I just bought another disco 1 and the previous owner put some true tlc in this one, Arb bumper, warn winch, borla cat back, sd roof rack, ome lift and tires so I'd assume since he upgraded a lot of the stock components he also upgraded the differentials. I can't get ahold of him so that's why I come here. Those of you who are running 4:11 what are your Rpms? I'm running just above 2500 at 70mph. Mind you, I have 245/75r16

 

I can't recall my RPM's at 70. Mainly because I hardly ever go that fast. Use the Ashcroft calculator to figure out what your RPM's should be.

 

4.11 would be pretty low on a 245. I rarely see 70 in my truck and the tires would throw off the speed a good bit at that speed. The Ashcroft calculator that Brett mentioned is a good start. A good place to start would be to jack up both back wheels and turn one side. If the other side does not turn as well its not locked and its very doubtful that it is geared.

 

I run about 2100rpms at 60 with stock gets and 33s

 

Ashcroft Transmissions - Ratio Calculator

 

Thanks for all the the replies. I've been busy with work the past week or so but in the mean time I jacked up the front axle, put it in neutral and spun one of the wheels and the other didn't spin. Did the same to the back and the other spun in the opposite direction. I was in the engine bay, toppin up some fluids yesterday and I noticed that it has 7mm plug wires where as though my previous disco had 8mm but that wouldn't really make the performance different that much, would it?

 

The 7mm wires might not last as long in a hot engine compartment, but while they are still good they aren't going to perform any worse.

 

I plan on swapping them out today