So does anyone know the answer to this......I have a GSR trans with Quaife LSD, 4.78 final drive, and I'm turning 4000 revs at 70mph. Today I went to install the LS fifth gearset, and the gears coming out of the GSR trans are the exact same size as the new LS ones EXACT same size. So WTF? I would assume that the LS gears would be bigger than the GSR wouldn't they? Am I missing something or do I already have an LS fifth? And if I do have an LS fifth, then are my rpms so high @ 70 because of the 4.78?? Anyone know???

 

http://www.zealautowerks.com/transcalc.php

seems to me that with a gsr 5th you should be at 3850 approximately, and with the ls 5th you should be at 3500rpm with the 4.78 final drive.

 

Yeah, looks like it. Thanks for the link. So any idea why the gears coming off the trans are the same exact size as the LS ones that I just bought? That's where I'm starting to have doubts. I would have thought the LS gears would be bigger and then smaller to have a higher ratio?

 

Should I just go ahead and install the new gears and cross my fingers?? I'm all crossed up now. Anyone done this that can shed any light on the gears being the same size?

 

So I figured it out. The LS and GSR gears are essentially the same size. When you stick them end to end the first few teeth line up, but then gradually they become just slightly differently spaced out. It's so gradual that the mainshaft LS gear will actually engage with the countershaft GSR gear. But nonetheless it's a different ratio. Moral of this story is sometimes it's not a good idea to check your parts before you install them, just put them in and go!!

 

Good info, thanks for letting everyone know.

 

very good to know. i wish i had the skills to install an ls 5th thats for sure hahaha.

 

^Indeed. I'd be scared as **** to open the trans housing and just change gears all ***** nilly.

I'd probably put reverse in first somehow.

 

I could look up the part numbers, but do the LS and GSR trans use the same gear on the countershaft?
Not having the correct clearance can't be good, if the countershaft gear is a different size then the lash could be off and cause premature wear. I know people have done it, but if you're building a car to last 100k miles...

 

what year GSR tranny do you have? I have one from a 99 and on 80 mph, i'm at 4000 rpms. Seems like you have shorter gears somehow

 

i believe OP said he had a 4.78 final drive. I would assume that that's shorter than stock...

 

That's correct. It's 4.78, standard USDM GSR is 4.4!

The LS and GSR do NOT use the same countershaft gear, PN's are different.
LS main 23581-P80-000
LS counter 23461-P80-000
GSR main 23581-P80-V00
GSR counter 23461-P80-V00
That is why you MUST change both main and countershaft, which is what I did. I was just stating that the LS gear will engage the GSR gear. DO NOT RUN IT THAT WAY! I just checked because it was there. Plus I think some people are under the impression you only need one gear to do the conversion and they might just say OH it fits, I don't really need this other gear! So now the Main and Countershaft gear are correct for each other and the trans spins freely in all gears. I'm sure the lash is fine, I haven't checked of course, but I trust Honda!

As for being scared as **** to open the case.....the fifth gear cog is the outer most gear on each shaft, so it would be very hard to screw it up, let alone put reverse in there!!!
It should give me a drop of about 400 rpms! I'm not so worried about gaining gas mileage as I am reducing the racket that comes out of my 3" Vibrant exhaust!