer shaft in conjunction with the larger UJ. RB V8/1800 uses the smaller UJ in conjunction with the broad flat across the splines.
76 cars on use 3.5 turns lock to lock-long nose shaft with the broad flat groove.

Now the best bit I kept till last
A guy here had a chrome bumper V8 and wanted to lower it a bit and so replaced the front crossmember with a std early 4cyl one and it bolted straight in and everything lined up perfect

Little bit confusing all up

Does your car have the firewall corners at an angle like a v8 or straight like early cars
William Revit

Andrew at MGOC also refers to a measurement from top of uj splines, to point of entry into rack housing - so on that basis mine is 44cms, not the 55 I originally thought.
So sorry if I muddied the waters with my original question.
Willy, my steering column is certainly the standard '73 early version of collapsible ("semi collapsible" ), with the plastic sheer pegs. It's rebuilt and ready to go back on, when I either fix the non-existent bushing on my Argentinian steering rack, or find a replacement. They are akin to hens' teeth.
Thanks all for your input.
John.
J P Hall

Confusing indeed, although I'd have thought suppliers would quote the visible part of the shaft not it's overall length as they would have to guess the length of the 'hidden' part.

As far as the UJ goes the Parts Catalogue quotes AHH6000 for CB and 575732 for RB, for both 4-cylinder and V8. Looking at suppliers today pictures of the earlier type show the sealed unit I have on my RB V8 and not the type where you can replace the spider as on my CB roadster. However whereas my roadster UJ measure about 4.5" end to end, the V8 one is a good inch or so shorter, so I'm guessing current supply of the CB one has adopted the 'cost-reduced' technique of the RB one.

Whereas my CB roadster has the column shaft with a notch and the rack shaft with a groove all the way round for the UJ clamp bolts, the RB V8 has a notch in both.

One of the 'features' of the RB cars is that the rack shaft passes through the right-hand engine mount chassis bracket but not on CB cars - 4-cylinder at least. As all V8s had the round rubber mounts, did the CB V8 rack shaft pass though the chassis bracket as well or not?

You give two dates for the gearing change, Willy. According the Clausager the lower-ratio was only fitted to 1977 models and later.

I have a habit of typing 'bumber' as well.
paulh4

Both later CB and RB have shear pegs, but the outer of the earlier one seems to be a solid tube whereas the later is expanded mesh lower down covered with a plastic sheath. I had to repair mine, although with the ball-bearing at the top of the column hold that in place I doubt removal of the steering wheel using the hammer technique would have broken them as the same method on the CB roadster hasn't broken those.
paulh4

EDIT-
'And' I did say it was useless information---

Might have got myself confused there
3 1/2 turns from 76 onwards (Probably 77 model which would have been Sept76 on-?)when the plastic steering wheel was introduced meaning the first 2 years of RB cars 4 and 8 cyl had the 2.9 long shaft rack the same/similar to the CB V8's
With the last of the V8s built in Autumn 76 I doubt there are any, or very few V8s with the 3 1/2 rack

I still think John's best option is to make up a bush for the end of the rack he has already and give it a try, but that's on the other thread

willy
William Revit

Clausager again - last V8 and the start of 77 model year (and the modified rack) were both Jun 76. As he says elsewhere it's quite possible that due to availability of parts some 'new' parts may have been fitted before the recorded date "but as far as is known pairs of components were of the same type" ...

And yes, try and come up with a suitable bush.
paulh4

No information is useless, Willy - especially with your obvious depth of knowledge.
I am definitely going to try and rebush the original, irrespective of whether I order up a replacement. I have a son in seriously fast motor engineering who is keen to help me look at in when I'm in Townsville next week,
.Will add an update to the other thread, where I piggybacked a question from George and then kept going.
John.
J P Hall

This thread was discussed between 16/11/2020 and 18/11/2020

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