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Discussion Starter · #1 ·
hey, just curious to see what revs peoples cars are doing with 35s and 4.1 ratios. I'm trying to figure out if my ratios have been swapped already or not.
currently my gu ute does 2150- 2200 rpm at 100kms, that's going off a gps as the actual speedo is out.

my old man has a gu ute also with standard size tyres and 4.1s and his does similar revs so it has got me thinking if mine have already been swapped, I would have thought mine would be a lot lower than his if mine was still standard
 

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Discussion Starter · #3 ·
yeah ok cheers, so only other way to check would be to pull diff centers out and count the teeth, maybe when i find a weekend free ill get around to it.
anyone have 4.3 or 4.6s able to tell me what revs urs r doing at 100km
 

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Previously known as twodiffs
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yeah ok cheers, so only other way to check would be to pull diff centers out and count the teeth, maybe when i find a weekend free ill get around to it.
anyone have 4.3 or 4.6s able to tell me what revs urs r doing at 100km
No thats not right...have a search, there is info somewhere on gearing that says how to determine gearing by spinning the wheel and counting the pinion/driveshaft turns.

I can't remember where it is but if i find it i'll post the link...would be a lot easier eh ;)
 

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I have an 03 4.2 Ute on 315/75x16's. At 100km/hr by the GPS I am doing 2150RPM on 4.1's (as far as I know). Am hoping to get some 4.3's under it soon.
 

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hey, just curious to see what revs peoples cars are doing with 35s and 4.1 ratios. I'm trying to figure out if my ratios have been swapped already or not.
currently my gu ute does 2150- 2200 rpm at 100kms, that's going off a gps as the actual speedo is out.

my old man has a gu ute also with standard size tyres and 4.1s and his does similar revs so it has got me thinking if mine have already been swapped, I would have thought mine would be a lot lower than his if mine was still standard
Hi jakeyp, here are some rough calcs for you:

Circumference = diameter x pi = .889m x 3.14 = 2.793m
Tyre rpm at 100kph = 100000 / 2.793 /60 = 597
Rpm in 1:1 gear @ 100kph with 4.1 diff = 597 x 4.1 = 2450
Rpm in 5th gear (.85) @ 100kph with 3.9 diff = 597 x 3.9 x .85 = 1980
Rpm in 5th gear (.85) @ 100kph with 4.1 diff = 597 x 4.1 x .85 = 2080
Rpm in 5th gear (.85) @ 100kph with 4.375 diff = 597 x 4.375 x .85 = 2220

It is of course also possible that your rpm gauge is not reading accurately ;)

Cheers,
Whitie
 

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mine does about 2600 rpm in 5th [email protected] with 35's on and 2700rpm with 33's, I have 4.375's in mine being the 4.8 patrol
 

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mine does about 2600 rpm in 5th [email protected] with 35's on and 2700rpm with 33's, I have 4.375's in mine being the 4.8 patrol
That is weird, they are the rpms you should be doing if you were in 4th with that setup :confused:
 

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That is weird, they are the rpms you should be doing if you were in 4th with that setup :confused:
my previous 4.5 patrol was lower with 35's and 33's likewise about 2400 & 2300rpm and they run 4.1's, my mates 4.8 runs the same as mine
 

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with 3.0 engine and automatic transmission, 2000 rpm corresponds to 100 km on Gps
 

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my previous 4.5 patrol was lower with 35's and 33's likewise about 2400 & 2300rpm and they run 4.1's, my mates 4.8 runs the same as mine
Mmmm, it is possible that the rpm gauge is out if you are marking the speed with a GPS.

Yours should be around 2300rpm at that speed:
Rpm in 5th gear (.88) @ 100kph with 4.375 diff = 597 x 4.375 x .88 = 2300

Do you have a scangauge to confirm what the ECU is reading compared to what the rpm gauge is displaying?
 
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