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diff ratios, what to choose

Started by shanegtr , Jul 07 2006 06:10 PM

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16 replies to this topic

#1 shanegtr

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Posted 07 July 2006 - 06:10 PM

I'm currently running a 3.55 diff which was fine when the car was in perth. But with it up here its just to short. I used to have a 3.08 (until I busted it) which was pretty good on the road. I think the 2.78 would be a bit too tall, but would be really good for cruising. I'm running a 4 speed with views to a 5 speed in the future. The seat of the pants dyno didnt pick much diffence between the 3.55 and 3.08. Thinking back on it the 3.08 was a good around ratio. What do you guys reckon?

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#2 FastEHHolden

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Posted 07 July 2006 - 06:34 PM

I used to think 3.36:1 was a top allrounder but I would have to agree the 3.08 is a good all rounder but it leans toward highway use.

I have a 3.08:1 but about 90% of my driving is highway...I like it.

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#3 _73LJWhiteSL_

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Posted 07 July 2006 - 06:38 PM

I would agree 3.08 is a good all rounder. I had a 2.78 in the LJ, fantastic on the highway but terrible arround town, really boggy. I am running a 3.36 now and its good around town but reving a bit hard on the highway.

Go the 3.08 for the all rounder.

Steve

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#4 _gtr161s_

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Posted 07 July 2006 - 08:52 PM

If you end up fitting a 5spd i'd probably lean towards the 3:36 or 3:55, i had a 5spd with a 3:08 and found it laboured when you hit a hill.
The only prob with having short diff gears and a jap 5spd you'll find 1st will rev out to quick but thats the a small price to pay for the use off a 5th gear on the highway.

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#5 _LX8VD69_

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Posted 07 July 2006 - 09:06 PM

i have a 3.08 with my worked stroked 308 and i wouldnt have any thing else, i did at one stage seriously consider changing to a 3.36 but im glad i didnt

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#6 surfmaster

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Posted 07 July 2006 - 09:13 PM

If you do lots of open road work get a 2.78:1, with a fifth gear overdrive you will get great mileage, the trade off is the boggy start. If you have a fair bit of town work as well the 3.08:1 would be more suitable. Having said all that I had an LC with a 2850S and a 2.78:1 and an M20 which I used to drive all round Sydney, (not long after seat belts were mandatory front and rear and bullet resistant vests were not compulsory in some south eastern suburbs) and it went fine, a little slower off the mark but great legs on the open road.

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#7 rodomo

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Posted 07 July 2006 - 11:47 PM

I would agree 3.08 is a good all rounder. I had a 2.78 in the LJ, fantastic on the highway but terrible arround town, really boggy. I am running a 3.36 now and its good around town but reving a bit hard on the highway.

Go the 3.08 for the all rounder.

Steve

Hmmmm? More calculations for Winton. :tease:

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#8 _troy_

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Posted 08 July 2006 - 12:46 AM

I ran the 3.55 with the 4spd aussie slopbox,Just converted to the celica 5spd and stayed with the 3.55 ,wouldnt consider any other ratio

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#9 _73LJWhiteSL_

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Posted 08 July 2006 - 12:40 PM

I would agree 3.08 is a good all rounder. I had a 2.78 in the LJ, fantastic on the highway but terrible arround town, really boggy. I am running a 3.36 now and its good around town but reving a bit hard on the highway.

Go the 3.08 for the all rounder.

Steve
Hmmmm? More calculations for Winton.

Maybe you should have a look through the suspension section to work out what springs and shock and if i am running a swaybar or not. :tease:

Steve

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#10 shanegtr

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Posted 08 July 2006 - 05:10 PM

I used to have the revs for different diff ratios at 100, but cant find em anymore. Whats the difference between the 2.78 and 3.08? I just need a good gear set, as Im going to be using my LSD centre, I'll most likely end up going back to the 3.55 when the 5 speed goes in, but if the 3.08 goes alright then I can hold of on it for a while. While up here it will get a fair bit of the open road, 5 mins drive and I'm out on 110km roads, 10 mins and Im out on the open road :blink:

Edited by shanegtr, 08 July 2006 - 05:12 PM.

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#11 _73LJWhiteSL_

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Posted 08 July 2006 - 06:46 PM

I worked out for a 205/60R13 tyres at 100KPH RPM wil be:

2.78 ~ 2500 RPM
3.08 ~ 2800 RPM
3.36 ~ 3100 RPM
3.55 ~ 3200 RPM

Steve

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#12 _devilsadvocate_

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Posted 08 July 2006 - 07:04 PM

For torries with at least 173's, even 2.78's are undergeared for highway use with 13in wheels.
Unless your aim is to win traffic light drag comps then get the tallest diff possible for minimum noise and fuel consumption. Yeh, it might not pull well from 30kmh in top gear.......but isnt that why there are other gears in the box?
If going 5 speed route, check out what the overdrive ratio is, they vary from ~8-90%. If you run a 3.55 with a 5 speed with a 0.9 overdrive it will still be a buzz box.

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#13 rodomo

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Posted 09 July 2006 - 02:47 AM

I worked out for a 205/60R13 tyres at 100KPH RPM wil be:

2.78 ~ 2500 RPM
3.08 ~ 2800 RPM
3.36 ~ 3100 RPM
3.55 ~ 3200 RPM

Steve

Hmmmmm that gives a clue to your tyre size too. I've ran all this data through my calculator and have worked out the difference to be the amount of doors on the cars. The outcome is that your car has more doors to suck off :spoton:

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#14 _MY75LH_

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Posted 24 July 2006 - 10:39 PM

I run 3.00 LSD in my 9" behind my M21, down low she is a bit of a slug with the 14s but take her out on the freeway and just let her cruise on 100kays @ 1900 rpms till she runs outta fuel.

Accelleration is great at the tonne too!

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#15 _JNR_ATE_

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Posted 25 July 2006 - 12:48 AM

Lol, i run 3.55 on my TH350,
100kays, 3000Rpm

But seriously considering changing to 3.36 to get home twice from work on one tank of fuel.

Fuel going, going, gone.

Cheers
JNR_ATE