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What low ratio LSD diff would fit in my car? 

 

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 Post subject: What low ratio LSD diff would fit in my car?
Posted: Wed Jul 22, 2009 11:17 am 
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G'day guys, I've finally getting around to getting a new diff to replace my 2.77..

It's going into an '88 DA LTD, which of course has the longer wheelbase of the wagon but still has coil springs.

I'd really prefer to just bolt it on as it is my daily driver and I' not really allowed to do too much work at my unit thingy (bloody body corporate).

I was thinking of either a 3.89 or 4.11, but I've still got the three speed auto box in my car, can anyone tell me what I can expect it to rev at in third gear at 80-100KM/H?

Also, my mate reckons there is a difference between a manual and an automatic differentials in falcons, is this true?

Cheers.

 

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 Post subject: Re: What low ratio LSD diff would fit in my car?
Posted: Wed Jul 22, 2009 6:03 pm 
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there is a difference... the ratios... other than that no difference afaik. i took my (5spd) single spinner 2.92 out and put in a 3.23 from an auto, whole assembly.

you should be able to use a common coil spring diff as long as you utilise your tailshaft (which i think is a wagon one) and make sure the uni joints are in the same arrangement eg: flanged or the 'strap' type for lack of better description, theres only two though as far as i know.

 

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 Post subject: Re: What low ratio LSD diff would fit in my car?
Posted: Thu Jul 23, 2009 3:45 pm 
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Alright, cheers mate.

Happen to know roughly how much higher it would rev in third gear at about 80KM/H?

 

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 Post subject: Re: What low ratio LSD diff would fit in my car?
Posted: Thu Jul 23, 2009 7:29 pm 
Getting Side Ways
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if you can suss out the search thing here or google search for diff ratio speed convertors or similar theres at LEAST one on this site and heaps out there. where you input your current setup, then change the ratios and it generates the difference.

everyone giving opinions would be fairly variable i would imagine.

 

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 Post subject: Re: What low ratio LSD diff would fit in my car?
Posted: Thu Jul 23, 2009 7:43 pm 
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you will be revving the bollocks off it on the highway.

I have a t5 with 3.89's and it sits on 2600 rpm at 110 kmh.

the three speed would be unfeasable on the motorways with 3.89's- 4.11s.

why do you think they ran the 2.77:1 in the first place?

You need to ditch the three speed more so than swap the diff ratio. 3.23's might be ok on the three speed, but the problem lies more with the lack of overdrive in your gearbox.

 

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 Post subject: Re: What low ratio LSD diff would fit in my car?
Posted: Mon Jul 27, 2009 12:46 pm 
Getting Side Ways
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Cheers for the help guys.

Is a four speed auto's final drive ratio much better than the three speed?

I'd really like to keep it auto 'cos I drive it as a daily and my XC will be manual :D

 

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 Post subject: Re: What low ratio LSD diff would fit in my car?
Posted: Mon Jul 27, 2009 7:26 pm 
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heaps better top gear ratio in the 4 speed, about .68:1 from memory, where i think top in a 3 speed is somewhere around the 1:1 mark.

 

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 Post subject: Re: What low ratio LSD diff would fit in my car?
Posted: Wed Jul 29, 2009 1:34 pm 
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Great, thanks mate. I guess I'll start looking for a 4sp box and ECU to suit in tas in reasonable condish without getting it from a wreckers which will cost a s**t.. Too easy :p

 

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 Post subject: Re: What low ratio LSD diff would fit in my car?
Posted: Thu Jul 30, 2009 10:59 am 
Getting Side Ways
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the 4 speed will give you more flexibility in diff choices as well.

when I was running the 3.89's behind the btr, it cruised the freeway 110kmh at around 2500 rpm, and was really very quick off the line.

For lower highway rpm, and exceptional takeoff you can chuck in a set of 3.45's, and get the best of both worlds.

a 4 speed with 2.77s will be a dog off the line, but will get more than 100kmh out of first gear at redline :)

probably doing around 1500 rpm in 4th at 100kmh too.

 

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