Drivetrain AT/MT Drivetrain discussions on the 240sx and Silvia

can you swap ka and sr gears?

Old 05-20-2009, 02:50 PM
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Join Date: Jan 2006
Location: Long Island NY
Posts: 66
can you swap ka and sr gears?

Has anyone ever tried to regear a ka transmission with sr gears for better acceleration? I was just curious because I came across a post while surfing the internet that showed there is a difference between the gearing of the two. I also have read that the two transmissions are very similar, so it might be possible.

I am asking because I really don’t like the way third and fourth gear are in the ka tranny, and it would be great to get some better acceleration, by making them shorter. Here is the comparison that I found:

SR Tranny- ------------KA Tranny---
1st: -------------------1st:
15mph 3000rpms---------10mph 1900rpm
20 4500-----------------20 3600
30 6900-----------------30 4900
------------------------40 7500
40mph 4500rpms---------40mph 4300rpm
50 5700------------------50 5300
60 6800------------------60 6600
65 7300------------------70 6800

70mph 5300rpms---------60mph 4300rpm
80 6000------------------70 5100
90 6900------------------80 5900
100 7500-----------------90 6500
--------------------------100 7100
70mph 4000rpm-----------70mph 3800rpm
80 4500------------------80 4200
90 5000------------------90 4900
100 5500-----------------100 5300
110 6100-----------------110 6000

131mph 6000rpms---------80mph 3200rpm
--------------------------90 3600
--------------------------100 4000
--------------------------110 4400
--------------------------120 4900
--------------------------130 5300
--------------------------140 5600

I doubt the change would be huge or anything, but you could get some better acceleration with shorter gears, and if you have to rebuild your transmission and if they swap right in, why not? I just wanted to see if some one has tried this.

I also wanted to know if there was anyone that tried a taller 5th gear in the ka transmission. I would like to know if it is at all possible, to get a taller 5th gear from some other transmission because I think the one in there is to short. I know it would kill some of the acceleration, but I think it would be better to get some more highway mpg.

Optimally it would be the best to have a six gear transmission, but I don't know of any that I can get from a junkyard that would swap in without some major modifications.

Last edited by MasterOSkillio; 05-20-2009 at 02:58 PM. Reason: Sorry colums wouldn't line up with just spaces
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