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Brad · 05-05-2003, 02:42 AM

I'm getting ready to do the LWB-SWB swap and when I do, I think I'm going to swap out my 3 speed for a 4 speed NP435 and go back to 3.07 in the rearend. I've included my final drive calculations and gear reduction for the swap and want to know what you all think.

Here are the gear ratios for the SM-318 3-speed, the SM-420 and NP-435-GA 4-speed transmissions.
Trans 1st 2nd 3rd 4th Rev
SM-318 2.94:1 1.68:1 1.00:1 ~-~ 2.94:1
SM-420 7.06:1 3.58:1 1.71:1 1.00:1 6.78:1
NP-435-GA 4.56:1 2.28:1 1.31:1 1.00:1 5.64:1

- (my percentages don't seem to match up in this post, but you get the idea)

SM318 --- 10.97 6.27 3.73
\ / \ /
57% 59%

NP435 ---- 14.00 7.00 4.02 3.07
\ / \ / \ /
50% 57% 76%

Also, see this related post:
Will NP435 work with 1 piece driveshaft

05-05-2003, 02:42 AM	#1
Brad Out of the carpool lane. Join Date: Jan 2000 Location: Clark Co, WA Posts: 5,672	Will this engine/tranny combo work ok? I'm getting ready to do the LWB-SWB swap and when I do, I think I'm going to swap out my 3 speed for a 4 speed NP435 and go back to 3.07 in the rearend. I've included my final drive calculations and gear reduction for the swap and want to know what you all think. Here are the gear ratios for the SM-318 3-speed, the SM-420 and NP-435-GA 4-speed transmissions. Trans 1st 2nd 3rd 4th Rev SM-318 2.94:1 1.68:1 1.00:1 ~-~ 2.94:1 SM-420 7.06:1 3.58:1 1.71:1 1.00:1 6.78:1 NP-435-GA 4.56:1 2.28:1 1.31:1 1.00:1 5.64:1 - (my percentages don't seem to match up in this post, but you get the idea) SM318 --- 10.97 6.27 3.73 \ / \ / 57% 59% NP435 ---- 14.00 7.00 4.02 3.07 \ / \ / \ / 50% 57% 76% Also, see this related post: Will NP435 work with 1 piece driveshaft __________________ 1968 C-10 SWB, 5.7 Vortec/700R4/3.73 posi, Torch Red 1968 Camaro, 250/Powerglide, all original (No, I'm not gonna drop a 350 in it!...Jeez!) 2000 Honda VFR in the faster yellow! 2008 Husqvarna TE-610 1967 C-10 SWB 'Six Appeal'-Gone but not forgotten... Last edited by Brad; 05-05-2003 at 02:45 AM.