Thread: Diff ratio for 33"

my money says 4.1:1

I ran standard ratios for ages on 33's with my 300tdi auto, it handled fine. The speedo was waaaay out tho, have to be aware of that. 92kmh on the speedo was 100kmh real speed.

Have since changed to 4.1's., brings gearing back to normal, if not a little higher. Now speedo 100kmh = 93 real, so you can see how much the diff ratios changed the gearing.

Thanks guys.

If i do change gearing do i have to change the rubber roto cuplink to a solid uni for the back?

And what will i have to get to change this?

4.11 or defender high range transfer case gears.

to just change the diff ratio no..

HOWEVER...

Im tipping that if you're running 33's that you also have a suspension lift of the +2 inch or more variety, Based on that, yes you should as the coupling will wear out faster but its not mandatory.

All you need is the shaft/flange assembly out of an earlier disco thats got the solid unis all the way through

I'd also look for 4.11 rather than 4.1 diff gears. They are different tooth counts and the 4.11s are stronger. I also belive that someone (Ashcroft???) has a 4.13 which is stronger again, but I suspect you will get more diff noise with them.

The rotoflex rubber couplings are good because they absorb shock when you do silly stuff - as you will. They will definately fail, but I haven't seen one break apart, justs collapse. When you change to a uni joint it will be a strong setup, but you may get vibrations and your axles and diff will then take up a lot more of the shock loading.

I am running 4.11 Ashcrofts in my D1 Tdi.
I have ran 33's, and now run 35's.
I am happy with the reduction, and works very well !!!

New ashcroft ratio is 4.12.. go with this. The Tdi shouldnt have come out with 3.54 IMHO anyway.