250 i6 mated to a muncie m21 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

stringbean25 · 02-25-2009, 02:21 PM

i have a 68 c-10 long-bed w/ 250 and sm465 its my first chevy truck. I really dig the little straight six and have been doing a lot of research on it to get power from it, but i don't like the trans that's in it at the moment i want to keep it a manual does anyone have some info they'd like to share on what i need to make a muncie m21 or 22 work

primered_junk · 02-25-2009, 04:03 PM

Remove the granny tranny, and bolt in the M-21. You'll need a different drive shaft and shifter. Most of the M-21 units had a TH400 driveshaft yolk. The stock cross member mounted bell housing clutch etc will work. I've done it before, the biggest problem is the shifter. Most affordable 4 speed shifters are way too short and your knuckles will drag the floor. I would also add some form of a rear cross member for added support, the stock bell housing mounts will work fine, I just don't like the idea of a high dollar Muncie hanging out in the open.

stringbean25 · 02-25-2009, 04:24 PM

thanks for the info this will be my first trans swap the main concerns were the bell housing bolt pattern mating to the trans it self, the input shaft, clutch & fly-wheel, the rest i figured wouldnt be to bad to get to work.

do you have anyother concerns? i should look for

primered_junk · 02-25-2009, 04:58 PM

I'd make sure the throw out bearing is new, and double check the rest of the clutch. Spend your money on a quality shifter, you can get a mechanism from hurst fairly affordable, then choose a handle that fits your truck and arm length. I used the universal indy 4 speed shifter in mine. The indy is affordable, and you can still order a stick that fits. Shifter pn 5030030, and browse the catalog at your local speed shop for the handle of your choice. Finding a drive shaft can also be a pain, I used one out of an automatic truck, if I remember I had to shorten in a bit, but can't really recall. If you can fabricate you can shorten it, or your local drive line shop can do it, around here it's about a hundred dollar bill. I would also recommend re-sealing the trans, and new u joints and a pinion seal on the diff if needed. It is really alot easier than it sounds, about 3 hours worth of work, that included massaging the shifter hole to fit the side loaded stick. Hope this helps and does not confuse you.

stringbean25 · 02-25-2009, 05:20 PM

cool thanks again

like you said it seems to be easier than i thought so now im gona start my quest for a trans swap

02-25-2009, 02:21 PM	#1
stringbean25 Registered User Join Date: Feb 2009 Location: denver colorado Posts: 6	250 i6 mated to a muncie m21 i have a 68 c-10 long-bed w/ 250 and sm465 its my first chevy truck. I really dig the little straight six and have been doing a lot of research on it to get power from it, but i don't like the trans that's in it at the moment i want to keep it a manual does anyone have some info they'd like to share on what i need to make a muncie m21 or 22 work

02-25-2009, 04:03 PM	#2
primered_junk ASE master tech/machinist Join Date: May 2008 Location: Blue Mound Texas Posts: 303	Re: 250 i6 mated to a muncie m21 Remove the granny tranny, and bolt in the M-21. You'll need a different drive shaft and shifter. Most of the M-21 units had a TH400 driveshaft yolk. The stock cross member mounted bell housing clutch etc will work. I've done it before, the biggest problem is the shifter. Most affordable 4 speed shifters are way too short and your knuckles will drag the floor. I would also add some form of a rear cross member for added support, the stock bell housing mounts will work fine, I just don't like the idea of a high dollar Muncie hanging out in the open. __________________ "I sit here and I pray in my broken down Chevrolet....."

02-25-2009, 04:24 PM	#3
stringbean25 Registered User Join Date: Feb 2009 Location: denver colorado Posts: 6	Re: 250 i6 mated to a muncie m21 thanks for the info this will be my first trans swap the main concerns were the bell housing bolt pattern mating to the trans it self, the input shaft, clutch & fly-wheel, the rest i figured wouldnt be to bad to get to work. do you have anyother concerns? i should look for

02-25-2009, 04:58 PM	#4
primered_junk ASE master tech/machinist Join Date: May 2008 Location: Blue Mound Texas Posts: 303	Re: 250 i6 mated to a muncie m21 I'd make sure the throw out bearing is new, and double check the rest of the clutch. Spend your money on a quality shifter, you can get a mechanism from hurst fairly affordable, then choose a handle that fits your truck and arm length. I used the universal indy 4 speed shifter in mine. The indy is affordable, and you can still order a stick that fits. Shifter pn 5030030, and browse the catalog at your local speed shop for the handle of your choice. Finding a drive shaft can also be a pain, I used one out of an automatic truck, if I remember I had to shorten in a bit, but can't really recall. If you can fabricate you can shorten it, or your local drive line shop can do it, around here it's about a hundred dollar bill. I would also recommend re-sealing the trans, and new u joints and a pinion seal on the diff if needed. It is really alot easier than it sounds, about 3 hours worth of work, that included massaging the shifter hole to fit the side loaded stick. Hope this helps and does not confuse you. __________________ "I sit here and I pray in my broken down Chevrolet....."

02-25-2009, 05:20 PM	#5
stringbean25 Registered User Join Date: Feb 2009 Location: denver colorado Posts: 6	Re: 250 i6 mated to a muncie m21 cool thanks again like you said it seems to be easier than i thought so now im gona start my quest for a trans swap



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