Diff ratios

Submitted: Monday, Aug 12, 2002 at 00:00
ThreadID: 1699 Views:8209 Replies:5 FollowUps:4
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I have a 2.5lt T/D Mitsubishi Delica (import), which basically runs Triton/Pajero running gear. The vehicle is quite good in most areas, and pretty much does the job that we ask of it. However at highway speeds the engine is turing over quite quickly, 100klm/h equates to 3000rpm. Should I be playing with diff ratios, and or wheel/tyre sizes, to improve highway travelling?
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Reply By: Savvas - Tuesday, Aug 13, 2002 at 00:00

Tuesday, Aug 13, 2002 at 00:00
Other than having seen a few around on the roads, I'm not very familiar with the Delica. The first question that comes to mind is what sort of transmission is it running, and does it have an overdrive ratio? My auto Jackaroo runs something like 3000rpm (can't remember exactly) when held in 3rd gear at 1000rpm.
AnswerID: 5635

Follow Up By: Redneck - Tuesday, Aug 13, 2002 at 00:00

Tuesday, Aug 13, 2002 at 00:00
The Delica is a 5 spd manual, with duel range four wheel drive, to my knowledge the same transmission, transfer case, diff housing etc as the Triton of the early nineties.

Boris
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FollowupID: 2446

Reply By: Eric - Tuesday, Aug 13, 2002 at 00:00

Tuesday, Aug 13, 2002 at 00:00
Boris
I have a triton with similar drive line. I put biger wheels on it for the same reason but took them off agian when I was unable to reverse in sand, so check that you have the ability to reverse up a steep slope when fully loaded before you change anything. There are alternative fithgear ratios avaible from other boxes ie sigma [jap box].
Eric
AnswerID: 5664

Follow Up By: Redneck - Tuesday, Aug 13, 2002 at 00:00

Tuesday, Aug 13, 2002 at 00:00
Thanx for the reply Eric, when you did have the bigger wheels on the Triton, what was the difference on the highway? was there any gain, or was it not worth the expence?
Also, I don't suppose you know of anyone trying the Sigma fifth gear mod, and the result of such a mod?

Boris
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FollowupID: 2453

Reply By: Derek - Tuesday, Aug 13, 2002 at 00:00

Tuesday, Aug 13, 2002 at 00:00
Hi Boris. I had a Mitsubishi L300 van and although not real flash off road was one of the most versatile 4x4s I ever owned. I raised the suspension and fitted 10R 15 tyres which improved its off road ability considerably but killed the acceleration and reduced the cars braking ability. I solved the acceleration problem by working the motor a little, but there was nothing I could do for the brakes. 3000rpm sound fine as this is what most 4x4 four cylinder engines pull for 100kph. Be warned. If you raise the front end too much by screwing up the torsion bars, you run the risk of popping a front axle out of the diff centre. Good luck, they're a great car.
AnswerID: 5665

Follow Up By: Redneck - Tuesday, Aug 13, 2002 at 00:00

Tuesday, Aug 13, 2002 at 00:00
G'day Derek, I also agree that this is a very versatile vehicle, as an owner of four children, I need the space. I have found the Delica very capable in the bush. The look on the faces of the crowd gathered at the river crossing at Twin Falls (Kakadu) last weekend when we came around the corner :) and just trundled across, disappointing....
So it's normal to be revving at around 3000 at 100klm/h?? If I sqeeze it up to 110, you can almost see the fuel gauge drop...


Boris
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FollowupID: 2454

Reply By: Derek - Tuesday, Aug 13, 2002 at 00:00

Tuesday, Aug 13, 2002 at 00:00
Hi Boris. I had a Mitsubishi L300 van and although not real flash off road was one of the most versatile 4x4s I ever owned. I raised the suspension and fitted 10R 15 tyres which improved its off road ability considerably but killed the acceleration and reduced the cars braking ability. I solved the acceleration problem by working the motor a little, but there was nothing I could do for the brakes. 3000rpm sound fine as this is what most 4x4 four cylinder engines pull for 100kph. Be warned. If you raise the front end too much by screwing up the torsion bars, you run the risk of popping a front axle out of the diff centre. Good luck, they're a great car.
AnswerID: 5666

Follow Up By: Urro - Wednesday, Sep 25, 2002 at 00:00

Wednesday, Sep 25, 2002 at 00:00
Hi Boris
I can only confirm what Derek is saying.

Beeing a member of an European forum specializing in Mitsubishi 4x4's + Hyundai Galopper we've discussed this topic of the hight rpm's at already 100km/h, over and over - the L300 is just no racing engine.
... but a perfect car to rediscover the advantages of beeing slow.

Some of our members experienced the same issues with enginepower, but -even more important- breaking issues.
Due to the fact that there is not too much space (in width) in the front roadhousing some L300 owners are thinking about fitting 235/85 R16 wheels instead of the original R15's - however the extra weight of the wheels is substantial + therefore leading in breaking problems.

The L300/Delica has the same engines/gearboxes/axels as some Pajeros + can therefore be exchanged - however you would have to make sure all parts have the same transmition ratio (there are at least 4 different variations).

cheers from Switzerland
urro
who has been in the Sahara with his L300 :-))
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FollowupID: 3128

Reply By: Eric - Wednesday, Aug 14, 2002 at 00:00

Wednesday, Aug 14, 2002 at 00:00
Boris.
The result of fitting the bigger wheels can be calculated it is simply a direct ratio of size ie 20% bigger is 20% faster but unless you change the calibration on the speedo the revs/ kph will appear the same.
With the fifth gear ratio that is a matter of finding out what ratio you have now and comparing it to the sigma which is .856 the 2wd triton is .827 you can see the change is small and probably not worth doing.I have rebuilt several gear boxes, it is a lot of work unless you are taking out the box for some other reason. My triton has done many long trips and the revs has not proven a problem if you stay under120.
Eric
AnswerID: 5718

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