SM465 or SM420? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Chevy409 · 08-05-2002, 08:36 PM

I'm running a SM465 right now and love it off-road but on road, it's not much fun. The spread between 2nd and 3rd and 3rd and 4th is just too much if you're going to "hotrod" around town or something like that. Now, I've never ran a SM420 but the two trannies look nearly identical (cast iron, gears no chain, 4-speed) and I've heard the SM420 even holds up better, but how's the stretch between gears? Does it feel better than a SM465? Is first gear lower or higher? Any recommendations or info is much appreciated, thanks.

Blue_71 · 08-05-2002, 09:26 PM

first gear is lower (higher numirecly).. SM465 is 6.55:1, and SM420 is 7.02:1. im not sure about the gear spread though, because ive never even seen one, there harder then heck to find!

ChevLoRay · 08-05-2002, 10:03 PM

I ran an SM420 in my old '56 SWB 6-cyl 2WD (natch). The gear spread from the (granny) low to 2nd was huge! The 2-3 and 3-4 spreads weren't as wide, but this ain't no performance gearbox. You should IGNORE 1st, UNLESS you're doing some hellacious pulling, or need to get out and walk beside it while it is moving by itself.

If you want to shift gears, why not go to a late model 5-speed (Getrag) from an 88 and up? All synchro and overdrive, too.

CoryM · 08-05-2002, 10:46 PM

Dont forget the NP435. It has around a 4.5* 1st gear and the rest are spaced very well for a lower rear end. IMO it shifts much nicer than the 465 or 420 and I didnt break it in 2.5 years of very hard driving (the guys in chat will attest that I am hard on trannys

).
Happy Trucking.
CoryM

Chevy409 · 08-06-2002, 08:24 AM

ChevLoRoy, I'd rather a 5-speed but keep in mind, this is a 4x4 built for the woods so I still need some low gears. Also, would a most 5-speeds hold up to a big block? What about a NV4500?

CoryM, I don't think I've heard of a NP435, sounds cool though, First might be a little high for in the woods but I'll look into that. What year and make of a truck should I look to find one of those in?

Thanks

mikep · 08-06-2002, 08:33 AM

Ive got a NP435. As far as I know they only came behind big blocks. You can actually drive it normally. You know... 1st gear, second gear ....

Blue_71 · 08-06-2002, 01:47 PM

NV4500 has a 6.1ish first gear, 5 speed with granny and overdrive

CE20934 · 08-06-2002, 05:55 PM

The resto packet thing I got from Chevy lists the NP435CR as an option for six-bangers & V8s for '67.

Either way, I have that trans in my truck. Aside from a 1st that's too high for me (especially since I get stuck in traffic a lot & use the truck to haul things out of and into the weeds), it's a good trans. It survived seven months of no-clutch-shifting last year (I was in school at the time and had neither the time nor the cash to fix it).

I'm pretty sure it's factory. I just wish I had the build sheet or the glovebox sticker to confirm it.

**JIMs70GMC** · 08-06-2002, 08:50 PM

The SM465 and SM420 have the same 2nd and 3rd gear ratios, 3.58 and 1.70. The NP435 came in different versions in our trucks; with a 6.69 1st(73-80) or 4.56 1st(69-80) RPO codes M24 and M28. Only came in 2wds and not common. The NV4500 also 2 versions 6.34 1st(92-94) and 5.61 1st(94-up). Petersen's 4 wheel and off-road has a good article on the SM465 in their Aug 02 issue.

mikep · 08-06-2002, 09:03 PM

You might want to update that. Ive got a 4.56 first geared NP435 CR in my 68. Its the original tranny.

Chevy409 · 08-06-2002, 09:23 PM

Awesome, thanks for all the help everyone. After all that's been said and my own research I've been doing on the side, I'm beginning to believe the NP435 is a match for my needs (the one with the 6.69 1st gear). For those who have one, can you please give me a measurement when you get some spare time? Right now I've got the 409 backed by a SM465 and NP205, will a NP435 be a direct replacement or do i have to start moving mounts or getting special adapters and so on? Also, a couple last questions, bewteen the NP435 and NV4500, which is stronger and which will cost me the least amount of money to plant into my rig? Thanks again

Blue_71 · 08-06-2002, 10:42 PM

i think someone said the np435 is a 2wd case? the NV4500 will have to have some special stuff, because its a hydro clutch

*Fast68Chevy* · 08-07-2002, 02:30 AM

Ch465 was with a PTO on both sides of case ands the Sm420 was with onoly one PTO cover only on one side and reverse is toawrds driver side, and was 67 last year useage, 68 firs tyear useage for 465,

M28 435cr alot of the times only was avaialble behind the 350 engine per specs sheets info from these years GM data books,
would take all nmight to type out every detail of what trucks and what power combos that the C or CR N/P trannies could be ordered and what they were available with, all i can say is fat chance of finding one, they were verrry uncommonly ordered, id have o say 99% of all of them had the 420 or 465. if you want ot see if a CR oe was originally orderd in truck then look on the SPID label for M28 RPO code

--------------------
All available 67-72 4 speed (truck-only) tranny ratios per GM specs:

Warner T-10= 3.44, 2.28, 1.46, direct, 3.54 no power take off, N/A PTO RPM

SM420= 7.06, 3.58, 1.71, direct, 6.78 power on right side
425 PTO PRPM at 1000 engine RPM

CH465= 6.55, 3.58, 1.70, direct, 6.09 power on both sides, 425 PTO RPM at 1000 engine rpm

NP435C= 6.68. 3.34, 1.66, direct, 8.26 power on right side, 395 PTO RPM at 1000 engine RPM

NP435CR= 4.56. 2.28, 1.31, direct, 5.64 power on right side
also 396 PTO RPM at 1000 engine RPM

good luck

**JIMs70GMC** · 08-07-2002, 06:32 AM

I don't know if you want to do this but the NP435 was the 4 speed of choice in 70's F**ds, a friend of mine had one in his 79 4x4 with an NP205 TC.
mikep, this would not be the first time Jim Allen's book was wrong, he also listed the NP205 in 67 and 68 when the rockwell 221 was available. Oh well....

Chevy409 · 08-07-2002, 08:18 AM

Thanks for all the time guy.

JIMs70GMC, did your buddy have to do any fancy work or did it just slide right in there?

**JIMs70GMC** · 08-07-2002, 09:18 AM

The 79 was a F**d. I'm not even sure if the chevy 435 and F**d are interchangeable. I think the F**d NP205 hangs to the left as opposed to the Chevy that's on the right.

I know what you mean about on street performance, your not going to fly through the gears of an SM465. Personally it's something I'm going to live with. Your best bet would be an NV4500, I think several people at ColoradoK5 have done the swap. Have your granny gear and overdrive.

What's your gearing in your rearend? I have 4.10s and with 31" tires I can pull off in 3rd gear. Do you use 1st to start off or 2nd(while street driving)?

palallin · 08-07-2002, 10:22 AM

What are the glove box tag codes for the different trannies?

Chevy409 · 08-07-2002, 02:56 PM

I've got 3.08's with 33's and the low geared SM465 evens things out. Unless it's flat or slighty downhill, I usually start off in first. I guess my whole goal here is to have an off-road tranny that you could actually lay a patch of rubber with on the street (which I doubt I could do with the wide spread gears of my tranny right now). Fortunately, I spend most of my time in the woods but I'll look into the NV4500 swap, that sounds pretty sweet. Think it'll just bolt in? :p I'm guessing not.

**JIMs70GMC** · 08-07-2002, 03:15 PM

Get some 3.73 or 4.10 gears you'll have no problems spinning those tires in 2nd gear.

Chevy409 · 08-07-2002, 05:32 PM

I couldn't agree with you more Jim, it'll spin 'em in second now, no problem. But when the RPM's start to fly and it's time for 3rd, no way, the spread is too big to keep the tires burning.

08-05-2002, 08:36 PM	#1
Chevy409 Giddy up giddy up... Join Date: Feb 2001 Location: US Posts: 483	SM465 or SM420? I'm running a SM465 right now and love it off-road but on road, it's not much fun. The spread between 2nd and 3rd and 3rd and 4th is just too much if you're going to "hotrod" around town or something like that. Now, I've never ran a SM420 but the two trannies look nearly identical (cast iron, gears no chain, 4-speed) and I've heard the SM420 even holds up better, but how's the stretch between gears? Does it feel better than a SM465? Is first gear lower or higher? Any recommendations or info is much appreciated, thanks. __________________ 72 with 69 grille and custom 73-87 stepside. BIG BLOCK 409, SM465, NP205, 3/4 axles slung under a 5" lift, 3"bodylift, 112" frame, and 35inch Pro Comp X-terrains... "BUILT NOT BOUGHT" Here's the site...

08-05-2002, 10:03 PM	#3
ChevLoRay Old Skool Club Join Date: Jun 2001 Location: Benton, AR "The Heart of Arkansas" Posts: 10,880	I ran an SM420 in my old '56 SWB 6-cyl 2WD (natch). The gear spread from the (granny) low to 2nd was huge! The 2-3 and 3-4 spreads weren't as wide, but this ain't no performance gearbox. You should IGNORE 1st, UNLESS you're doing some hellacious pulling, or need to get out and walk beside it while it is moving by itself. If you want to shift gears, why not go to a late model 5-speed (Getrag) from an 88 and up? All synchro and overdrive, too. __________________ Member Nr. 2770 '96 GMC Sportside; 4.3/SLT - Daily driven....constantly needs washed. '69 C-10 SWB; 350/TH400 - in limbo The older I get, the better I was.

08-05-2002, 10:46 PM	#4
CoryM Registered User Join Date: Dec 1999 Location: Surrey, B.C. , Canada Posts: 874	Dont forget the NP435. It has around a 4.5* 1st gear and the rest are spaced very well for a lower rear end. IMO it shifts much nicer than the 465 or 420 and I didnt break it in 2.5 years of very hard driving (the guys in chat will attest that I am hard on trannys ). Happy Trucking. CoryM __________________ 1970 heavy duty C-10 fleetside sport truck. Vancouver B.C. Canada http://www.geocities.com/chevroletc1070 "Take up our quarrel with the foe: To you from failing hands we throw The torch; be yours to hold it high." Lieutenant Colonel John McCrae, Canadian Army

08-06-2002, 08:24 AM	#5
Chevy409 Giddy up giddy up... Join Date: Feb 2001 Location: US Posts: 483	thanks for the input ChevLoRoy, I'd rather a 5-speed but keep in mind, this is a 4x4 built for the woods so I still need some low gears. Also, would a most 5-speeds hold up to a big block? What about a NV4500? CoryM, I don't think I've heard of a NP435, sounds cool though, First might be a little high for in the woods but I'll look into that. What year and make of a truck should I look to find one of those in? Thanks __________________ 72 with 69 grille and custom 73-87 stepside. BIG BLOCK 409, SM465, NP205, 3/4 axles slung under a 5" lift, 3"bodylift, 112" frame, and 35inch Pro Comp X-terrains... "BUILT NOT BOUGHT" Here's the site...

08-06-2002, 08:33 AM	#6
mikep Used to have a truck Join Date: May 2002 Location: port orchard WA Posts: 1,552	Ive got a NP435. As far as I know they only came behind big blocks. You can actually drive it normally. You know... 1st gear, second gear .... __________________ No truck :-(

08-06-2002, 05:55 PM	#8
CE20934 Senior Member Join Date: Apr 2002 Location: Help! I'm in an office park with its own network of freeways! Posts: 470	The resto packet thing I got from Chevy lists the NP435CR as an option for six-bangers & V8s for '67. Either way, I have that trans in my truck. Aside from a 1st that's too high for me (especially since I get stuck in traffic a lot & use the truck to haul things out of and into the weeds), it's a good trans. It survived seven months of no-clutch-shifting last year (I was in school at the time and had neither the time nor the cash to fix it). I'm pretty sure it's factory. I just wish I had the build sheet or the glovebox sticker to confirm it. __________________ '67 C20--427 tall deck/SM420, 4.10 HO52 (Michigan has not been kind to the Old Man) '95 Caprice--355 LT1/T56/3.42 8.5" 10-bolt (daily driver, almost 300k on the chassis) '07 Outback--wife's car. 125k & counting. No head gasket or transmission issues yet. fingers crossed

08-06-2002, 08:50 PM	#9
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	The SM465 and SM420 have the same 2nd and 3rd gear ratios, 3.58 and 1.70. The NP435 came in different versions in our trucks; with a 6.69 1st(73-80) or 4.56 1st(69-80) RPO codes M24 and M28. Only came in 2wds and not common. The NV4500 also 2 versions 6.34 1st(92-94) and 5.61 1st(94-up). Petersen's 4 wheel and off-road has a good article on the SM465 in their Aug 02 issue. __________________ 1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs 1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX 1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears 1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now..... 1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone. 1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed. 1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm

08-06-2002, 09:03 PM	#10
mikep Used to have a truck Join Date: May 2002 Location: port orchard WA Posts: 1,552	You might want to update that. Ive got a 4.56 first geared NP435 CR in my 68. Its the original tranny. __________________ No truck :-(

08-06-2002, 09:23 PM	#11
Chevy409 Giddy up giddy up... Join Date: Feb 2001 Location: US Posts: 483	Awesome, thanks for all the help everyone. After all that's been said and my own research I've been doing on the side, I'm beginning to believe the NP435 is a match for my needs (the one with the 6.69 1st gear). For those who have one, can you please give me a measurement when you get some spare time? Right now I've got the 409 backed by a SM465 and NP205, will a NP435 be a direct replacement or do i have to start moving mounts or getting special adapters and so on? Also, a couple last questions, bewteen the NP435 and NV4500, which is stronger and which will cost me the least amount of money to plant into my rig? Thanks again __________________ 72 with 69 grille and custom 73-87 stepside. BIG BLOCK 409, SM465, NP205, 3/4 axles slung under a 5" lift, 3"bodylift, 112" frame, and 35inch Pro Comp X-terrains... "BUILT NOT BOUGHT" Here's the site...

08-07-2002, 02:30 AM	#13
Fast68Chevy Account Suspended Join Date: May 2000 Location: IL Posts: 0	Ch465 was with a PTO on both sides of case ands the Sm420 was with onoly one PTO cover only on one side and reverse is toawrds driver side, and was 67 last year useage, 68 firs tyear useage for 465, M28 435cr alot of the times only was avaialble behind the 350 engine per specs sheets info from these years GM data books, would take all nmight to type out every detail of what trucks and what power combos that the C or CR N/P trannies could be ordered and what they were available with, all i can say is fat chance of finding one, they were verrry uncommonly ordered, id have o say 99% of all of them had the 420 or 465. if you want ot see if a CR oe was originally orderd in truck then look on the SPID label for M28 RPO code -------------------- All available 67-72 4 speed (truck-only) tranny ratios per GM specs: Warner T-10= 3.44, 2.28, 1.46, direct, 3.54 no power take off, N/A PTO RPM SM420= 7.06, 3.58, 1.71, direct, 6.78 power on right side 425 PTO PRPM at 1000 engine RPM CH465= 6.55, 3.58, 1.70, direct, 6.09 power on both sides, 425 PTO RPM at 1000 engine rpm NP435C= 6.68. 3.34, 1.66, direct, 8.26 power on right side, 395 PTO RPM at 1000 engine RPM NP435CR= 4.56. 2.28, 1.31, direct, 5.64 power on right side also 396 PTO RPM at 1000 engine RPM good luck

08-07-2002, 06:32 AM	#14
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	I don't know if you want to do this but the NP435 was the 4 speed of choice in 70's F**ds, a friend of mine had one in his 79 4x4 with an NP205 TC. mikep, this would not be the first time Jim Allen's book was wrong, he also listed the NP205 in 67 and 68 when the rockwell 221 was available. Oh well.... __________________ 1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs 1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX 1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears 1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now..... 1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone. 1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed. 1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm

08-07-2002, 08:18 AM	#15
Chevy409 Giddy up giddy up... Join Date: Feb 2001 Location: US Posts: 483	Thanks for all the time guy. JIMs70GMC, did your buddy have to do any fancy work or did it just slide right in there? __________________ 72 with 69 grille and custom 73-87 stepside. BIG BLOCK 409, SM465, NP205, 3/4 axles slung under a 5" lift, 3"bodylift, 112" frame, and 35inch Pro Comp X-terrains... "BUILT NOT BOUGHT" Here's the site...

08-07-2002, 09:18 AM	#16
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	The 79 was a Fd. I'm not even sure if the chevy 435 and Fd are interchangeable. I think the F**d NP205 hangs to the left as opposed to the Chevy that's on the right. I know what you mean about on street performance, your not going to fly through the gears of an SM465. Personally it's something I'm going to live with. Your best bet would be an NV4500, I think several people at ColoradoK5 have done the swap. Have your granny gear and overdrive. What's your gearing in your rearend? I have 4.10s and with 31" tires I can pull off in 3rd gear. Do you use 1st to start off or 2nd(while street driving)? __________________ 1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs 1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX 1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears 1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now..... 1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone. 1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed. 1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm

08-07-2002, 10:22 AM	#17
palallin Registered User Join Date: Jul 2002 Location: St. James, MO Posts: 1,238	What are the glove box tag codes for the different trannies? __________________ '69 Longstep K-10: 327/SM465/T-221/Closed Knuckle Dana44/12-bolt.

08-07-2002, 02:56 PM	#18
Chevy409 Giddy up giddy up... Join Date: Feb 2001 Location: US Posts: 483	Jim... I've got 3.08's with 33's and the low geared SM465 evens things out. Unless it's flat or slighty downhill, I usually start off in first. I guess my whole goal here is to have an off-road tranny that you could actually lay a patch of rubber with on the street (which I doubt I could do with the wide spread gears of my tranny right now). Fortunately, I spend most of my time in the woods but I'll look into the NV4500 swap, that sounds pretty sweet. Think it'll just bolt in? :p I'm guessing not. __________________ 72 with 69 grille and custom 73-87 stepside. BIG BLOCK 409, SM465, NP205, 3/4 axles slung under a 5" lift, 3"bodylift, 112" frame, and 35inch Pro Comp X-terrains... "BUILT NOT BOUGHT" Here's the site...



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08-07-2002, 03:15 PM	#19
JIMs70GMC user # 2756 Join Date: Jun 2001 Location: Chesapeake, Virginia Posts: 4,612	Get some 3.73 or 4.10 gears you'll have no problems spinning those tires in 2nd gear. __________________ 1970 K25, 8' stepside bed 350/465/205 44 up front, 60 in the rear 4.10s rolling on 33" Dunlop MTs 1986 K5, 350/465/208 Dana 60/14 bolt from a cucv 36" Super Swampers TSL/SX 1983 K20 w/ CUCV axles, 350/700R4/208 sitting on 37" Goodyears 1986 M1031 6.2 diesel, TH400/NP205 locker in the rear and a LS in the front, all stock for now..... 1986 K30, 350/400/205 dana 60 and 14 bolt. I kept the drivetrain. Body/bad and chassis are gone. 1981 K30, 350/465/205 dana 60 and dually 14 bolt. Has a G80, and a flat bed. Going to replace the flat bed. 1985 K20, 350/400/208 10 bolt and SF 14 bolt. I wonder where I can find some 1 tons. Hmmmmm

08-07-2002, 05:32 PM	#20
Chevy409 Giddy up giddy up... Join Date: Feb 2001 Location: US Posts: 483	I couldn't agree with you more Jim, it'll spin 'em in second now, no problem. But when the RPM's start to fly and it's time for 3rd, no way, the spread is too big to keep the tires burning. __________________ 72 with 69 grille and custom 73-87 stepside. BIG BLOCK 409, SM465, NP205, 3/4 axles slung under a 5" lift, 3"bodylift, 112" frame, and 35inch Pro Comp X-terrains... "BUILT NOT BOUGHT" Here's the site...

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