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j30 diff into ka pumpkin problem

4257 Views 10 Replies 4 Participants Last post by  1337240, 
supersayianjim2
well i thought that chucking the j30 pumpkin and stuffing the guts into the ka pumpkin would be easier and ideal. well the driveshafts to the j30 don't work. but the ka ones fit into the j30 diff..





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i used the j30 ring gear as i have a rb20 and i wan't that lower gear ratio to help with my turbo spool. the j teeth are a little taller than the ka's. i thought that would be an issue. but after some trial and error i got the spacer rings in the diff (in the same ka order). so iam thinking everything is fine..







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j30 on left ka on right.



now heres the problem. got everything mounted up.





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went to start the car(still on jackstands.) and i hear this when i drive it.. the gears also don't want to stay in 1st and 3rd. feels like the ds is poping them out..













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kinda hard to hear the whine over the sound of the car. but what do you guys think?? is it just the axels?? did i do a boo boo. or is the j30 not happy in it's new home??
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carps13guy
hmm, this is interesting. i am currently in the process of putting my shimmed vlsd back together. have you seen this write up? i have driven my friends cars before & after the shim & its a world of difference as far as lock up goes. you may want to do this before you totally put your diff back together

Shimming an R200 or J30 vlsd - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum
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supersayianjim2
interesting read. but i have a diff wine. i want to know is this normal after installing one in youre pumpkin??
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carps13guy
i would assume its the taller ring gear not properly meshing w/the other gear. some say that that happens when you shim a vlsd, but after the gears wear into each other it mellows out and goes away. are there a bunch of shavings in your gear oil?
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supersayianjim2
i didn't check as i didn't drain the gear oil. so i am running this

-s13 open diff front gear
-j30 diff
-s13 open axlels.

iam thinking because i didn't use the j30 front gear this is why this noise is happening..
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carps13guy
yeah, that would make sense
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supersayianjim2
but how long would the gears take to (mellow) into each other??
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carps13guy
ive tried searching & the only thing i could find is someone said it takes about 3 months of daily driving. but that was only 1 person.
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Briou
I put the j30 diff into my s13 pumpkin and swapped the ring gear and no problem....I did have to use the j30 output shafts and axles though and they fit after some trial and error....with out the J30 output shafts you only have an open diff...you need the one long and one short out put shafts to make the VLSD work properly.
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supersayianjim2
okay but since you swapped the ring gear didn't you still have a taller ka rear??

and if i swap the rear ring isn't the only thing iam changing is the lsd(vs open)??

id like to do both. get a lower gear(better for turbos) and an lsd. so is my only option getting another diff/pumpkin and using the j axels??
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1337240
my trans am(i know not nissan).
my brother stole it one night and blew the rearend.
i bought one from jegs(dont remember what one now gear wise.)
it still whines a lil bit.(its due to shimming) and i drive the car maybe 10 miles a month. so i dont worry about it. have put 15k on the rearend tho.(with pass's at a drag strip)
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