67~91 4WD Manual Transmission I.D. Resource: SM420 SM465 SM330 NP440

[tarussell]

Figured it might help some folks if we had some info gathered in one place - also because there is so much misinformation out on the World Wide Web.

This thread is not meant to cover every single detail of these transmissions but rather some basic identification information that can be trusted.

As time permits I hope to have other identification resource threads to include auto transmissions, axles, differentials, adapters, transfer cases, CV-joints, crossmembers & braces - just to make searching a little easier.

These are pictures that I have gathered over the years and most are from the web and some are from CK5 so y'all might recognize a few of them as we go along.

Remember this only pertains to K/V-series GM trucks from 67~87/91 — and to keep it simple the “V” applications are referred to as “K”.

These are the four manual transmissions used in 4WD K series trucks from 1967~1991.
—————————————————

SM-420 Muncie 4-spd
1947~1967
Input torque rating:
Overall length -
Type of lubricants:
Weight -

Input shaft 1-1/8” 10-spline
Output shaft 10-spline

1st gear - 7.05:1
2nd gear - 3.57:1
3rd gear - 1.70:1
4th gear - 1:1
Reverse - 6.78:1

Shift pattern:






——————————————————


SM-465 (CH-465) RPO M20
Muncie 4-spd
1968~1991

Input shaft 1-1/8” 10-spline
Output shaft:
68~80 K5,10,20 10-spline
81~91 K5,10,20 32-spline
77~84 K30 10-spline
85~91 K30 32-spline

1st gear - 6.55:1
2nd gear - 3.58:1
3rd gear - 1.70:1
4th gear - 1:1
Reverse - 6.09:1

Shift pattern:

Note: The SM465 ( CH465 ) was used in the 88~91 GMT400 trucks as well but had a different aluminum top cover with the shifter tower moved to the rear to accommodate the new truck interior design.

——————————————————

SM-330 H.D. RPO ZW4
Muncie 3-spd
67~81

Input shaft 1-1/8” 10-spline
Output shaft 27-spline

1st gear 3.17:1
2nd gear 1.75:1
3rd gear 1:1
Reverse 3.76:1

Shift pattern:




——————————————————

NP-440 RPO MY6
New Process
4-spd O/D
Note: Based off of the NP833 ( same 4-spd used in MOPAR 440-6 & 426-HEMI’s ) but modified gear ratios with an overdrive for GM trucks made with a cast iron case instead of aluminum.

81~87
Input shaft 1-1/8” 10-spline
Output shaft 27-spline

1st gear - 3.09:1
2nd gear - 1.67:1
3rd gear - 1:1
4th gear - .73:1 O/D
Reverse - 3:1

Shift pattern:














Please add to the discussion of these transmissions of this time frame so we all can benefit and collaborate and collect good accurate data together.

Hope this is help for any fellow CK5’r in need and helps to keep CK5 a reliable resource.

Tom

 

[ZooMad75]

Nice detail. I’d add a suggestion to add the popular nv4500 to the detail since it’s a common swap to gain overdrive over the SM465. Sizing matches up to the 465 pretty close too.

The 465 also was used in the early gmt400 trucks if anybody was looking to find one it just widens the search net.

 

[tarussell]

Nice detail. I’d add a suggestion to add the popular nv4500 to the detail since it’s a common swap to gain overdrive over the SM465. Sizing matches up to the 465 pretty close too.

The 465 also was used in the early gmt400 trucks if anybody was looking to find one it just widens the search net.

Good idea - I’ll work on that tonight and update it.

 

[ZooMad75]

Good idea - I’ll work on that tonight and update it.

See Larry’s posts on his burb build as well as mine. He’s got good pics of them with measurements comparing lengths to the 465.

 

[USSkoval]

The 3-speed, column shifted unit I think is rare as hen's teeth.

As for the overdrive 4-speed, the 2wd units tended to have an aluminum case, but I'm 99% sure I remember reading about at least one 4x4 version that wound up with an aluminum case as well. Have you heard anything about those or am I delirious?

 

[tarussell]

Thanks to ZooMad75 suggestion of adding a little information on the NVG4500 or NV4500 because it is a popular addition/upgrade to the older GM trucks here’s an addition to the manual transmission thread.

NV/NVG-4500 RPO MT8 & MW3
H.D. 5-spd w/ granny low & O/D
91~07 ( 91 was GMT400 only )

91~93 1st & reverse gears were not synchronized.

GM Input shaft 1-1/8” 10-spline

Note: there are a few variations as this transmission was shared with Dodge gas & diesel engines and upgraded over the years of production - there’s even an aftermarket upgrade 1-3/8” input shaft for the later 5.61:1 gear set!

GM Output shaft 32-spline

Note: All GM 4WD’s used the 32-spline shaft but Dodge used 23 & 29 splined shafts.

92~94 gear ratios:
1st gear - 6.34:1
2nd gear - 3.44:1
3rd gear - 1.71:1
4th gear - 1:1
5th gear - .73:1 O/D
Reverse - 6.24:1



95~07 gear ratio changes
Note: The 95 model seems to be on its own as there were internal ratio changes made but not the case to bellhousing bolt pattern that followed in 96 along with the index bore increase and provisions for a different hydraulic T.O.B. setup.

1st gear - 5.61:1
2nd gear - 3.04:1
3rd gear - 1.67:1
4th gear - 1:1
5th gear - .75:1 O/D
Reverse - 5.04:1

Shift pattern:








There’s even a cast iron tail housing made to fit a NP-205 ( note the cutout for the shift rail )


Early bellhousing


Late bellhousing


The following pics are from either LARRY or ZooMad75’s ( I’ve gone through so many pics gathering information for this that I can’t keep up with what pic belongs to who ) builds of a NVG-4500 in an ole Square truck

If a STRONG O/D transmission is what you’re after that is close in size as a SM-465 then a NVG-4500 is the ticket.

 

[tarussell]

See Larry’s posts on his burb build as well as mine. He’s got good pics of them with measurements comparing lengths to the 465.

If possible would you add a link to yours and Larry’s build threads ( I’m having trouble getting the links to work ) as they are a great read and resource for this information.

Thanks!

 

[tarussell]

The 3-speed, column shifted unit I think is rare as hen's teeth.

As for the overdrive 4-speed, the 2wd units tended to have an aluminum case, but I'm 99% sure I remember reading about at least one 4x4 version that wound up with an aluminum case as well. Have you heard anything about those or am I delirious?

Yes, the 4WD’s were cast iron and the 2WD’s were aluminum but it’s possible that they put some aluminum cases in the 4WD’s at some point ?
The few that I worked on back in the day were iron on the 4x4’s and aluminum on the 2WD’s but I think I only saw one of each.

It seems the old MOPAR hotrod guys are after the GM iron cases for drag racing - makes for a nice upgrade for less case deflection.


As for the 3-spd 4WD Squares I absolutely agree - they are most definitely rare!
They stopped putting them in the 4WD’s in 1981 but there was still a 3-spd still offered ( a slightly different variant but not the SM-330 ) in the 2WD’s ( mostly in-line 250’s thru ‘84 and the 4.3 V-6’s from ‘85~’87 ).

 

[tarussell]

The 3-speed, column shifted unit I think is rare as hen's teeth.

As for the overdrive 4-speed, the 2wd units tended to have an aluminum case, but I'm 99% sure I remember reading about at least one 4x4 version that wound up with an aluminum case as well. Have you heard anything about those or am I delirious?

Ya might have noticed the pic that I used to show the guts of the NP-440 is an aluminum version - could not find a decent pic of a cast iron version with the shift cover off.

 

[USSkoval]

Ya might have noticed the pic that I used to show the guts of the NP-440 is an aluminum version - could not find a decent pic of a cast iron version with the shift cover off.

Nope, I didn't even notice lol. Are there any major differences between the two cases? I've got a couple of the 4x4 versions and can open one up.

 

[tarussell]

Nope, I didn't even notice lol. Are there any major differences between the two cases? I've got a couple of the 4x4 versions and can open one up.

Not that I know of but I’ve never compared the two side by side.

I think the tail shaft is common between the two just because of the length of the adapter but I’ve never measured either one.

The trans is actually a fairly strong unit ( not compared to the level of the 465 ) due to the distance between the main shaft and counter gear set.
It was a decent attempt to offer an O/D transmission in the early days of overdrives - I guess GM realized that the BW T-5 wasn’t gonna cut it in a full-size truck.

 

[ZooMad75]

If possible would you add a link to yours and Larry’s build threads ( I’m having trouble getting the links to work ) as they are a great read and resource for this information.

Thanks!

I’ll run through it tonight.

 

[Fastereddie]

Just as an fyi for anyone looking those pics above of nv4500’s are dodge units. You can tell from the extension housing. The dodge has a single rib on top and the gm has a double rib.

 

[tarussell]

Just as an fyi for anyone looking those pics above of nv4500’s are dodge units. You can tell from the extension housing. The dodge has a single rib on top and the gm has a double rib.
View attachment 497368

Very good to know !
I searched for quality pics and assumed that that the 4WD extension housings were common between both versions.

Great pic - please share more if ya got them or post a link to a build for reference.

 

[ZooMad75]

IIRC the bell housing flange to case mount flange is basically the same between a nv4500 and sm465 with the tcase adapter in place. I’ll find Larry’s pics that show that.

It’s also within 1/2” or less to the bell housing flange to t case flange on the adapter for a 700r4 also. My 4500 basically dropped right in where my 700r4 came out without moving the t-case cross member.

It’s almost like GM engineers planned it to fit.

 

[imiceman44]

Thanks to ZooMad75 suggestion of adding a little information on the NVG4500 or NV4500 because it is a popular addition/upgrade to the older GM trucks here’s an addition to the manual transmission thread.

NV/NVG-4500 RPO MT8 & MW3
H.D. 5-spd w/ granny low & O/D
92~07

GM Input shaft 1-1/8” 10-spline

Note: there are a few variations as this transmission was shared with Dodge gas & diesel engines and upgraded over the years of production - there’s even an aftermarket upgrade 1-3/8” input shaft for the later 5.61:1 gear set!

GM Output shaft 32-spline

Note: All GM 4WD’s used the 32-spline shaft but Dodge used 23 & 29 splined shafts.

92~94 gear ratios:
1st gear - 6.34:1
2nd gear - 3.44:1
3rd gear - 1.71:1
4th gear - 1:1
5th gear - .73:1 O/D
Reverse - 6.24:1



95~07 gear ratio changes
Note: The 95 model seems to be on its own as there were internal ratio changes made but not the case to bellhousing bolt pattern that followed in 96 along with the index bore increase and provisions for a different hydraulic T.O.B. setup.

1st gear - 5.61:1
2nd gear - 3.04:1
3rd gear - 1.67:1
4th gear - 1:1
5th gear - .75:1 O/D
Reverse - 5.04:1

Shift pattern:
View attachment 497354


View attachment 497355
View attachment 497356
View attachment 497358
View attachment 497359
View attachment 497360
There’s even a cast iron tail housing made to fit a NP-205 ( note the cutout for the shift rail )
View attachment 497361

Early bellhousing
View attachment 497364

Late bellhousing
View attachment 497365

The following pics are from either LARRY or ZooMad75’s ( I’ve gone through so many pics gathering information for this that I can’t keep up with what pic belongs to who ) builds of a NVG-4500 in an ole Square truck

If a STRONG O/D transmission is what you’re after that is close in size as a SM-465 then a NVG-4500 is the ticket.

View attachment 497357

View attachment 497362

View attachment 497363

One correction, nv4500 was offered from 91, not 92.
I have a few 91 to corroborate what I found online

 

[imiceman44]

Another thing I couldn't corroborate is 1991-1993 had no synchro on 1st and reverse.

 

[tarussell]

One correction, nv4500 was offered from 91, not 92.
I have a few 91 to corroborate what I found online

While researching information ( I’m very familiar with the ole 4500 but not as good as the true Square transmissions ) to make sure my memory hasn’t faded I found that it stated that 1991 was the first year as well.
I was worried that either that was a mistake or that it was ready in 1991 but wasn’t used for production until 1992 - so I’m assuming these 1991’s were GMT400 trucks only just to be clear for folks researching this stuff?
I’ll update the year offering range span on the info post - appreciate the correction.

 

[tarussell]

Another thing I couldn't corroborate is 1991-1993 had no synchro on 1st and reverse.

Yeah, I was battling of how much details needed to be given but that seems note worthy enough to include - good call.

 

[tarussell]

IIRC the bell housing flange to case mount flange is basically the same between a nv4500 and sm465 with the tcase adapter in place. I’ll find Larry’s pics that show that.

It’s also within 1/2” or less to the bell housing flange to t case flange on the adapter for a 700r4 also. My 4500 basically dropped right in where my 700r4 came out without moving the t-case cross member.

It’s almost like GM engineers planned it to fit.

There could be some actual truth to that considering that in 1985 GM made the effort to match the dimensions ( at least for the front driveshafts ) of all tranny options via the adapters and foot mount locations - they may have determined the 4500’s tail shaft length and mount location by what was already in production and most of those adapters were common dimensions from the last of the square adapters.
Good stuff !