mtentori New Member 3 Member For: 13y 8m 8d Gender: Male Location: Perth, WA Posted 10/10/11 04:50 AM Share Posted 10/10/11 04:50 AM Hi all,I have an 02 BA XR6T 4 speed auto. Mostly stock at the moment.I am going to do the exhaust, injectors, pump, valve springs, tune etc, hoping for around 400hp at the wheels.Would changing the 3.45 diff ratio to a 3.73 ratio be worth it as well? My main issue with the car at the moment is that it feels slow & heavy, and rather too sedate. I imagine that a shorter ratio would improve responsiveness & make the accelleration feel sharper all round? Or is the 3.73 not enough of a change from the 3.45 to make a noticabile difference? I am mostly looking to make the car more fun to drive, right now its abit boring and doesnt really inspire me to push it.Would the power upgrade make the car feel sharper & more snappy, hence not needing to fork out for the diff ratio upgrade (& put the coin aside for when/if the auto box goes)? Or is a diff ratio upgrade needed to get the most out of the car at speeds under 120km/hr?Thanks. Link to comment Share on other sites More sharing options...
j.d Member 1,222 Member For: 14y 7m 1d Gender: Male Location: Eastern Suburbs, Melbourne Posted 10/10/11 05:09 AM Share Posted 10/10/11 05:09 AM wouldn't you want longer ratios so that you can build more boost ?with those mods your car will feel better anyway! Link to comment Share on other sites More sharing options...
MiKa Donating Members 4,243 Member For: 18y 6m 7d Gender: Male Location: Melbourne, VIC Posted 10/10/11 08:33 AM Share Posted 10/10/11 08:33 AM Save for the auto mate.. Link to comment Share on other sites More sharing options...
mtentori New Member 3 Member For: 13y 8m 8d Gender: Male Location: Perth, WA Posted 10/10/11 09:45 AM Author Share Posted 10/10/11 09:45 AM Topic heading was supposed to be 3.73 Ratio Upgrade "Worth" It? Not "with it". Anyway what's the general power level the 4 speed auto can handle? Having trouble finding answers using the search function Link to comment Share on other sites More sharing options...
Mr_4.0 Member 1,096 Member For: 14y 1m 9d Posted 10/10/11 09:55 AM Share Posted 10/10/11 09:55 AM With a 4 speed auto I'd try 3.9's or 4.11's. You will only be reving to 2450rpm at 100km/h. Link to comment Share on other sites More sharing options...
Worm A much better forum Silver Donating Members 3,808 Member For: 16y 7m 5d Gender: Male Location: Victoria Posted 10/10/11 11:17 AM Share Posted 10/10/11 11:17 AM Max power stock 4 speed... Anywhere from 250rwkw to 330rwkw depending on tuner, auto cooler and how it's driven...Most would say don't go past about 250 if you don't have the cash to pay for a new built one!!! (about $3-4k) Link to comment Share on other sites More sharing options...
Worm A much better forum Silver Donating Members 3,808 Member For: 16y 7m 5d Gender: Male Location: Victoria Posted 10/10/11 11:19 AM Share Posted 10/10/11 11:19 AM And you won't hit 400hp @ the wheels with stock cooler and piping... Link to comment Share on other sites More sharing options...
Paulie2256 Donating Members 7,441 Member For: 16y 3m 6d Gender: Male Location: SE Melbourne Posted 10/10/11 12:08 PM Share Posted 10/10/11 12:08 PM the taller the gear (lower the ratio) the more load on your engine and your car will accelerate slower but you will see better top end. you are on the right track with the 3:73. 4th being an overdrive gear at a ratio of 0.6x or thereabouts in the btr will see you rev at around 2k at 100kms with a noticeable increase in acceleration. the shorter diff ratio will also be kinder to your engine but as you mod your car and power figure increases your gears will rev out a lot quicker. if you want to keep your car at around 300kw I would think about doing it last on the list otherwise not worth the coin. Link to comment Share on other sites More sharing options...
mtentori New Member 3 Member For: 13y 8m 8d Gender: Male Location: Perth, WA Posted 11/10/11 03:16 AM Author Share Posted 11/10/11 03:16 AM Ok thanks guys, some good advice in here Link to comment Share on other sites More sharing options...
Henz Tampon inserted, Auto Acquired, next purchase a new handbag Donating Members 9,946 Member For: 16y 11m 8d Gender: Male Location: Vic Posted 11/10/11 05:49 AM Share Posted 11/10/11 05:49 AM Also, your top speed if you plan to go Drag racing often may be affected, you don't want to be changing into 4th at WOT in your 4 speed.But a set of 3.9s/4.11s will really wake up the way it gets moving. Link to comment Share on other sites More sharing options...
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