SR trans gearing

[UsedToOwn240SX]

Sup,

Been driving my redtopped 240 lately. I notice at around 70 mph, the RPM stays almost at 3500 RPM (5th gear). I recall when I had a 5-speed 1990 240, it would be around 3000 RPM at 70mph. This means SR trans is not exactly the same as that of KA, right? Does anybody has any info on the gearing (1st to 5th) on SR redtop transmission?

Thanks,

[Onizuka]

well, from what i heard, the KA and SR turbo trannies are the same, but the SR20DE (silvia Q's and J's and non turbo 180sx) trannies had shorter gears to make up for the lack of power. Since the turbo and non turbo SRs share the same block and transmission housing it is entirely posible that you got a non-turbo transmission with your motor.

[Altiman94]

it is a possibility but most likely this isn't the case. The gear ratios are the same in the sr20det and the ka, so your memory must be a little hazed

[UsedToOwn240SX]

Well, I just finished researching a bit on the S13 & S14 FSM (CA & SR available on the web) and compare it with my US 240SX FSM. All the gears are the same ratio, except for the overdrive 5th gear:1st 3.3212nd 1.9023rd 1.3084th 1.0005th .838 SR, .759 KA

I also did a little quick calculation, at 3000 RPM on 5th gear, the KA transmission results in 69 mph while the SR in 63 mph. Interesting.

[supreamS14]

Well, I just finished researching a bit on the S13 & S14 FSM (CA & SR available on the web) and compare it with my US 240SX FSM. All the gears are the same ratio, except for the overdrive 5th gear:1st 3.3212nd 1.9023rd 1.3084th 1.0005th .838 SR, .759 KAI also did a little quick calculation, at 3000 RPM on 5th gear, the KA transmission results in 69 mph while the SR in 63 mph. Interesting.

Yess! I was looking for this answer for about a year. I love frivolously using the search button! This should improve my highway gas millage a tad. If I was planing on drag racing and running trap speeds over 120MPH I would stick with the sr trans. But my trans has the dreadful bearing noise so now I will begin looking for a KA trans.

[kentuckyslider]

http://www.f-body.org/gears/

I use this gear calcutator when I changed from 3.91 J30 rear end to a 4.36 R32 rear. It is a very usefull tool for calculating top speed in each gear and how tire height effects your mph. I have 26" and 24.5" drag tires and a 3.91 and 4.36 R&P. Most of you have the stock 4.08 gears unless you've done something like me. I am know running the 3.91 gear and the 24.5"tires at the track. My 265/35/18 street tires are 25.3" tall. AS you can see their are many variables in calculating top speed in each gear... how high you rev it out, tire size, R&P gear and transmission gear. Don't forget if you don't have the stock tire height and 4.08 gear your speedo is wrong anyway!

[kentuckyslider]

Here is the top speed in each gear with my 3.91 R&P and my street tires.......

7500rpm redline

1st 43mph 2nd 76 3rd 110 4th 144 5th 190

I'm doing 70mph at 2750rpm in 5th and I get @5mpg better mileage with the KA transmission and the 3.91 then I did with the Sr transmission and the 4.36!