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What Diff To Use


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#1 BuggyMan

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Posted 06 July 2011 - 09:42 AM

Hi I have a road legal off road buggy which I have bult with an A series 1000cc Mini engine. I have 12" wheels with chunky tyres it goes well but it struggle in 4th and does struggle with hill climbing as 1st gear is a little too high. I'm guessing I need to fit a non standard diff. Does anybody have any idea of which one I should use?

#2 Cooperman

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Posted 06 July 2011 - 09:59 AM

The basic optional diff ratios for Minis are as follows:

2.7, 2.9. 3.1, 3.2, 3.4, 3,6, 3.7, 3.9, 4.1, 4.3, 4.6

I've rounded the numbers to one decimal point, so please don't come on saying the ratio is 3.44, or whatever.
It depends on what you have at the moment and how much you feel it needs to change.

#3 BuggyMan

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Posted 09 July 2011 - 07:40 PM

The basic optional diff ratios for Minis are as follows:

2.7, 2.9. 3.1, 3.2, 3.4, 3,6, 3.7, 3.9, 4.1, 4.3, 4.6

I've rounded the numbers to one decimal point, so please don't come on saying the ratio is 3.44, or whatever.
It depends on what you have at the moment and how much you feel it needs to change.



Thanks for that. I am unsure what I have at the moment. I will need to strip it down and take a look. I just wondered if there was an advised ratio for the kind of set up I have. When running off road 1st gear is just not low enough, this shows itself by the engine giving up on a steep climb in first gear. Out on the road top gear drops off the power. I can cruise at around 60 in 3rd but as soon I drop in to top it falls back to fifty and then even further if I hit an incline. The engine and gearbox came from a standard 1000cc on a 1990 plate and I don't think it had been change from the original. I have rebuilt the engine with re-bore etc but didn't take much notice of the gearbox setup, wish I had now.

#4 bmcecosse

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Posted 09 July 2011 - 08:35 PM

Sounds like the engine may be down on power..... I would use a 4.1 diff (ex Austin 1100 etc ) or perhaps a 3.7 (ex early Minis)

#5 minilester

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Posted 09 July 2011 - 08:54 PM

i know its not what your asking but have you had it rolling roaded? as bmc said sounds like a power problem.. might be worth a shot b4 you swap diffs, and use a mini friendly roller as they should then tell you all you need to know about your engine/gearbox/diff if you ask nicely enuff. ;)

#6 BuggyMan

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Posted 10 July 2011 - 02:45 PM

i know its not what your asking but have you had it rolling roaded? as bmc said sounds like a power problem.. might be worth a shot b4 you swap diffs, and use a mini friendly roller as they should then tell you all you need to know about your engine/gearbox/diff if you ask nicely enuff. :thumbsup:



Yeh you're right about checking. I did think of the power thing and had it checked on a rolling road by a very helpful guy in cheltenham (SpamSpeed). He set up the twin 1 1/4 SUs and seemed to think that a diff change would help. I think its because of the big wheels. The output was:

Engine 52.7 hp
Wheels 38.5 hp
Power losses 14.2
Engine power corrected 53.1
Torquw 65lbs/ft

Which doesn't sound like its got a problem? Mid range with your foot down it goes really! well. Its the second one in this vid - http://www.youtube.c...nel_video_title
I think I will strip it down and see what's in there now




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