NP440/MY6 (Chevy 4 Speed w/Overdrive) - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**HO455** · 07-12-2019, 03:37 PM

Is anyone familiar with this transmission? One for sale kinda local and I was wondering it it would be worth the trip north.

https://seattle.craigslist.org/sno/p...929681217.html

Ad reads as follows:
This is for an NP440 transmission that I recently rebuilt. Price is firm. This is a rare transmission used in some chevy trucks during the 80s. The chevy RPO code for this transmission is MY6. This is a chevy 4 speed with 4th gear being overdrive. There were two options for this transmission 4wd and 2wd. The 4wd transmissions got the cast iron case while the 2wd transmissions got an aluminum case. I took a 4wd case and converted it to 2wd with an aluminum tailshaft and 2wd mainshaft. This is the strongest way this transmission can be built in 2wd. I already have one of these in my car and I do not need this one. This transmission has a 27 spline output shaft tooth count and you can use a TH350 transmission crossmember to mount this transmission. This transmission uses a hybrid chevy chrysler bellhousing bolt pattern. This comes with the correct bellhousing. It also comes with a bellhousing to block spacer if you want to use a hydraulic throwout bearing. This transmission has almost the same gear ratios as a 700R4 transmission. If you want to keep a manual transmission and give your hotrod/truck overdrive that is decently strong and will not break the bank here is your chance.

NP440 Gear Ratios:
1st: 3.09
2nd: 1.67
3rd: 1.00
4th: 0.73

Input Shaft Spline: 10 Spline
Output Shaft Spline: 27 Spline
Flywheel Diameter: 11 inch flywheel will fit
Clutch Size: 11 inch clutch will fit
Speedometer Drive Gear: 17 Tooth Red Gear (Part #8640517)

**tkeduk8r** · 07-13-2019, 07:19 AM

They didnt make alot of these.... i have one for a future project and a spare for parts.... i have only ever seen three in junked trucks in the past 20 years. Its a muncie 4 speed look with od. If you trust the guy and his rebuild skills, id think about it, since the price of a rebuilt anything else is gonna be a fair amount more. Jmo.
Mike

**HO455** · 07-13-2019, 02:13 PM

Thanks for the Information. Now its decision time.

Tom · 07-16-2019, 06:01 PM

Theres like a 30 page discussion on these in the 73-87 forum. Everything you ever need to know.
They are a Chrysler transmission. They are fine with stock engines. They are not high performance units.

07-12-2019, 03:37 PM	#1
HO455 Post Whore Join Date: Feb 2016 Location: Portland Oregon Posts: 10,804	NP440/MY6 (Chevy 4 Speed w/Overdrive) Is anyone familiar with this transmission? One for sale kinda local and I was wondering it it would be worth the trip north. https://seattle.craigslist.org/sno/p...929681217.html Ad reads as follows: This is for an NP440 transmission that I recently rebuilt. Price is firm. This is a rare transmission used in some chevy trucks during the 80s. The chevy RPO code for this transmission is MY6. This is a chevy 4 speed with 4th gear being overdrive. There were two options for this transmission 4wd and 2wd. The 4wd transmissions got the cast iron case while the 2wd transmissions got an aluminum case. I took a 4wd case and converted it to 2wd with an aluminum tailshaft and 2wd mainshaft. This is the strongest way this transmission can be built in 2wd. I already have one of these in my car and I do not need this one. This transmission has a 27 spline output shaft tooth count and you can use a TH350 transmission crossmember to mount this transmission. This transmission uses a hybrid chevy chrysler bellhousing bolt pattern. This comes with the correct bellhousing. It also comes with a bellhousing to block spacer if you want to use a hydraulic throwout bearing. This transmission has almost the same gear ratios as a 700R4 transmission. If you want to keep a manual transmission and give your hotrod/truck overdrive that is decently strong and will not break the bank here is your chance. NP440 Gear Ratios: 1st: 3.09 2nd: 1.67 3rd: 1.00 4th: 0.73 Input Shaft Spline: 10 Spline Output Shaft Spline: 27 Spline Flywheel Diameter: 11 inch flywheel will fit Clutch Size: 11 inch clutch will fit Speedometer Drive Gear: 17 Tooth Red Gear (Part #8640517) __________________ Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. RIP Bob Parks. 1967 Burban the WMB,1991 S(stink)-10 Blazer,1969 GTO, 1970 Javelin, 1952 F2 Ford 4X4, 29 Model A, 72 Firebird. 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377

07-13-2019, 07:19 AM	#2
tkeduk8r Senior Member Join Date: Apr 2001 Location: Alexandria, MN Posts: 1,462	Re: NP440/MY6 (Chevy 4 Speed w/Overdrive) They didnt make alot of these.... i have one for a future project and a spare for parts.... i have only ever seen three in junked trucks in the past 20 years. Its a muncie 4 speed look with od. If you trust the guy and his rebuild skills, id think about it, since the price of a rebuilt anything else is gonna be a fair amount more. Jmo. Mike __________________ 63 C20 2WD, 230/SM420/4.11 73K 68 C30 dump truck, 327,SM425,4.56 66K original 68 C10 2WD SWB Stepper, 250/3-tree/3.73 66K.... Wifes 68 Buick Skylark Custom Conv., 350/TH400/2.56 In our family since '79 69 GMC 1500 SWB 2WD, 350/TH350/3.73 posi... 70 K10 SWB 4X4 4-sp,ps, pb, tilt, buckets, console, sliding back window (Need AC parts) WIP 72 Chevy K20 4x4 350/350/205/4.56 donor 72 Vette 350/M21/3.70 posi, triple black and super fast 84 Olds Cutlass Brougham 350/2004r/4.11 was Dad's

07-13-2019, 02:13 PM	#3
HO455 Post Whore Join Date: Feb 2016 Location: Portland Oregon Posts: 10,804	Re: NP440/MY6 (Chevy 4 Speed w/Overdrive) Thanks for the Information. Now its decision time. __________________ Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. RIP Bob Parks. 1967 Burban the WMB,1991 S(stink)-10 Blazer,1969 GTO, 1970 Javelin, 1952 F2 Ford 4X4, 29 Model A, 72 Firebird. 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377

07-16-2019, 06:01 PM	#4
Tom driving is in my blood Join Date: Dec 1999 Location: Mesa AZ Posts: 5,692	Re: NP440/MY6 (Chevy 4 Speed w/Overdrive) Theres like a 30 page discussion on these in the 73-87 forum. Everything you ever need to know. They are a Chrysler transmission. They are fine with stock engines. They are not high performance units. __________________ -78 c10 short/step: 388cid, M20, 5/5 drop, lots more. Playtoy and first vehicle. -98 c1500 x-cab: 5.7L, 17" rims, 5/6 drop, flowmaster, helper bags,NBS rear disk brakes. -02 Suburban 4x4: leveled front -CBR600F4i, CBR600RR, CBR1000RR, and standup skis DISCLAIMER: I cant spell for the life of me.



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