The Triumph 2000 / 2500 / 2·5 Register Forum

I have a mk1 estate. '68. It has A type O/D which works now. However, top end is very strained. The diff is probably 4.1:1. Is this not helping. Is it easy to swap to a better ratio and what is all round best. Would a 3.7 make it more relaxed top end and if so, would this have to come from an auto. If so would it fit ok. How would I find one (that works) if this is needed. Jeff

Hello Jeff,
Sorry I can't give you an answer.
But I'm surprised. I have exactly the same configuration on my 2000 (1966) and I use it on the highway as a modern one without difficulty.
GPS cruising speed at 120-130km/h (75-80 mph). Top speed (without exploding the engine...) probably around 90 mph.
Do you want/need more? What's your actual top speed maybe the ratio is not the problem?
Fabien.

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Your car should have been fitted with a 4.1:1 diff from the factory. The serial number should start MB. This should give a reasonable pick up from the line, and a good cruising speed. I have not seen it really necessary to change to a 3.7:1 although the post 1975 cars had these. These 3.7 diffs are colour coded yellow on the inside of the flanges. A 3.45:1 (colour coded red) as fitted to the 2.5 cars is too far!

Why do you say too far? I was considering swapping the diff in my 2000 to a 3:34. Is this not a good idea?

It will have great low revs at speed, but will be very slow off the mark, and need to drop a gear on the smallest of hills!

Charles H wrote:It will have great low revs at speed, but will be very slow off the mark, and need to drop a gear on the smallest of hills!

I'm very much with Charles on this.

MUT

I have had a look at the wheels and they are 195 55 r15 as they are on minilytes. Using a speedo check calculator this should bring a difference of 3 miles/hour below, which means to get to 70 I need work a bit more as on dial at 70 the car is doing 67. Ideally 205 55 r13 would have been far better match. 70 dial, 70 in real world.

I have had carbs balanced, has had a new coil and plugs, distributor and electronic ignition, compression is OK and I have played with timing but will have a go at this again.

3.34 will be too low geared. Won't pull away, well, very slow. Unless you have serious torque to overcome it. I.e. V8 torque! I need to change my 3.45 for a 3.7 as the bottom end punch is a bit lacking. Any one got a good 3.7 Stag diff they want to part with?


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Alan, I always thought those big tyres on 15 inch rims plus 3.45 diff was a bit optimistic for a manual stag - they love to REV - triumph weren't daft fitttinga 3.7 to the manual - maybe the auto could have coped with a 3.45 although it really needed a 4 speed auto!