Birty Dastards Jeep Club
Tech Forum => Workshop => Topic started by: Grahampuk on December 21, 2012, 03:28:59 PM
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I purchased a 98 cherokee XJ, 4.0 ltr, manual, Dana 35 with 3.07 ratio, 4.5 lift with 32 inch tyres
The problem is the vehicle will only have a cruising speed of 65mph with a 2800 rpm and whenever I shift from 4th to 5th gear the vehicle does not have enough power and I must change back down to 4th and I know the engine power is ok.
My question is what do I need to do with the tyres, axles or gearing to be able to cruise at 75mph ?
Regards,
Graham
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cheapest way 4.10 axles off a 2.5 petrol
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Thank you for the reply,
What would that give me a cruising speed of ?
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Should return the gearing near enough to stock
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Go & check out Randy's Ring & pinion website, if you cant get the axle's off a 2.5, price up re-gearing what you have, at a guess your looking at £1200 - £1500 to get the parts this side of the pond.
Depending on where you are, I know a man that can do the work for you :icon_winkle:
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Thank you,
Don't think I can get stock axles from a 2.5 here in Middle East as all vehicles were 4.0, ordering is not an issue so what would you recommend I order ?
Regards,
Graham
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you jammy bastard, I bet you aint got frickin rain and cold assed wind :011:
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contact these guys
http://www.ringpinion.com/ (http://www.ringpinion.com/)
but you will need some one who knows what there doing
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Any idea which axles I should go for ?
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http://www.jeep4x4center.com/jeep-tires/tire-gear-ratio-chart.htm (http://www.jeep4x4center.com/jeep-tires/tire-gear-ratio-chart.htm)
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Try ECGS (http://eastcoastgearsupply.com) they are very helpful.
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4.56 would be better but may need more axle work than just gear sets
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I ran 33 inch tyres on my Tj with 3.07:1 gears for a while. Cruising at 70mph wasn't a problem. 5th gear was useless and not used at all, but it would cruise happily at 70 in 4th unless it was very windy, when I had to use third. If you can only get to 65 I'd say u have other problems than the gearing.
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Middle east, now that would explain the manual gearbox on a 4.0L.
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I ran 33 inch tyres on my Tj with 3.07:1 gears for a while. Cruising at 70mph wasn't a problem. 5th gear was useless and not used at all, but it would cruise happily at 70 in 4th unless it was very windy, when I had to use third. If you can only get to 65 I'd say u have other problems than the gearing.
He's probably doing more like 75-80 if he's running 32s on stock gears without recalibrating the speedo.
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Good point
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The Doc speaks good logic :icon_winkle:, double check that speedo with a satnav, the differences can be surprising :icon_eek:
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It is a point but I have had indicated speeds faster than 70mph in my TJ before swapping the speedo gear (Professional Driver on a closed course, do not try this at home). :eusa_whistle:
80mph shouldn't be an issue for an XJ with a rated top speed of over 100mph.
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I'm running 35"'s and. 4.56 on my TJ and the speedo has be redone to accommodate the above and there is still a difference between my Sat Nav.
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The speedo should read 5-10% faster than actual speed when setup right.
For the original question I would say 4.10 gears would be perfect with manual box and a driver who wants a good top end speed but do check actual speed and don't rely on the speedo to tell you as the bigger tyres have a massive effect. You could go 4.56 gears but it would be revving a bit cruising at 70+. There are some calculators around on Randy's ting and pinion and other sites that will give you revs at given speeds.
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Here's a good calc for speed at given rpm or revs at given speed...
http://www.grimmjeeper.com/gears.html (http://www.grimmjeeper.com/gears.html)
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Or even right here on this site
http://www.birtydastards.com/frm/index.php?action=ezportal;sa=page;p=8 (http://www.birtydastards.com/frm/index.php?action=ezportal;sa=page;p=8)