NP 435. Anyone else got one?

[71ChevySS(straight6)]

So I figured out what transmission my '71 has in it, it's a New Process NP435. I looked it up, and evidently it's a pretty uncommon transmission? Limited to the 67-72 Chevy pickups?

My main question here is, would it be cheaper to put an overdrive on there, if one fits, change the gearing in the rearend, or just get a NV4500 to retrofit onto the 250? She's screamin' at 55 MPH. Thanks!

[Tx Firefighter]

I've had one GM NP435 transmission over the years.



It's very uncommon in GM trucks, but in a Fords, they are not rare at all. I never did get an answer as to why GM used the Muncie SM465 so much and the NP435 so little. FYI, my NP435 came out of a 71 GMC 3/4 ton.

[Wrenchbender Ret]

The NP235 came in a lot of GMC trucks back in those years. The Muncie was built by GM & the NP are built by Crysler. The early ones weren't very good. they had a weird syncro assembly that would break very often.

[SS Tim]

What are you running for gears? Stock 3.73 or the optional 4.11, maybe something else. What size tires do you have? Is your speedo accurate?

Do the numbers first to see what you have and then where you want to go.
http://www.summitracing.com/expertad...tio-calculator

Only then can you make an informed decision on what you can best afford for the return.

[71ChevySS(straight6)]

Originally Posted by SS Tim

What are you running for gears? Stock 3.73 or the optional 4.11, maybe something else. What size tires do you have? Is your speedo accurate?

Do the numbers first to see what you have and then where you want to go.
http://www.summitracing.com/expertad...tio-calculator

Only then can you make an informed decision on what you can best afford for the return.

I assume it has the 3.73s, but not positive. Not positive what size the tires are, but probably 27s (on 15" wheels). Fairly sure on the speedometer accuracy.

[SS Tim]

Originally Posted by 71ChevySS(straight6)

...My main question here is, would it be cheaper to put an overdrive on there, if one fits, change the gearing in the rearend, or just get a NV4500 to retrofit onto the 250? She's screamin' at 55 MPH. Thanks!

Originally Posted by 71ChevySS(straight6)

I assume it has the 3.73s, but not positive. Not positive what size the tires are, but probably 27s (on 15" wheels). Fairly sure on the speedometer accuracy.

Earlier trucks (67-69) actually offered a 3 speed+O/D manual transmission on the lower power C10s.
By your assumed answers its turning about 2500rpm, while fast by todays standards it was very normal for the time and ran the engine in an efficent powerband for a truck being used as a truck.

There are a couple of things to consider here. A close ratio trans. isn't really the problem, it just offers a closer gear spread so you are less likely to be too high or too low with a load.

If you change the rear ratio or tires to a taller effective ratio (lower numerically) the enige will turn slower for an given road speed however it also works against you at takeoff like a second gear start. But adding an O/D trans or an add-on O/D is expensive more so than than a regear or rear end swap.
But the good side is it gets you an additional gear (or more in the case of a Gear Vendors) so it starts of well and pulls nicely through the powerband. In fact with an O/D you might even want lower gears in back depending on what you actually have or plan to use for tires.

For a working towing truck a Ranger O/D in front of your NP435 is one solution.

An NV4500 or 3500 or even a rare MM7 (NP260?) four speed from the 80s are also possible mixing and matching parts and money.

If you are making this a simple fun truck and not intending on loading to GVW or higher all the time or trying to melt the tires off a T5 can work.
Jocko has outlined the swap for a 60-66 and many have used them in the later trucks as well.
http://67-72chevytrucks.com/vboard/s...d.php?t=482069

Consider where you are and where you want to go with the truck. Then how much a lower cruise RPM is worth to you. It takes a LONG time based on gas savings alone.
Powertrains are a balanced system and bad choices are an easy way to throw away money and/or alienate a supportive spouse.

[airdale94]

The NP435 came in the BBC Chevys and the GMC V-6 3/4 tons. Not sure about the 1/2 tons. The GM 435 is a close ratio trans., higher 1st and 3rd gears. While the Ford and Dodges 435 was a wide ratio, lower 1st and 3rd. The GM 435 has a 4.11 first gear ratio. While the SM465 has like a 6.5 (granny) ratio. Novac Industries has a rebuild kit for the 435s with a upgraded syncroniser design.

I would swap gears or rear end. What kind of truck do you have? I'm in the middle of a GM Corp. 14 bolt (73-87) swap for my 4.56 Eaton H052. I'll have a 3.21 gear ratio. With the right gears OD is not really needed. And the 4-speeds are a lot easier to rebuild.

TxFF- I "think" what GM was thinking was that with the big blocks and the V-6 the granny gear 465 was not needed, also the camper rigs could downshift sooner into 3rd when pulling uphill.

[kwmech]

I just took one out of my '68 (behind my 396) and put in a 465. It was starting to make lots of bearing noise. Thinking about rebuilding it, although I did not like the 4-1 first gear with the 3.54s

[Tx Firefighter]

Originally Posted by kwmech

I just took one out of my '68 (behind my 396) and put in a 465. It was starting to make lots of bearing noise. Thinking about rebuilding it, although I did not like the 4-1 first gear with the 3.54s

I rebuilt that one that I pictured above. It was real straightforward for me, and I'm in no means an experienced standard trans rebuilder. The kit was under 100 dollars. Normal tools and a manual I found on the Internet somewhere.

[1969_CM2590D]

My '69 3/4 ton GMC V-6 (CM2500) has a New Process NP435GL mated to a Spicer 60 full floater rear end with 4.11 gears. That was all you could get in this model, but there was an optional 4.56 gear set.

There are two NP435 in GM trucks. They are identical outside of gear ratios. The "close ratio" version has 4.56/2.28/1.31/1/5.64R gears. The bulldog/granny version has 6.68/3.34/1.66/1/8.26R. For '69 the suffixes were GA for the close ratio and GL for the creeper. CR and C were also used as suffixes, respectively.

Chevy and GMC had largely the same transmission and rear axle line up. The difference... if you told the Chevy dealer you wanted a granny four speed you got a corporate drivetrain- GM rear axle and SM465- anything else you had to ask for. Just the opposite with GMC, you got the NP435/Spicer, unless you asked for a cheaper combo- which would have been the Chevy's corporate setup.

I've driven SM465's and SM 420's and now I have the NP435GL. I like it best- it takes some getting used to shifting though. I (and I reckon many others) was used to big throws in a truck gearbox and I got a little paranoid when I first got my truck, an it seemed the shifter didn't want to engage the gears. I played with it in the driveway and found it has a narrow gate and has a sports car type action to it. Mine's quick and precise with a nifty "snick" movement. Very nice, not clumsy at all. Somewhere I read the it has an an action a BMW driver would be proud of and I'd have to agree.

The 435's seem to be desired by serious off-roaders- Broncos and Jeeps get the swap a lot. Don't quote me on this, but I heard that the NP gearbox was used on the flat fendered Power Wagons. The 4wd Dodges were tough in the postwar period, and the PW's reputation helped Dodge to rule the roost for many years when it came to full-size 4wd trucks. Flat fendered PW's aren't cheap but they are my top choice for 4wd- but I'd put a GMC V-6 in it...

[71ChevySS(straight6)]

Originally Posted by 1969_CM2590D

My '69 3/4 ton GMC V-6 (CM2500) has a New Process NP435GL mated to a Spicer 60 full floater rear end with 4.11 gears. That was all you could get in this model, but there was an optional 4.56 gear set.

There are two NP435 in GM trucks. They are identical outside of gear ratios. The "close ratio" version has 4.56/2.28/1.31/1/5.64R gears. The bulldog/granny version has 6.68/3.34/1.66/1/8.26R. For '69 the suffixes were GA for the close ratio and GL for the creeper. CR and C were also used as suffixes, respectively.

Chevy and GMC had largely the same transmission and rear axle line up. The difference... if you told the Chevy dealer you wanted a granny four speed you got a corporate drivetrain- GM rear axle and SM465- anything else you had to ask for. Just the opposite with GMC, you got the NP435/Spicer, unless you asked for a cheaper combo- which would have been the Chevy's corporate setup.

I've driven SM465's and SM 420's and now I have the NP435GL. I like it best- it takes some getting used to shifting though. I (and I reckon many others) was used to big throws in a truck gearbox and I got a little paranoid when I first got my truck, an it seemed the shifter didn't want to engage the gears. I played with it in the driveway and found it has a narrow gate and has a sports car type action to it. Mine's quick and precise with a nifty "snick" movement. Very nice, not clumsy at all. Somewhere I read the it has an an action a BMW driver would be proud of and I'd have to agree.

The 435's seem to be desired by serious off-roaders- Broncos and Jeeps get the swap a lot. Don't quote me on this, but I heard that the NP gearbox was used on the flat fendered Power Wagons. The 4wd Dodges were tough in the postwar period, and the PW's reputation helped Dodge to rule the roost for many years when it came to full-size 4wd trucks. Flat fendered PW's aren't cheap but they are my top choice for 4wd- but I'd put a GMC V-6 in it...

Wow! You really did your research! LOL! Now, what would make my truck move down the road easier? Could I just change the gearing in the rearend, or would an overdrive be cheaper and easier? Thanks!