Effect of oversized tyres on gearbox

Submitted: Monday, Jul 25, 2005 at 18:12
ThreadID: 25037 Views:1969 Replies:3 FollowUps:5
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I've Coopers 315x75x16 tyres on my Landcruiser 80 series. Will this have an effect on the gearbox? Do I need to change the gear ratios to match the tyres? Anyone has gearbox problems with oversized tyres?
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Reply By: big red car - Monday, Jul 25, 2005 at 18:53

Monday, Jul 25, 2005 at 18:53
i have been running 35's on my 62 series for about 5 years and so far so good,i turn them with a 6.5lt chev diesel, but i am careful not to load up 4th and 5th, don't slot 5th until about 75k's an hour. hope that helps!!
AnswerID: 121970

Reply By: GO_OFFROAD - Monday, Jul 25, 2005 at 20:43

Monday, Jul 25, 2005 at 20:43
running 37's on the GU and I went 4.88's in the diffs to make the gearing standard, works very well, and would highly recommend it.
AnswerID: 122004

Follow Up By: warthog - Monday, Jul 25, 2005 at 21:15

Monday, Jul 25, 2005 at 21:15
I like the idea of swapping crown wheel and pinion but have been put off by what I imagine it is going to cost given I don't know how to do it myself. Can you give me a rough idea of the cost involved?
Cheers.
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Follow Up By: at4x4 - Monday, Jul 25, 2005 at 21:23

Monday, Jul 25, 2005 at 21:23
damn puter logged me on as go_oofroad again, oh well,
you would be looking around $150-$200 a diff for set up, + remove and replace, if you cant do the easy bit.

But if the price puts you off, you should probably stick to the tyres you have, because 315's will add cost in wear and tear, fuel consumption etc.
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FollowupID: 377159

Follow Up By: warthog - Monday, Jul 25, 2005 at 21:54

Monday, Jul 25, 2005 at 21:54
Thanks, was thinking 4.3 or 4.6 and 285's. I've already spent a bit on it and the wife is getting harder to convince.
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Follow Up By: BenSpoon - Tuesday, Jul 26, 2005 at 20:50

Tuesday, Jul 26, 2005 at 20:50
what what what?? $150-200 for a new gear set??
The cheapest price I found was $530 an end, and that was after scouring the country from west to east.
The alternative is to put in some new ratios in the gearbox, but that involves dropping the box, which I swear I will never do again on a cruiser. The added cost of the bigger rubber ($100 more per tyre for an extra 2" diameter seemed common) and the cost of mechanical parts needed kept me at 33"s.
A local 4by shop here runs a diesel 80 on 35"s with stock running gear- They have reported no dramas on the drive train. Just get a caster correction to fix the front diff angle or you'll bust uni joints I am told.
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Follow Up By: at4x4 - Tuesday, Jul 26, 2005 at 21:28

Tuesday, Jul 26, 2005 at 21:28
the gear set is extra......
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Reply By: fourplayfull - Monday, Jul 25, 2005 at 23:06

Monday, Jul 25, 2005 at 23:06
Done approx. 40000 kms. running 315's towing a ct behind 80td manua with no hithes , brouht the gearing up just right - certainly change into 5th after 80 kph .
AnswerID: 122034

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