what final drive have I got?
Turbo Mini Forums

I took the car for a spin today as has been documented in the restoration thread, and was suprised at how high the revs were for the speed.

At 60 mph I was at 4000 rpm with 55 profile tyres on a 12 inch rim. I am assuming that the diff is now a 3.44 rather than the 3.1 which I had assumed was fitted.

The slightly smaller tyres won't have such a profound impact on a 3.1 diff to slow it down so much when the 60 profile manages 60 at about 3500 rpm?

sounds like a 3.7 to me

3.4 is about 3500-3600
3.1 is about 3200

all are from i can remeber when using the diffs

always looking for them bigger bunches of bannanas

Yep, 3.7

Though, how acurate is your speedo reading, best check it with sat nav

I always found 4000rpm at 100kmh (62mph) with a 3.44 and 10". The 165/55-12 wheels are very similar to 10s. I'll guess there's a 3.44 in there.

In my gear calc spread sheet, with 12" wheels (60 profile) and a:

3.71 you'd be doing 61.

With 3.44 and you'd be doing around 65mph.

And with a 3.1 you'd be doing 73.

So I'd guess 3.71

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

3.71? I guess you mean 3.76 or possibly 3.65.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Bloody hell! I wonder what it came out of as it didn't look messed around with. It is an early A+ non lined block. In all the technical books my mot tester looked in to try to find the exact timing we couldn't match the engine number. It has 12HA87AA on the tag.

Did any A+ engines even leave the factory with a 3.7 or 3.6 diff?

I think a 3.44 too, just to be awkward!

i'd say its most probably a 3.4 and your speedo is out.

With TD on that one.

My speedo on my 1380 (from an 89 Racing Green) reads about 75% true speed (police confirmed .. lol) with the 13s and a 3.44 diff and whatever speedo drive was in the donor box, they can be madly out.

Every day is a school day ...........

How fast and how expensive ...... the same question...

The speedo has been fine on the last 2 engines it was on. One on the car it came out of and the 998 in the car before I pulled it apart.

I will check it though. I dont think the smaller tyres help with speedo accuracy.

unforgantly the spedo drives are also different , there is one hell of a lot of engines with diffs and boxes which shouldnt be together.

my old mg metro had a 3.1 in it from new weres most had 3.44. i knew this as i was the second owner and the bloke never had any probs with engine or box.

but if speedo is right then a 3.76 or if speedo is out then proberlly a 3.44

always looking for them bigger bunches of bannanas

Sorry, meant Turbo Shed ..... turbo something .. who cares ... LOL

Every day is a school day ...........

How fast and how expensive ...... the same question...

Why not measure. Push the car one full round on the tyres, mark the crankshaft pulley before you start, and hey presto.... The FD!

That I say is a fine idea.

Assuming 1:1 drops and known gear ratio of whatever gear you choose to do it in?

Easiest to both calculate and push in fourth at a guess

Yep, its got the 3.4

I have also found the speedo is 8 mph slow. so better watch out for that. What could be causing that considering I have a smaller rolling radius than before. Wrong speedo drive?

Hi,
Speedo drive would be favourite, or wrong speedo for the drive, depending on which way you look at it! LOL
Cheers,
Gavin :)

VEMs Authorised Installer / Re-seller. K head kits now available!

WB/EGT gauges. Click here for customers write-up

Visit www.doyouneedabrain.co.uk

My Mini build diary