Vehicle & Technical > Defender

Diff ratios

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Jimbo:
I'm trying to figure out why my 110 Td5 won't go much over 65-70mph, it's running on BFG muds 265/75/16's and we believe has a standard transfer box (43D******G).

Dave Ashcroft is certain that the t-box is the standard 1.410 ratio - but without stripping it apart, there's no way of telling whether the 'innards' have been swapped for different ratios.

On the Ashcrofts site there's a formula for working out your MPH per 1000rpm - but you need to know the diff ratio.

I've tried a couple of numbers (4.7, 4.11 and 3.54), but these all give bizarre results - with 4.7 in the equation, I get a figure of 57MPH per 1000rpm..........so in theory I should be doing over a ton at 2000rpm  :shock:

Anyone know what ratio my diff should be - just realised, the formula doesn't say front or rear diff  :?

Jim

Tinks:
All the diffs are 3.54:1 in coil sprung disco, RR & defenders except that is the disco 2.

Hope this helps!!  :wink:

Jimbo:

--- Quote from: "Tinks" ---All the diffs are 3.54:1 in coil sprung disco, RR & defenders except that is the disco 2.

Hope this helps!!  :wink:
--- End quote ---


Hmm, putting 3.54 into the equation I get a result of 104mph @ 4200rpm in 5th gear - think somethings amiss with my truck somewhere  :(

I don't have a rev counter fitted, so can't be absolutely sure what rpm the engine is doing - but it sure sounds like its screaming, and the speedo (checked with 2 different GPS's) reads around the 70 mph mark. I've been reliably informed that a Td5 Defender will easily pull 90mph (not that I want to !), but I would like to be able to keep up with motorway traffic and not rag the nuts off the engine.

Tinks:
Wow, i have a disco 200tdi engine in my defender and that'll do 80 on the motorway with the pump turned up so i'd say something is definatly not right a standard TD5 you sit at 70mph a piece of ****!

Jimbo:

--- Quote from: "Tinks" ---Wow, i have a disco 200tdi engine in my defender and that'll do 80 on the motorway with the pump turned up so i'd say something is definatly not right a standard TD5 you sit at 70mph a piece of ****!
--- End quote ---


I also have a Td5 Disco, and that sits quite happily at motorway speeds, at about 2500rpm, I know the engine in Discos has a different ECU tune, but somethings definitely up with the Defender.

I'm guessing that maybe the t-box ratios have been messed with - its not as if the engine is lacking power as it pulls like a train up to 60.

Is there anyway of checking what ratio the diffs are for definite ?

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