4x4 sm420 to sm465 208 case - The 1947 - Present Chevrolet & GMC Truck Message Board Network

67ranchhand · 02-06-2019, 11:17 PM

Hello everyone, I have a 67 k10 with the sm420 and Rockwell case. I am going to drive this truck as much as I can. Maybe a daily driver. For reliability purposes and since the parts are hard to find for this trans and case, I was thinking about swapping it out with a 265/208 case. I have this trans in a square body with a cracked head 6.2 diesel. I would rather have the 205 but this is what I have. Has anyone done this swap? Is this a bolt in or are there modifications that need made? Driveshaft length? Mounting? Thanks guys!

sweetk30 · 02-06-2019, 11:31 PM

shafts more than likely yes need lengths changed .

floor shifter is different as the 208 unit bolts to the floor pan over the older rockwell/203/205 stuff just passing threw .

otherwise i dont know the rest as i am a auto trans guy .

**kwmech** · 02-07-2019, 02:25 AM

Grab all the parts from the square body from the bellhousing back. Modify the floor for the shifters and have the driveshafts rebuilt to length. Actually not bad of a swap since you already have all the parts available. The only thing that you may have to keep would be the clutch fork from the 67 into the aluminum bellhousing

Mike C · 02-09-2019, 08:23 PM

You will need the bellhousing form the square body as well. The SM420 has the smaller size bearing retainer. Same size as 3 speed and car 4 speeds while the SM465 is larger and needs bigger pilot hole.

67ranchhand · 02-11-2019, 08:29 PM

Thanks for all the reply's guys. When the weather breaks I will have to drag the old square out and do some investigating. Thanks again!

**Richard** · 02-11-2019, 10:43 PM

Should be pretty straight forward with all the parts you have. Would suggest converting the 208 to fixed yoke if needed as most Chevy 208's are slip yoke style.

sweetk30 · 02-12-2019, 06:59 PM

Quote:

Originally Posted by Richard

Should be pretty straight forward with all the parts you have. Would suggest converting the 208 to fixed yoke if needed as most Chevy 208's are slip yoke style.

no kits for this . its a half dodge and gm case to do it with some work involved .
if its a np241 then there is kits for that case .

67ranchhand · 02-12-2019, 10:38 PM

Thanks guys for the tip. I’m pretty sure it’s a 208 but won’t know for sure until I drag it out from its 6 year resting place! What is the advantage of the fixed yoke? To have a carrier bearing? Thanks again.

Brett

02-06-2019, 11:17 PM	#1
67ranchhand Registered User Join Date: Oct 2018 Location: Tiffin Ohio Posts: 74	4x4 sm420 to sm465 208 case Hello everyone, I have a 67 k10 with the sm420 and Rockwell case. I am going to drive this truck as much as I can. Maybe a daily driver. For reliability purposes and since the parts are hard to find for this trans and case, I was thinking about swapping it out with a 265/208 case. I have this trans in a square body with a cracked head 6.2 diesel. I would rather have the 205 but this is what I have. Has anyone done this swap? Is this a bolt in or are there modifications that need made? Driveshaft length? Mounting? Thanks guys!

02-06-2019, 11:31 PM	#2
sweetk30 Registered User Join Date: May 2012 Location: horseheads,ny rust belt Posts: 2,794	Re: 4x4 sm420 to sm465 208 case shafts more than likely yes need lengths changed . floor shifter is different as the 208 unit bolts to the floor pan over the older rockwell/203/205 stuff just passing threw . otherwise i dont know the rest as i am a auto trans guy . __________________ 77-k30lb BIG truck build . 87-k30lb budget beater build . 85-k30lb the plow machine build . 85-c10sb summer fun toy . ----------------------------- HOLLEY SNIPER efi = worst case of p.i.t.a i ever had . EDELBROCK pro flo 4 = best deal going so far . love my setup works great.

02-07-2019, 02:25 AM	#3
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,389	Re: 4x4 sm420 to sm465 208 case Grab all the parts from the square body from the bellhousing back. Modify the floor for the shifters and have the driveshafts rebuilt to length. Actually not bad of a swap since you already have all the parts available. The only thing that you may have to keep would be the clutch fork from the 67 into the aluminum bellhousing

02-09-2019, 08:23 PM	#4
Mike C Registered User Join Date: Dec 1999 Location: Austin, TX, USA Posts: 7,709	Re: 4x4 sm420 to sm465 208 case You will need the bellhousing form the square body as well. The SM420 has the smaller size bearing retainer. Same size as 3 speed and car 4 speeds while the SM465 is larger and needs bigger pilot hole. __________________ 44 Willys MB 52 M38A1 64 Corvette Coupe 68 Camaro 'vert LT1 & TH700 69 Z/28 355 12.6's @110 69 Chevy Short Step 4 1/2"/7" drop 72 Jimmy 4WD 4spd 4" & 35's 02 GMC 2500HD 4x4 Duramax

02-11-2019, 08:29 PM	#5
67ranchhand Registered User Join Date: Oct 2018 Location: Tiffin Ohio Posts: 74	Re: 4x4 sm420 to sm465 208 case Thanks for all the reply's guys. When the weather breaks I will have to drag the old square out and do some investigating. Thanks again!

02-11-2019, 10:43 PM	#6
Richard Senior Member Join Date: Dec 1999 Location: Southern California Posts: 2,695	Re: 4x4 sm420 to sm465 208 case Should be pretty straight forward with all the parts you have. Would suggest converting the 208 to fixed yoke if needed as most Chevy 208's are slip yoke style. __________________ Richard 1972 K10 Custom Deluxe SWB Fleetside My build https://67-72chevytrucks.com/vboard/...d.php?t=800746

02-12-2019, 10:38 PM	#8
67ranchhand Registered User Join Date: Oct 2018 Location: Tiffin Ohio Posts: 74	Re: 4x4 sm420 to sm465 208 case Thanks guys for the tip. I’m pretty sure it’s a 208 but won’t know for sure until I drag it out from its 6 year resting place! What is the advantage of the fixed yoke? To have a carrier bearing? Thanks again. Brett



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