Anyone heard of reversed gearbox fitted behind normal gearbox?

OK so I'll start with the background story of my day.
3 things happened:
Firstly, and unrelated, my truck went in and passed rego inspection, YAY!
Secondly, while driving back home on an old piece of now bypassed highway, I slowed down to what sounded like a reasonable amount of revs for cruising. So after getting a nice casual note out of the old girl (345 V8) I then looked down at the speedo and it read 60kmh!
I thought Jee Wizz I should be doing 90kmh at this revs! And realised that it would mean stepping the diff ratio all the way from 6.2:1 to say 4.11:1!!!!!!
Yeah sure it's probly 2 gears too tall for normal loaded driving but I don't care.
Ok third event for the day:
I went to look at a spares truck that I was told was an Acco 1830b with low km dot4 turbo, T253, eaton no4 with "taller than standard" ratio.
So check it out and it's a 1830a which seemed initially good coz I could maybe use the hydraulic braked diff as a straight swap for mine rather than the later model with air brakes. However a quick look at the ID plate revealed the housing was a Rockwell two speed of 6.5 and about 8 point something ratios.
I then jacked up one side of the axle and marked the tyres and tail shaft and checked the splitter which was already in high so I spun the tyre and got almost exactly 3 tailshaft turns to one wheel revolution which meant the centre had only been swapped up to 6.1 from 6.5. Barely worth it if say.
The cab was so rusty that you could almost gain access through the holes in the roof!
The exhaust stack had rusted away at the first bend and was now non existent and last rego was 1998 so I had to wonder if the engine was fit for anything or if it had seized from water ingestion or just due to not being started in up to 20 years.
For a seemingly bargain ticketed price of $1000 I walked away disappointed and very deterred away from even making an offer due to the only thing of value being the motor had a very unquantifiable condition.
I drove home regrouping my thoughts and was primarily concerned with my eagerness to still significantly change my final drive ratio above anything else like sourcing a diesel.
Thoughts of super tall late model diffs and double overdrive road Rangers and adding Joey boxes entered my head and the cost of them all to set up in my truck.
Then I remembered an old bloke from my days at tech years ago that said he once new a guy who had a Holden one tonner with a super slow diff who wanted nice slow revs at 100kmh so behind his 4 speed he rigged up a BACKWARDS facing Holden 3 speed in a Joey box style situation therefore giving 1:1 in top gear of the back box and 2 overdrives of very large steps when using the other two gears.
Has anyone heard of such a thing in trucks? Having never seen it done first hand Id have questions about how to connect the backwards facing input shaft to the tailshaft and also I wonder about whether the strength of the input shaft is the same as a normal output shaft.
If this concept were remotely possible and if so, executed using a 5speed direct box for closely stepped overdrive steps, it would be just the thing I'm looking for to take ratios from normal into the well and truly too tall to pull category
Hopefully someone knows of someone who has done this!
Sorry for the novel!

It is possible to use 2sp joey box back to front,and is sometimes done in restored 190s,effectively halves your revs.Ill tell you a sad story of a man who talked endlessly of diesel engines ,gear ratios,grade climbing ability,road speed,fuel economy in the days when it was 3/6d a gallon.He was my old man,and he drove a petrol inter to the day he died.

6.5/8.86 are #4 Eaton ratios.Were you looking at an Eaton centre in a Rockwell housing?None of the big 2sp D/R Rockwells have a 6.5 ratio.I mentioned some time ago that Rockwell dumped their own 2sp diff,and used Eaton centres in their housing.Which is what a 1830 should have.Offer the guy $500 for scrap,take what you want,and scrap the rest.

Yeah the name plate on the housing pretty sure was a Rockwell. Looked much the same as my Rockwell nameplate and the centre resembled the other 2 speed rockwells I've seen.
I'm not sure if you can source replacement gears for these any more.
Can you explain reversing the Joey box? I thought they had low, direct and overdrive and I assumed they would've had the same step between each.

Shaun most joey boxes I have seen are direct and then under driven 1 - 4 speeds
Providing it has no oil pumps driven off the shafts you can put them in the other way round

I see your a Leyland tractor bloke now thats something a bit different these days I had a 285 up until we shifted north 10 years ago and have spent many hours driving some different smaller ones


Paul

The Leyland 245 beats a MF135 hands down even tho they run the same 3 cylinder Perkins. The 245 is a heavier tractor and can take bigger tyres.
Very easy to work on.
My 285 is opened up full on the pump. Pulls like a train driving a 7ft slasher

If anyone has a Joey box laying around I'd love to see pics of the front and back of it. Do they have a 4 bolt flange on both ends like the back of a normal box?
Sounds like the 4 speeds are like a T17 with a different front.
Also which trucks did they come off? Did different trucks have different versions of the Joey or is it pot luck until you check it yourself?

I'll get under and take some photos of mine, it has about a 3 foot jackshaft from the back of the main box to the front of the joey.

Second try

Mmm nice! How many gears under or over?

Hi FarmerShaun I have just travelled half way across SA to get an overdrive gearbox to speed up an AR 160. The box comes out of an AACO with a Perkins motor in it. Once i got it out the bellhousing looks a lot different and I have my doubts as to whether I will be able to adapt it to my truck. If I cannot fit it you might be able to use it...it is .8 in overdrive 5th gear. will know in a week or so. Are you in SA