3.54 diffs and an Ashcroft transfer box - silly idea?

Hi all
Wondering if anyone has views on fitting 3.53 diffs to a 109 series that already has an Ashcroft high ratio transfer box fitted to a 3.5v8. I’m planning a super long road trip / expedition and want to be able to cruise at 65 easily for long periods of time. Although the Landy is great for short motorway trips it still gets pretty hard work for longer stints so am thinking of all options.
Thanks
Alex

I am thinking similarly since my 109 is 200tdi powered. The 4.7:1 axles are a bit overkill.

Here is a post i found about this very thing: https://www.landyzone.co.uk/land-rover/which-diff-to-upgrade-to.390595/post-5656209

I must have had this idea 10 years ago when I got the 109 because I found a box in my garage from East Coast Gear Supply with a:
Dana 60 Slasbury 3.54 ring, pinion, 3-series case, and an overhaul kit. At the time I didn't really get how these transfer cases worked (i had been lead astray)

So these are the right parts for the rear if i am to trust my younger self to have researched it. Would the front be the same?

atkinsal said:

Hi all
Wondering if anyone has views on fitting 3.53 diffs to a 109 series that already has an Ashcroft high ratio transfer box fitted to a 3.5v8. I’m planning a super long road trip / expedition and want to be able to cruise at 65 easily for long periods of time. Although the Landy is great for short motorway trips it still gets pretty hard work for longer stints so am thinking of all options.
Thanks
Alex

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Has to depend on many things. The V8 often sounds like it is revving hard when it isn't. You'd run a 4 pot at the same revs for instance.

It is very easy to over gear a vehicle. And how fast do you want to go?

I had a 200Tdi S3 88, I did put 3.54 diffs in, but had the standard transfer box. It did improve cruising. But it also sort of ruined the vehicle IMO. It made 1st gear quite tall to pull away, which you noticed if you were towing. It also impacted low 1st crawl speed off road. But for me, the biggest issue was the gap it produced between 3rd & 4th. As in, 3rd at 30mph felt like too many revs, but it no longer wanted to pull 4th really. Not unless it was flat level ground. However, the different Series boxes do have different 3rd gears, so might not be an issue for you. Mine was a Series 3 box.

Don't get me wrong, it wasn't terrible at all. But my plan, had I kept the vehicle was to return to 4.7 diffs and fit an overdrive to the gearbox.

The good thing is, swapping diffs isn't the most amount of work or money. So it is easy to try and out and reverse if you don't get on with it. Ultimately, I suspect the only real way to know is to give it a try and see.

Looking at the calculator your current setup should be approx 2600rpm @ 60mph, which doesn't sound too bad to me.



3.54 diffs would drop 60mph in 4th down to jut below 2000rpm. But I'd wonder how usable 4th gear might be below 50mph, at it would all be sub 1500rpm. And mot low CR 3.5's are not all that grunty really.

@300bhp/ton seems I was right to quote you above. Would you mind weighing in on the proper parts, particularly for the front. IIn my case i am jsut making a leafsping defender with a cooler front end. Would it be easier/cheaper to just swap the entire axle and get rid of the unused locking hubs?

wrickm said:

@300bhp/ton seems I was right to quote you above. Would you mind weighing in on the proper parts, particularly for the front. IIn my case i am jsut making a leafsping defender with a cooler front end. Would it be easier/cheaper to just swap the entire axle and get rid of the unused locking hubs?

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I didn't have locking hubs on mine. Mostly they are aftermarket and often prone to issues or leaking. I never felt as if I needed them. In theory they can offer mpg benefits, but I didn't own the vehicle for mpg.

As for what parts. What are you trying to achieve?

There are lots and lots of options. Leaf sprung is cool and can be made to perform well. This is my build thread: https://www.landyzone.co.uk/land-rover/200tdi-s3-88-pas-long-travel-suspension-rebuild.298104/

Sad to see it go.

Something people sometimes do here in the UK is fit coil sprung axles as they are wider, come with disc brakes, 3.54 diffs and are generally stronger out of the box. A Discovery 1 is good candidate for some axles. You'll need to add some spring perches and like to retain leaf springs. But quite doable with a welder, grinder and some metal plate.

Other options are to go for full coil suspension. You can either chop down a Discovery/Range Rover chassis and put the Series/Defender body on it. Or you can fab up all the mounting points.

My current project vehicle is an 88 coiler with modified Tdi engine.



This is another coiler 88 in the USA, very interesting build series, keeping the original chassis and using some Toyota bits:

@300bhp/ton my inclination is to keep leafs and eventually upgrade to parabolic springs and the appropriate shocks. I keep an open mind in case something just comes along that is clearly better.

For parts, I just want to make sure I get what I need to convert the front differential to 3.54:1. I seem to recall the front and rears being different. I have a full rebuild for the rear (pictured), but before I go searching/ordering a gear set I want to make sure