I have a defender 200tdi (disco engine) with a fully rebuilt Ashcroft lt77 gearbox and rebuilt 1.4 ratio transfer box in running 33s and averaging about 23mpg when on a run it feels like it needs another gear I have been told to put a disco transfer box on but as the ashcroft one has only been in 7 months I was a bit reluctant to swap it for a old disco one as I can't afford another from Ashcroft, would I notice much difference?
the_wolf
Well-Known Member
You would notice a difference but yours shouldn't feel like it needs another gear. What speed are you trying to do? The 1.4 is fine and I ran with it for many years until my box died and I replaced it with a 1.2 box from a disco. A lot quieter and cruised a lot better at motorway speeds so if youre after that then you could probably get a good bit of cash for your ashcroft box. I'm surprised you're only getting 23mpg though, that's bloody awful and 200tdi is supposed to be slightly more economical than the 300tdi (I disagree on this though, having run both my current 300 is definitely far better on fuel.)
Yeah when I mean another gear its just noisy on motorways etc and I do alot of traveling, I thought of buying a new Ashcroft 1.2 and then selling mine on as its still under warranty but I just wanted to make sure it's a good investment and modification
I think the poor mpg is down to tire size
I think the poor mpg is down to tire size
dag019
Well-Known Member
You should definitely be getting better mpg than that, I was getting about 27 on my 1.4 box with my 110 and a disco 200tdi.When I then put in a disco box I didn't change my mpg but I drove faster. I gained about 8mph for the same rpm in top gear which made motorway mileage more tolerable.
THEengineer
whatever
23??????? bloody hell i get 34 out of my 300 110,but its on standard 235
to find out what changing the transfer box ratio will do to your gearing just goto to the ashcroft website ratio calculator. Gives you all the options and tells you the RPM's at various MPH to see the difference.
With a 1.41 xfer box 5th gear @ 70mph is 2742rpm (33" tyre/3.54diff)
With a 1.22 xfer box 5th gear @ 70mph is 2376rpm (33" tyre/3.54diff)
Id worry that a 200tdi wouldn't have enough power with a 1.2 box.
With a 1.41 xfer box 5th gear @ 70mph is 2742rpm (33" tyre/3.54diff)
With a 1.22 xfer box 5th gear @ 70mph is 2376rpm (33" tyre/3.54diff)
Id worry that a 200tdi wouldn't have enough power with a 1.2 box.
no probs. other option is to fit different diff ratios (ring and pinion gears) front and rear instead of changing your gearbox. Obviously this will change both high and low ratios. Ashcroft do a variety of ratios for £195 an axle, and they are heavy duty etc.
Also, stating the obvious :lol: that if you get smaller tyres as recommended int this thread then it will be revving harder still for a given speed as the rolling circumference will be smaller.
Im currently working all this stuff out for myself for an upcoming v8 90 auto project, as in that case the autobox 1st is like an LT77 2nd which would ruin the crawling ability off road.
