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auto/manual diff ratio? 

 

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 Post subject: auto/manual diff ratio?
Posted: Tue Apr 05, 2005 7:14 pm 
Getting Side Ways
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i was thinking about going manual coz of the tall first gear in the auto on my ea but im kinda lazy and like my auto was just wondering is there something else i can do to get that better accleration out of the auto i really dont like that first gear also when flooring it from first take off it seems ages to change gear and the revs seem high....if anyone can help me...maybe a diff gearbox or change the gear ratio? i dunno thanx in advance....

also was wondering why the autp doesnt let me smoke up at stand still? not a thing i do all the time seeming ive got 235/45/17's and are kinda dare but its nice to know u can
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Posted: Tue Apr 05, 2005 7:29 pm 
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A shorter (? Fractions and ratios screw me over bad) diff ratio will help with takeoffs but decrease fuel economy as well as top speed.

 

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Posted: Tue Apr 05, 2005 7:37 pm 
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go 3.45's - best of both worlds. as per fitted to XR's etc.

 

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Posted: Tue Apr 05, 2005 7:53 pm 
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Or even 3.73 diff ratio i did it to and all round drivability is heaps better even wips the commodre sixs!
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Posted: Wed Apr 06, 2005 7:41 am 
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whats the diff between 3.45 and 3.73 ? much ? also wuts the price on doing that and does it wouldnt affect your speedo at all would it
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Posted: Thu Apr 07, 2005 1:49 am 
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the diff ratio is simple... its the amount of times the diff flange rotates for the wheel to rotate once.

For example, if your revving at 2000 RPM, in 3rd(auto 1:1), and you have a ratio of 3.45, that means that your wheels are spinning almost 580 times a minute. meaning a 3.73 would be spinning the wheels at just over 536 revolutions per minute. Meaning your car will rev higher, but take off quicker.

It does effect the speedo, and it needs to be calibrated after a diff change. The price, on just a gear change depends. You'll need to change the housing to a 3.23 or a 3.45 diff housing, cos the 3.45 or 3.73 gears don't fit in your 2.92, or whichever you have. So its easier to buy a 3.45 disc to disc diff assembly. I know a 3.23 (disc to disc) is about $400 from a wrecker. And the seperate 3.45 gear is around the $250 or so mark second hand. Just have to shop around.


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Posted: Thu Apr 07, 2005 2:00 am 
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I've also seen complete 3.45 LSD diffs for sale in Perth for around the $400-450 mark. Check a few places like Walliston Wreckers etc, should have one or be able to source one for you. I'd recommend the 3.45 though, with the autos ratio it should be what your after.

 

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Posted: Thu Apr 07, 2005 2:22 am 
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I've got 3.45's in my ED and I don't like them, going back to the 3.08 .

Hardly notice any difference in take off .
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Posted: Thu Apr 07, 2005 7:01 am 
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so would i be better off getting 3.73 and a 4 speed auto for better take off and the higher speeds? i dont really want it reving to high while cruising at the moment at a 100 its sitting at 1 and 3/4
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Posted: Thu Apr 07, 2005 5:05 pm 
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Slap in 4:11's and your baby bunny hopping on take off. :D

ps - forget about cruising at 110km without screaming to your passengers.

pss - my mates has 4:11's in his SS (6 speed man), so it isnt too bad in this case.

 

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Posted: Fri Apr 08, 2005 1:23 pm 
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au2low is absolutely right about changing to 3.45 not making much difference to takeoff - I went from 3.08 to 3.45 and noticed virtually no difference.

IMO if you're after harder takeoff with an Auto then you need to go to at least 3.7 - but be mindful of the implications for top speed.

For your speedo "calibration" you need to just get the correct Vehicle Speed Sensor gear installed to suit the diff ratio.

Best option all round might be just to get a higher stall converter - but there can apparently be issues with the trans computer dropping into Limp Mode?? - I always thought 2500 stall would be fine but I'm reading that some people have problems even with that and the ECU going into Limp Home Mode.

 

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Posted: Fri Apr 08, 2005 4:00 pm 
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Mine sits at 2000rpm with the 3.73 diff gears in my auto ef. Spending the money was well worth the improvement IMO
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Posted: Fri Apr 08, 2005 5:13 pm 
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Yep, 3.73 sounds the go - but 3.45 is a waste of time IMO.

 

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Posted: Fri Apr 08, 2005 8:29 pm 
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how much power does an auto actually rob?
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Posted: Sun Apr 10, 2005 12:58 am 
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Some of the old slushboxes used to take up to 30% but I don't know how much a modern auto takes.

 

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