The Stovebolt Site Forums The Shop Area Driveline New Venture Transmissions, in a Stovebolt?

We hear a lot about using the T5 transmissions as an
overdrive replacement for the SM420 or three sp.
I've been driving a '97 GMC for about the last 12-14
years with it's 5speed manual trans and from what
I've been able to figure out it has a NV4500. I
really like that transmission. Unfortunately that
particular model has the bell housing cast into the
case so it is really not adaptable to anything else.
Looking at Novak's site and reading the description of
the NV4500 used in the Chevy and Chrysler trucks it
looks like that could be adapted for use with the
Stovebolts. Has anyone done any research into this
or read any thing about this possibility???

Denny Graham
Sandwich, IL

Several guys on the GMC site have used it. I think they used the Dodge one and it requires some machine work, I think to the front bearing cover. I'd try to look it up for you and get a link but you'd need to be a registered user to open the link.

From the specs at Novac's site it looks like the Dodge input
shaft is 1.125" longer than the SM420. That would be
a real problem. The GM NV4500 is only .125" longer.
Isn't that the same problem you have with the T5,
that is just a tad longer?
The case with the 5th gear extension is nearly twice as long as
the SM420. Wouldn't be a problem with a 3600 but might be with
a 3100. I don't have one to compare it to but you would need
about 20" from the bell housing to the output shaft.

Again, that is a sweet transmission, super smooth. Not to
popular with the off road guys because first isn't really a
rock climber gear like the SM420 or SM465.

It wouldn't be a surprise if there would be a few things that
would need some adaptation to install it. I can't find any info
on the front bearing retainer diameter, but I'd bet it would
take some machining or possibly even a custom one turned to
fit. It's really a heavy trans, looks to be a full 60# more than
the SM420.
dg

Bellhousing cast to case of transmission is the NV3500.

The NV4500 is a fairly straight forward swap. Shifter location is about 5.5 inches back of where an sm420 shift tower is. I use the 1994-1997 Dodge 2wd version in stovebolts. This transmission will bolt up with an adapter plate, and can be made to work with a Mechanical speedometer.

The Gm version of the NV4500 has no provisions to run a mechanical speedometer.

Advance Adapter sells an adapter plate that almost bolts to a stovebolt bellhousing. I say almost because the bolt pattern is correct, but the indexing hole is too large. Most stovebolts before 1967 have a bellhousing that is indexed to 4.686 inches. The AA plate is indexed to 5.125 inches. Either the indexing lip on the adapter plate will need to be turned down to 4.683 inches, or the bellhousing will need to be bored out to 5.125 inches.

If you get the dodge standard duty imput shaft, it is 10 spline on 1 1/8, just like a stovebolt clutch. If you get the heavy duty dodge version (diesel) it is 10 spline on 1 1/4 shaft. The shaft can be swapped out without getting into the transmission.

Both the heavy duty bearing retainer and the standard duty dodge bearing retainers are to big to fit in a gm throwout bearing. I took the standard duty bearing retainer, and spun it down on a lathe to match the sm 420 bearing retainer snout. About .060 needed to be removed... take your own measurements as I don't remember the exact numbers.

So the 94-97 dodge version can be mated to a stovebolt with an adapter plate, and most of the stock clutch components can be used. It is likely a custom pilot bearing/bushing will need to be made. The tip of the sm420 and many other gm transmissions is 0.590 inches. The dodge NV4500 has a tip of 0.750 inches. I just bore out a bronze oilite bushing to the desired size.

As far as gear ratios... the NV4500 from 1-4 lines up pretty closely with an sm420. The sm420 has a lower first gear ratio of 7.05:1 compared to 5.61:1 of the dodge NV4500. The NV4500 has a 0.73:1 5th or OD gear. The NV4500 is a popular swap in jeeps, land cruisers, fords, and gm wheelers, espeacially when it is used with a low ratio transfer caselike an Atlas. With 4.11 gears, and a 4:1 reduction in the transfer case, it is possible to achieve a crawl ratio of about 92:1. Of course that could be 115:1 or lower with 5.14 gears.

The NV4500 is a heavy transmission. It weighs in around 200 lbs dry. An sm420 is closer to 130 lbs.

Thanks for clearing the air Big. I'll add your reply to my
reference folder on these. Just out of curiosity, where did you
get your information from and it sounds like you have access to
a machine shop?
I just opened the door on the New Venture transmissions
yesterday and would like to know a little more about them. Been
gathering up as many articles as I have time for but it's like
putting a jigsaw puzzle together with all the variation.
The electronic speedo thing seems to be a problem with many of
the later transmissions that are available. That's just another
hurtle to be dealt with. Spline and drive shaft make up isn't a
problem as they can be made up any way you want them for not to
much money.
The input shaft on the Dodge 4500 is over an inch longer than
the SM420, is that the case with the 3500? Still not clear, but
the 3500 made for the GM and Dodge did have the bell housing
cast into the case is that correct?? I think I read where the
ones used in the Jeeps were bolted to the inline 6 bell housing.
I’ll bet they would be a little hard to find.
The shift tower setback was the first thing that I noticed
looking at the pix of the NV4500, don't know what the 3500
would be, but it doesn't look anywhere near as bad as with
the T-5's. I’ve seen some of them that have to have a goose
neck bent to get it out from under the seat almost. Even with
the seat full forward in my '50, the SM420 shifter tower is
at 11" so that wouldn’t be a problem with a NV4500.
Yep, turning a new pilot bushing and sizing the bearing retainer
is no problem, even if you had to make a whole new retainer.
The stumbling block I see is the extra length of the clutch
shaft on the Dodge’s. With that you would have to space it out
and I doubt if the mounting hole geometry is the same as the GM
design, so you’re talking about a complete adaptor plate to
space it out. AA didn’t seem to have anything for a Stovebolt
and their adaptors are pretty pricey. Thank the lordy I’ve got
a mill and lathe at my disposal and that I know how to use them.
Big difference between 7.03:1 and 5.61:1 when you're rock
crawlin’, even Novak says the guys shy away from them because
of that.
Yep, I think I posted earlier from the Novak site,
that the NV4500 weighed in at 195lb and SM420 at
135lb. Haven’t seen any specs on the NV3500, if you
find anything for that, appreciate you posting it here.

Denny Graham
Sandwich, IL

My 2004 jeep rubicon wrangler has the nv3500 in it from the factory. It also has the cast bellhousing.

I suppose you could use the nv3500 with a stovebolt 6 in a 1950 if you used the stovebolt to th350 adapter plate. At least the transmission would bolt to the engine. Clutch linkage would have to be figured because the hydraulic throwout. The nv3500 has a much higher 1 st gear than the nv4500. You would also need to figure out away to mount the engine in the chassis, as the bellhousing crossmember mount would be out.

AA has a plate for about $200 - 300, but as indicated either it or the bellhousing will need machining to work.

I have done this swap on my 59 gmc with pontiac v8. The beauty of the swap is it did not require new engine mounting geometry. Somewhere on oldgmctrucks.com there is a thread that has side by side pictures of the sm420 and the nv4500 from my swap. I have also made an adapter plate to do the swap on my 1940 gmc with 302 6 cylinder. That project is on the back burner for now.

When researching the swap I did use the Novac site as well as High- Impact. http://www.high-impact.net/nv4500.htm.

I really like the way the transmission shifts. I would reccomend the swap for working trucks in the 3/4 ton to 1 ton range, as well as 1/2 ton trucks with high power v8 engines. The only thing i might change would be the addition of a short throw shifter kit to make speed shifting easier. The nv4500 has long throws between gears, but the gates are way more defined than a sm420. The used transmission i purchased came out of a 1 ton dodge diesel with 250,000 miles. The transmission has not been rebuilt, and i have put an additional 80,000 miles on it. I have not been easy on the transmission.

Sounds like the NV3500 is out of the picture, but the NV4500 is
still in the running. Like the SM420, it sounds like it's
pretty much bullet proof. Wonder what the availability and
going price is for used ones in the junk yards????

Well it's somethin' to keep in mind, never know when I might
drift away from my preservationist beliefs and get the bug to
hack up a piece of history.

Tks
DG

Denny, don't go over to the dark side.... The forced is strong within you.

John

Gotta keep the old brain feed, never hurts to learn something
new John. I'm still a purist at heart, don't think I'm gonna
change a good thing, that being my stock '50 & '54, but you
don't know what might wonder into my yard somewhere down the
road. After all, I've still got 28 more years to play with
these old trucks.
As I posted earlier, my '97 GMC has the 5speed and I love it. I
do find my self reaching for fifth gear at times when I'm on
the highway with the old 216 screaming at three grand.

Denny G

Would the NV4500 work in a 10000 lb GMC 450. Meaning would it handle that weight with a 270 turning it. Sure would like to have overdrive, and Clark overdrive 5 speeds are real hard to find here. Thanks. Jim

AA has the gross vehicle weight of the transmission listed at 15,000 lbs. It also lists 450 lbs torque, which is way more torque than you can make from a 270.

So yes an NV4500 would make a good replacement for the Clark.