1jz with different diffs

[JustinGotA1j]

I'm looking for comments from all the guys who have done a 1jz swap and are using one of the american diffs and not the torsen. I am looking to swap in either a 3.73 gear set or a 3.91 gear set. I'm looking for all the pros and cons of each and any other information that anyone has to help me make a decision as to which diff will be better for my needs. My car is not going to be used for just track as it is my daily driver so I am ultimately looking for good cruising and also decent track performance. Thanks!

 

[annoyingrob]

Go with the 3.73 then. You'll have a lower cruising RPM for highway driving.

 

[FIL]

agreed... i've got a factory jza70 (came with the 4.11 torsen) and have blown 2 of the torsens now, finally have a 3.73 mechanical LSD (claimed to be a TRD 2 way, but havent pulled it apart to check) and I've been very happy with it...

Quarter mile time is slightly better with it, and it also means you won't need to change to 4th just before you cross the finish line...

And 3.73 is great for highway cruising too... the 1JZ doesn't have a problem launching on it at all...

 

[tlo86]

how did you blow the torsen?

 

[FIL]

first one went during a motorkhana on the local drag strip, launched off the line and it just locked up.... split some of the internal gears and locked itself solid...

second one i dropped the clutch at about 50kmh and it went bang... was able to drive it for a little bit, but didn't make it all the way home before the parts inside it locked it up...

not sure exactly what killed them, i wasn't doing anything particularly special when either of them let go....

 

[sctwinturbo]

Interesting

 

[JustinGotA1j]

Thanks for the replies everyone. My diff hasn't siezed up yet but its whining pretty good when I cruise around. Sounds like the 3.73 is what's going to be best for me. Does the american diff swap right in or will I need anything special to make it work? Thanks

 

[FIL]

if you swap the whole unit (ie including the casing) then it'll drop right in.... if you change the internals, you may need to get the half shafts to suit...

 

[Mischief7m]

just out of curiosity, before your diff's blew, did they whine all the time, or just when there is no load on the diff?
because mine whines only when there is no load on it, ie not accelerating, or using compression to break. but as soon as i throw it in neutral, it whines quite alot.
thanks,
trevor

 

[JustinGotA1j]

just out of curiosity, before your diff's blew, did they whine all the time, or just when there is no load on the diff?
because mine whines only when there is no load on it, ie not accelerating, or using compression to break. but as soon as i throw it in neutral, it whines quite alot.
thanks,
trevor

These are the same symptoms I am having minus the whining in neutral. Granted I don't roll around in neutral much to really know if it whines then.

 

[FIL]

ummm... mine didn't even whine at all.... they both behaved perfectly right up until they went bang... no backlash or anything...

 

[foreverpsycotic]

<3 the 4.30 with a BPU 1jz. Might ride a little higher, but getting to speed is so much more fun.

 

[Dylan JZ]

I honestly think the 3.73 is the best but not for BPU power, on the other hand I'm not a fan of the 4.3 craziness either. My 3.91 is what I consider the middle ground and the best, problem is theyre all old as hell.

 

[supramk3man]

3.73 is best the car i have now is a 1jz it came with the 4.10 it was to low. You was out of first before you had time to think. Went to 3.91 it was fun but still alittle to low in first. So finaly tried a 3.73 and love it. Car gets around 22mpg city and 28-30 highway if you keep out of boost and not speeding.

 

[tlo86]

i want a 4.3 instead of my 3.9 hehe its not a DD

 

[supramk3man]

i have a 4.30 lsd out of a 87 n/a if you need one pm me.

 

[tlo86]

i can get em locally didnt think it would be worth buying with shipping hehe

 

[supramk3man]

Agreed shipping can be high, some time people seem to have trouble finding the 4.30 that is lsd.

 

[macjac69]

Where were u 4 months ago?

 

[Jayhall]

Agreed shipping can be high, some time people seem to have trouble finding the 4.30 that is lsd.

well, if you know anyone with a 4.30 non lsd, ill have the carrier from mine for sale soon.