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Isuzu FSR 14 Sep 2015 17:17 #162151

  • mammoth
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Have got a '95 FSR 500 na at a good price. However at 100 clicks she is doing 2600 rpm so I am looking for either a faster diff and/or an overdrive box. Is it better to go for the 6 or 5 speed overdrive? and any issues I should be aware of?

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Re: Isuzu FSR 14 Sep 2015 18:40 #162152

  • jon_d
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Mammoth,

I've got a 6BG1 TC 6 speed overdrive in my Bedford Comair

Go the overdrive with air clutch and air cables.


2nd: 4.244
3rd: 2.58
4th: 1.54
5th: 1
6th: 0.763

I do 100 at just under 2500 (8.25x20) 5.83 diff

I'm happy to chug along at 80-90 at 2000-2200 rpm. It's a Jap engine and they say they like to rev a bit.

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Re: Isuzu FSR 14 Sep 2015 20:16 #162153

  • Bitsa
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G'day mammoth
I have driven a few Isuzu's and they all seem to handle 2 to 3000 revs quite happily, but I have found that they are a bit thirsty when doing it. As jon-d has said, they are quite happy just chugging along. Maybe a higher diff is the go if you don't have too many hills.
Cheers
Alistair
1990NKR Isuzu&&1974 D1310 4x4&&195? Chamberlain Dere Backhoe&&743B Bobcat&am

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Re: Isuzu FSR 14 Sep 2015 21:19 #162154

  • mammoth
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It is all hills around here, and at 1000m altitude, which is part of the story behind upgrading from the Dyna = like stepping out of a Barina into a commodore :D. Admittedly with no tray but went all the way up Cunninghams Gap in top. 8-)
Mine has the later HE1 motor which has slightly lower rev rating

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Re: Isuzu FSR 17 Sep 2015 20:08 #162155

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Did turns of the wheel and turns out I already have the fastest diff (4.333/1). Wreckers are wanting $3k plus for an overdrive box so might bide my time.
Has anyone put bigger wheels on, say 19.5 tubeless or even 8.25R20?

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Isuzu FSR 12 Jul 2016 09:29 #172126

  • ashmenz0
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Hi Mammoth
I have the Isuzu MBG6P overdrive box with 4.88 Eaton no 4 in our bus. I also have 10.00/20 tyres which gives me 100km/h at about 2000 rpm.
In direct I get 80km/h at 2000 rpm. Perhaps larger tyres with that diff might get you where you want.

There is a great calculator on the net. Go to " www.csgnetwork.com/speedcalc.html " You need tyre diameter, gearbox and diff final ratio and you can then play around with the revs. This is what I used to get mine close to what I wanted.
Hope that helps
Ash
The following user(s) said Thank You: tim

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