OLD M.A.N TRUCKS

All

I was looking at an old MAN diff just the other day. I didnt actually look for a ratio or bother to count teeth - but at a rough look - it may have been close to a 1:1 ratio. The pinion was as big (or bigger) than the crown wheel.

It was just a 'center' so have no idea as to what the hub reduction (final ratio) may have been.

My point being - the diff ratio (crown & pinion bit) doesnt compare with most convential diffs, and the 'reduction factor' is in/at the hub reduction end.

And I'm told - the 'centre' bit were all the same ratio - with the overall ratio variance obtained via options with the hub reduction ratio.

The owner of this piece apparently discovered they were all the same when he ordered the one I saw - supposedly getting a faster one for his truck. Only to find it was the same as the one he already had, and what he really needed was different hub reduction gears.

Not sure how this might help anyone - but sure seems like whats being discussed here!!!!

Oldfulla

Does anyone have a pic of the old MAN factory at Kurri Kurri NSW?

What I was getting at is that you have a hub reduction type diff centre in a non hub reduction axle. Alternately the hubs are locked and not reducing. Fodens had an arrangement where you could lock the diffs for road work and unlock them for deep reduction.

Hi All,

This one on Gumtree at the moment looks like Stephen's "Chubby Cheeks", but tandem drive.
www.gumtree.com.au/s-ad/mannum/heavy-far...-off-road/1030485242

Regards
Roger

Busntruck no photo of the kurri kurri factory but 1972/3 I had a few loads into it from Sydney, the bloke I worked for, Des Foster 407 Princes Hwy, St Peters had the contract to clear the dock when the MAN bits arrived into Sydney docks, Darling harbour Pyrmont and Walsh bay, you had 3 days to clear the dock before storage charges were imposed. The parts were all boxed, engines, gearboxes, axles even fully trimmed cabs in huge crates, chassis were bolted together in packs of about 4 or 5 I think and wheels were bolted together, up the Pacific hwy to Doyalson the off to kurri, up at night back and load for the next night, I only had a few trips, using bonnetted man, s with pogo stick gearboxes.

All
These photos are of the later model MAN diff.

I suspect

Pete I use the dummies method>
27 turns of the propshaft=18 turns of the axle.
Then divide the 18 by the hub reduction(3.48) gives approx 5.17 turns.
If 27 prop turns = 5.17 wheel turns
Then "X" prop turns = 1 wheel turn
"X" comes out at 5.22:1 the total reduction.
She's a more modern diff to the one we were talking about with the load axle and the separate diff with half shafts to bull gear assemblies.

Pete, you've got a little typo in there too mate, 4.11@2100 is 60 MPH, and the old Road Train ratio was 5.29 which was 50 MPH @ 2100.

That MAN diff looks like it could have come out of a bus with the underslung suspension.

Hi Cam,

I was thinking the same thing re: the bus type diff. It is very similar to the diff "we" pulled out of a Mercedes Benz bus.

Jeffo, BigCam & all

Jeffo - it makes a huge difference if one knows which is the pinion and which is the crown wheel. Even after my making the NOTE (in the story) of the 24 teeth pinion on the one in the photo.

And yes - a bus diff - and much later model than is in Chubby Cheeks. It will have the bull gear type ruduction -with the diff centre sitting (above centre) - in space above the load carrying dead axle.

BUT - my memory of those old ones - is the diff center (when viewed from behind) was distinctly rectanguler shaped (like in the photo). Hence my comparison above.

Cam - good pick up on the 4.11. I just wish it was a typo on my part - not the memory lapse it really was!!! Sort of stuffs my 2.88 theory too??

And the photos of the full rear end is out of a bus. And not a very fast one either. The reason it is laying where it is - is because it would only do about 90KPH (like the ratio suggests), and has been replaced.

Oldfulla