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Front diff interchangeability: The true answer


WJM
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Sorry to drag up this old post. And apologies if it has been answered elsewhere. I just want clarification on something - coz I saw it mentioned. Can a Full Time 4WD D/R RX Box be made to take one of these LSDs?

 

If so, this would affect the ratio? yes? I had heard you cannot change the ratio of these boxes from 3.7..?

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it technically doesnt change the ratio, it just is an "implant" to make your front diff have a helical or clutch type engagement when wheel slip is created.....correct? and you can change the front diff ratio, right? by swithing to the 3.90 or 4.11 front diff, since they are apparently ALL interchangeable.

 

 

 

 

 

 

~Josh~

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Did you guys even READ the thread??????????????????????????

 

Can a Full Time 4WD D/R RX Box be made to take one of these LSDs?

 

No, it cannot be MADE to take one. ZERO modification nessisary. Direct drop in. You cannot modify the box to 'take' one...you dont have to, it drops right in.

 

If so, this would affect the ratio? yes? I had heard you cannot change the ratio of these boxes from 3.7..?

 

Would not change ratio. Yes, you can change ratios. 3.700, 3.900, 4.111, 4.444 are avalible.

 

and you can change the front diff ratio, right? by swithing to the 3.90 or 4.11 front diff, since they are apparently ALL interchangeable.

 

Yes, you can change front diff ratio, but you better change the rear accordingly. The diffs are the same, there are no 3.700, 3.900, 4.111, 4.444 front diffs. Ring-Pinion set defines ratios.

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Did you guys even READ the thread??????????????????????????

 

 

Yes, you can change front diff ratio, but you better change the rear accordingly. The diffs are the same, there are no 3.700, 3.900, 4.111, 4.444 front diffs. Ring-Pinion set defines ratios.

 

Oh I read the thread alright. As you can see in my post I was after clarification - coz I have been told otherwise. I have been told, from various sources, it is impossible to fit any other ratio than the 3.7 into a Full Time 4WD Box. It can be done, however (apparently), in the Part Time Boxes

 

I have had no personal experience in doing this - and I am certainly not going to say you are wrong. I just want to find out why I have been told differently.

 

I guess this is really a separate issue to the Front LSD though!

 

Thanks for your reply WJM :)

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OBX makes good stuff.

 

I do not have it installed yet.

 

welll.... I'mma wait until you put it in and run it for a bit :lol: being innovative is one thing but blowing $450 sucks... it seems to be either $450 or $1k... I'm not gonna pay $450... just to blow it up and have to fix it.. so if it works out for you I'll go OBX, otherwise it'll take me a while to get $1k to drop into a car I've never driven over a quarter mile???

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so that means get on da ball Will...

 

I've got a spare RX FT tranny and I'm waiting... waiting for a good day to tear it down and put one in;)

 

 

my tranny is out.. for now I'm being stubborn and refusing to reinstall until I can get a limited slip... story will change if the legacy breaks though

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  • 8 months later...

I wana do both!!! But the rears easiest for me to get-to!.... Or im just 2 lazy to go to the front!!! and if i did do an only front lsd it would understeer more than a fwd car does anyway!!! are you guys using this for street or for off-road!

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I saw the picture of tranny aprt in other thread. Could the final drive gears be swapped cleanly to a 2wd shaft from an 88 gl-10 with the 3.454 final 4wd? I am assuming that is the final gear in referenced on the manual.the ring and pinion, or front lsd, or other name for it. It looks like it can be taken out via a key? or set threaded pin?

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So the front diff assy is the same P/N from 1985 to 2004... check.

 

So as I gather, a 5spd D/R could be swapped to a legacy front LSD with no issue. (note to self: swap from 4spd D/R to 5spd) I guess the next question, pardon me for asking as I dont recall reading about it in the thread, is of the various gearsets.. will the 4.11 and 4.44 also pop into the case without modification? I ask this as I've read in various other threads that those two sets, 4.44 in particular, uses a larger diameter ring gear.

 

And, as a logical extension of the above question, what sort of options exist for the rear end? Or is dropping the R160 in favor of an R180/200 the only option to fit those extended gearsets? *prepares to cut up a 280ZX for its 4.11 R200 lsd* :grin:

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So the front diff assy is the same P/N from 1985 to 2004... check.

 

So as I gather, a 5spd D/R could be swapped to a legacy front LSD with no issue. (note to self: swap from 4spd D/R to 5spd) I guess the next question, pardon me for asking as I dont recall reading about it in the thread, is of the various gearsets.. will the 4.11 and 4.44 also pop into the case without modification? I ask this as I've read in various other threads that those two sets, 4.44 in particular, uses a larger diameter ring gear.

 

And, as a logical extension of the above question, what sort of options exist for the rear end? Or is dropping the R160 in favor of an R180/200 the only option to fit those extended gearsets? *prepares to cut up a 280ZX for its 4.11 R200 lsd* :grin:

 

legacy's didn't have front LSD. they had center, which is a whole different can of worms

 

the only factory 5-speeds with front LSD were JDM STis. but, there are more than a few aftermarket options for WRX etc. cheapest I've been able to find was about $300 for an OBX helical-type LSD.

 

this has nothing to do with the final drive. while the carrier is the same, and therefore the ring gears are the same (or similar enough to work), the pinion is different for the 4WD. I'm quite certain that the only way to change your final drive, is to use a legacy viscous center diff. but then you wouldn't have true 4WD.

 

as for the rear, only STis use an r180 rear end, so r160s in various gear ratios and LSD configs are out there. but if you go r200....you might as well get a locker!

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R160 FTW.

 

Many different LSD types avalible for it:

 

Kazz, Cusco, PG, and more for clutch type.

ATB-Quaife/Torsen/Helical for it as well.

SureTrac makes one, but its hard to find.

 

And more.

 

Gearing? everytihng from 3.545 to 4.444 was made with the R160.

 

R180: Maybe 4 LSDs avalible, and only 3.90 ratio could I find.

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Hi all.

 

I read allmost all the tread from the begining and I still don't understand how to swap my 1990 DL 1.8L 4WD 5 Spd. D/R 3.9 ratio front diff from regular to a lsd one...?

 

What parts do I have to change? From what Subaru can I take those parts?

 

In those pictures at the first massage, How can I see the difference between a lsd diff and non lsd diff? to me it looks the same, so where is lsd thing hiding?

 

Thanks, Gal.

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its just the front diff its self...the actuall differential.

 

No parts other than the diff its self need to be swapped.

 

You can order aftermarket, or get an OE STi 5spd front LSD from SUBARU-STi.

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From what year the STi have front LSD?

 

The STi have different ratio from my 3.9 4WD 5 Spd. D/R DL. Does it metter? Its not a source for a problems?

 

And from what year the front LSD STi diff will fit to my EA82 D/R 5 Spd. diff?

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