Changing the overdrive gear in a 1995 240sx 5spd

[jtk240]

1995 240sx KA24de 5spd base model

I have looked on the forums trying to find out if anyone has re-geared a 5spd to lower the rpm's while in overdrive.
Currently at 70 mph the rpm's are at 3000. I am wanting to try and find out if it is possible to change that gear to lower the rpm's to 2600 or so.
I am not sure if this is possible or has been done. I am hoping that someone can point me in the right direction on the stock gearing and if a different gear can be used.

Thanks

[zachattack_5491]

Never heard of that being done. You might be able to find the same type of gears in another Nissan transmission. I know very little about the insides of a transmission so I can't help there.

Why don't you just get a differential from a 300zx? Are you trying to avoid changing the ratios of all gears? That diff change would cost less than $200, changing transmission internals would require lots of research and I would imagine lots of cash.

[the converted]

The only direct swap gear is from the sr20 transmission, and would raise your revs in 5th. Other than that, your looking at custom parts ($$$$$).

[jtk240]

I never thought about using a 300z diff. I will have to look into the mounting and which year models.
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Converted ,
Thanks for your reply, I thought there may have been something other than going custom. Even the transmission guys I have talked to have said much the same thing.

[zachattack_5491]

Yeah it would be much easier and cheaper.

[Chaotic_Warlord]

When you say Overdrive are you talking about the actual overdrive on the automatic trans or are you referring to 5th gear on a manual? Either way gear ratio's are more defined at the differential, so just swap out to either a NA 300ZX diff or better yet the diff from a J30.

However if you are looking to modify the existing gearing in your trans there are some options albeit pricey ones. If you are dealing with the automatic trans look here - http://www.importperformancetrans.com/nissanauto.shtml

if you are dealing with the 5 speed manual you have a couple more options, one being that you can switch over to the 300Z trans which is not only beefier but also has more gear options. You could also attempt to swap in a 6 speed trans from the S15 SR, or you can drop in a S13/S14 SR trans (which is pretty much the exact same as the KA trans) but OS Giken has gears for the SR trans. Either route you take you're looking at an expensive modification unless you go with the stock gearing in the J30 or 300ZX diffs. You could also get an aftermarket diff and play with the gears that comes with it until you find a ratio you like.