T221 or NP208 with SM465 - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**americanmusc1e** · 06-24-2013, 11:14 PM

I'm really stuck on this and I need some expert opinions. I'm looking into driveline options for my '69 right now.

I have a 10-spline SM465 and Rockwell T221 that came with my '69 K20. I was tearing my SM465 down today and I found out that bearing that goes between the input and mainshaft looks really bad and the output is pretty worn. it really needs a mainshaft, input and a full rebuild. I haven't even looked at the Transfer case yet.

I also have a 32-spline SM465 and a NP208 out of my '82 K10 donor that donated the front axle and the lift. I haven't torn into the transmission or transfer case on it either yet. I'm going to try to do that tomorrow.

Now I'm stuck on which transfer case and transmission to use. The NP208 is a whole lot lighter and the low range is better, but the T221 is supposed to be practically indestructible and it will bolt right in and look original.

If you are wondering about my truck, it's a K20 frame with a 10b front axle and a 12b rear. 5" of lift, 3.73 gears. 35" tires and a 383 small block.

I'm not scared of fabricating a new transfer case crossmember. and I have the entire truck down to it's frame. I just want everyones opinion on which to use.

MitchFloyd · 06-25-2013, 09:45 AM

Well, if you decide to go NP208, let me know, I'd be interested in that T221!

Redcap · 06-25-2013, 10:02 AM

The T221 is a more durable unit.

dieseldude4bt · 06-25-2013, 12:01 PM

I run a t221, but the 208 has better low range and is easy to get parts for on road trips, try finding parts for a t221 broke down on the road. Even bearings are special order. I carry a spare on long road trips.

**americanmusc1e** · 06-25-2013, 01:21 PM

I know the t221 is much stronger, but I'm not sure if the np208 is going to be under that much stress. I guess my next step is to look at my other sm465 and see if it's any better
Posted via Mobile Device

**americanmusc1e** · 06-26-2013, 11:46 PM

Well to help the decision along, today I managed to score a 32-spline sm465 coupled to another np208 for $40. I'm gonna pull my 3 transmissions apart and then put them all together with whatever parts I need to build a good transmission. Then pull the two np208s apart and combine parts and keep the rest for spares
Posted via Mobile Device

06-24-2013, 11:14 PM	#1
americanmusc1e Senior Member Join Date: Jan 2009 Location: Austin, TX Posts: 1,079	T221 or NP208 with SM465 I'm really stuck on this and I need some expert opinions. I'm looking into driveline options for my '69 right now. I have a 10-spline SM465 and Rockwell T221 that came with my '69 K20. I was tearing my SM465 down today and I found out that bearing that goes between the input and mainshaft looks really bad and the output is pretty worn. it really needs a mainshaft, input and a full rebuild. I haven't even looked at the Transfer case yet. I also have a 32-spline SM465 and a NP208 out of my '82 K10 donor that donated the front axle and the lift. I haven't torn into the transmission or transfer case on it either yet. I'm going to try to do that tomorrow. Now I'm stuck on which transfer case and transmission to use. The NP208 is a whole lot lighter and the low range is better, but the T221 is supposed to be practically indestructible and it will bolt right in and look original. If you are wondering about my truck, it's a K20 frame with a 10b front axle and a 12b rear. 5" of lift, 3.73 gears. 35" tires and a 383 small block. I'm not scared of fabricating a new transfer case crossmember. and I have the entire truck down to it's frame. I just want everyones opinion on which to use. __________________ -- Josh Instagram: @americanmusc1e OLD SKOOL-- 1970 C10. 454/Th400/3.07 posi Build Thread FARM TRUCK----1949 Chevrolet 3800 Power Wagon Hauler Build Thread 1999 4wd OBS Tahoe - daily. DM me if you can't see photos i posted

06-25-2013, 09:45 AM	#2
MitchFloyd Registered User Join Date: Feb 2013 Location: Dallas, Tx Posts: 286	Re: T221 or NP208 with SM465 Well, if you decide to go NP208, let me know, I'd be interested in that T221! __________________ '62 Chevy K10

06-25-2013, 10:02 AM	#3
Redcap Registered User Join Date: May 2010 Location: Lewis County, WA Posts: 1,523	Re: T221 or NP208 with SM465 The T221 is a more durable unit. __________________ '77 K35 - 454, SM465/NP205, 4.56 D60/14bFF

06-25-2013, 12:01 PM	#4
dieseldude4bt Registered User Join Date: Mar 2011 Location: Co Posts: 412	Re: T221 or NP208 with SM465 I run a t221, but the 208 has better low range and is easy to get parts for on road trips, try finding parts for a t221 broke down on the road. Even bearings are special order. I carry a spare on long road trips. __________________ 63 k20 with cummins 4bt, owned sence 1982

06-25-2013, 01:21 PM	#5
americanmusc1e Senior Member Join Date: Jan 2009 Location: Austin, TX Posts: 1,079	Re: T221 or NP208 with SM465 I know the t221 is much stronger, but I'm not sure if the np208 is going to be under that much stress. I guess my next step is to look at my other sm465 and see if it's any better Posted via Mobile Device __________________ -- Josh Instagram: @americanmusc1e OLD SKOOL-- 1970 C10. 454/Th400/3.07 posi Build Thread FARM TRUCK----1949 Chevrolet 3800 Power Wagon Hauler Build Thread 1999 4wd OBS Tahoe - daily. DM me if you can't see photos i posted

06-26-2013, 11:46 PM	#6
americanmusc1e Senior Member Join Date: Jan 2009 Location: Austin, TX Posts: 1,079	Re: T221 or NP208 with SM465 Well to help the decision along, today I managed to score a 32-spline sm465 coupled to another np208 for $40. I'm gonna pull my 3 transmissions apart and then put them all together with whatever parts I need to build a good transmission. Then pull the two np208s apart and combine parts and keep the rest for spares Posted via Mobile Device __________________ -- Josh Instagram: @americanmusc1e OLD SKOOL-- 1970 C10. 454/Th400/3.07 posi Build Thread FARM TRUCK----1949 Chevrolet 3800 Power Wagon Hauler Build Thread 1999 4wd OBS Tahoe - daily. DM me if you can't see photos i posted



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