#5: The New Venture NV4500 (a.k.a. NVG4500)

The NV4500 was released in GM trucks in 1993 (Dodge versions in 1995) through a joint-venture between General Motors and Chrysler Corporation, thus forming the New Venture Company (a naming derivative of Chrysler’s New Process division, and GM’s Stewart / Muncie division). While some may argue that the NV4500 was born from Chrysler’s 1972 NP4500, this is far from the truth as there are few similarities between them.

The NV4500 barely made our list of favorite manual transmissions. Once, many moons ago, several of our media brethren latched onto this transmission and even touted it as the “holy grail” of manual transmission conversions for dedicated off-roaders looking for a decent low range coupled with overdrive, but as time ticked on, they were proven quite wrong.

We’ll try not to be too hard on the NV4500 as it is one of the better manual transmission, but it is plagued with long-term fatigue and failure problems, many of which are due to inadequate mainshaft clutch splines, and counter shaft bearing failures. Conceptually speaking, this transmission is better suited for short-to-medium sized 4×4’s with moderately powered engines, as a heavy, full-size rig coupled with big horsepower will certainly put this tranny into an early grave. However, this is where conception and reality collide – The NV4500 is nearly twice as long as the rest of the manual transmissions on our list, which may make it difficult for the Jeep CJ5’s, FJ40’s, Sammies and other short wheel base rigs to give it a good home.

The NV4500 has an attractive low-range gear (5.6:1) and an overdrive, but its strength as compared to other 4-speed manual transmissions with torquey motors, is inferior. Lets face it, overdrive isn’t all that attractive in a manual transmission when you’re dealing with oversized tires, and a rig that sees less highway miles than a golf cart.

• What we like: Deep first gear (5.61:1). Overdrive. Dual PTO ports. Capable of handling 460 lb./ft. of torque. Older GM version could be found with a 6.34:1 low-range gear ratio.
• What we don’t like: Insanely long (20.4″). Weak mainshaft clutch splines. Can’t take big horsepower / torquey engines.
• What it came in / When it was available: The NV4500 can be found in GM trucks (3/4 and 1 ton versions) from 1993 and up, and Dodge trucks (3/4 and 1 ton versions) from 1995 and up.
• Identification: The NV4500 should be relatively easy to recognize due to it’s 20″ plus length. It’s a cast-iron body with aluminum top plate, and an aluminum 4X4 adapter housing. Dual PTO plates on either side of the transmission make it remarkable, as do the copious ribbing.
• • Make: New Venture Gear
  • Weight: 195 lbs.
  • Case: Cast iron (w/ aluminum top and aluminum rear)

#4: The GM / Muncie SM465 (a.k.a. CH-465 or CH465)

Consider the SM465 the SM420 sibling that grew up and made something for himself. Not unlike the SM420, the 465 sports a very low 1st gear (6.55:1), with far better off-road manners – such as easier shifting. This was also one of the longer-running work-horse standard transmissions for GM, which started production in 1968 and ended in 1991. There were three iterations to this gearbox, but there were really no drastic improvements or superiorities between them, so 4X4 owners looking to swap this into their rig need not be careful of the unit they choose.

We sturggled with the placement for this venerable gearbox, bouncing around between 2nd and 4th, ultimately ending up here. Its super-heavy weight is what tipped the scales (pun intended). But make no mistake, many off-roaders would, and do, happily bolt on the extra 40-or-so pounds that this 3-speed carries on its hips. The 465 is one of the strongest manuals ever to be made, and with it’s short length, it’s a solid setup for 4-wheel drives, long and short.

• What we like: A super-heavy-duty transmission capable of handling insane amounts of torque. Incredibly low first gear. Available PTO (power take off) port. Relatively small package.
• What we don’t like: The heaviest of the manual transmission in our list of favorites. Non-helically cut first and reverse gears made it difficult to shift from 1-to-2, and from R-to-1.
• What it came in / When it was available: The SM465 was available from 1968 to 1991, and could be found in ½, ¾ and 1+ ton GM trucks. The SM465 was purportedly also found in some busses and heavy equipment, but we’ve not been able to confirm this.
• Identification: The SM465 can often be confused with an SM420 to the novice eye. A couple items will make this transmission stick out though. First, there is at least 6 major ribs (3 per side, vertical and horizontal) on the case of this all-cast iron transmission. There are 8 bolts holding the cast iron top cover in place, situated in an odd hexagonal pattern.
• • Make: GM / Muncie
  • Height 18″
  • Case: Cast iron (w/ aluminum top in later models)

#3: The Borg-Warner T18

The T18 is a renowned manual transmission and it is the successor of the also-well-known T98 transmission, with several improvements made on it. The T18 was used in ½, ¾ and 1+ ton trucks, and used by manufacturers such as Ford, Jeep and International Harvester trucks. It’s fully synchro-meshed, helically cut 2nd, 3rd and 4th gears make it relatively easy to shift while driving, but this transmission really comes into it’s own with a super-low range first gear – 6.32:1.

For the non-Jeep fanatics out there, the T18 may be a bit aloof, as it is less common in conversions outside of the Jeep world, than is the SM or NP-series manuals. It was found in a number of Fords and corn binders, but it never got the press that it so deserved. Make no mistake though, this relatively small and lightweight 3-speed packs a knock out 1-2, err… 1-2-3-4 punch. It can take just about as much horsepower as you can throw at it, it has a number of aftermarket upgrades available for it, and it’s steep 6.32:1 granny gear is quite welcome to the stick-shift lovers out there.

• What we like: A very stout transmission capable of handling tremendous amounts of power and torque. Easy to find and cheap to maintain. Super-low first gear. Available PTO (power take off) port. Relatively small package.
• What we don’t like: Heavy for its size. Multiple versions of this transmission make it difficult to identify the submodels (Jeep released 12 versions of this alone). There were also significant differences in strength between the Ford, Jeep / IH version, so be sure to check for the numbers “13-01” on the casting, which indicates a Ford T18. Buyers also need to beware of multiple gear set ranges, which ranges from 6.32:1 – 1.00:1 all the way to 4.03:1 – 1.00:1.
• What it came in / When it was available: The T18 was available from 1966 to 1990, and could be found in ½, ¾ and 1+ ton Fords, Jeep and IH trucks. Some Ford dump trucks used this transmission as well.
• Identification: This all cast iron beast is relatively easy to identify. It’s unusually narrow for a heavy-duty manual transmission, making it a great fit for cramped-quarters 4×4, and features small, but adequate horizontal ribbing. In early models, the T18 may be adorned with a T98 casting stamp, even though it’s a legitimate T18. In this case, you may have to remove the top cover to check the innards. There are two main top-cover designs to the T18. The first is the Ford design (identical to the T98), which is a 6-bolt rectangle with a rectangular protrusion on the rear, driver’s side. The second is the Jeep design, which is also a 6-bolt cover, but is a simple rectangle with no protrusions.
• • Make: GM Borg-Warner
  • Height 17.6″
  • Case: Cast iron

#2: The New Process NP435

The NP435 darn near made it to number one in our list of favorite manual transmissions, and that shouldn’t be a surprise to anyone, since it was a favorite of every Detroit-Iron manufacturer too. It was such a great transmission that Ford, Dodge and GM alike used it in their ½, ¾ and 1+ ton trucks.

The NP435 is also one of the longest-running manual transmissions in this class of all time. New Process started manufacturing this simple, yet strong transmission in 1964 and the last units rolled off the assembly line in 1993. They’re easy to identify, with their cast aluminum top cover and their incredibly simple, smooth cast iron housing.

The NP435 came in 4 major models: NP435A (Dodge and GM), NP435L (Ford Dodge and GM), NP435D (GM), and NP435E (Ford) with 1st gear ratios ranging from 4.56:1, 6.68:1, 4.90:1 and 6.68:1 respectively. In our opinion, the NP435L is the preferred transmission of the group due primarily to its broad gear ratio range and low-range first gear.

• What we like: Easy to find and cheap to maintain. Very low first gear. Available PTO (power take off) port. Relatively small package.
• What we don’t like: non-helically cut first and reverse gears made it difficult to shift from 1-to-2, and from R-to-1.
• What it came in / When it was available: The NP435 was available from 1964 to 1993, and could be found in ½, ¾ and 1+ ton GM, Ford and Dodge trucks.
• Identification: The NP435 is also an easily identifiable transmission. From a distance it can be identified with it cast-iron main body, which has smooth lines and no ribbing. The top cover is cast aluminum with a 8-bolt rectangular pattern. The input shaft on this transmission is graced with an unusually long pilot tip (nearly ¾ of an inch). The Ford and GM versions sport a 6/5″ input shaft with ten splines, while the Dodge versions have a 8 3/8″ input shaft and 23 splines.
• • Make: New Process
  • Height 17.7″
  • Case: Cast iron (w/ aluminum top)

#1: The GM / Muncie SM420

The SM420… the crème de la crème, living proof that the greatest things can come in small packages. The SM420 is, in our opinion, the perfect off-road-worthy manual transmissions of all time. This tranny may be long in the tooth as some units are now pushing 60 years in age, but don’t let a few gray hairs fool you – this transmission will soak up insanes amounts of horsepower without so much as asking for an oil change every few years. It’s lightweight, short and incredibly strong. Oh yeah, did we meantion that the SM420 has the deepest, stump-pulling, granny gear ever available in an OE, retail setting? 7.02:1… now that’s deep.

Made by Muncie for General Motors, the SM420 is a die-hard, work-horse transmission that was available in trucks rated from ½ ton to 2 ton. This stick shifter came with fully synchro-meshed 2nd, 3rd and 4th gears making every-day street driving bearable.

When you couple each of the characteristics of this transmission; a short length, light weight, wicked-low first gear, and superior strength, it truly is the perfect combination for nearly everyone looking to put a manual transmission into their rig. It will fit perfectly in the shortest of rigs, and it can also handle the stresses of a very heavy 4-wheel drive truck that has big-block power within.

Supplies of this transmission are diminishing though, and if you’re considering this manual gearbox for a swap, you’d better start looking fast.

• What we like: A super-heavy-duty transmission capable of handling insane amounts of torque. Wicked low first gear. Available PTO (power take off) port. Relatively small package.
• What we don’t like: non-helically cut first and reverse gears made it difficult to shift from 1-to-2, and from R-to-1.
• What it came in / When it was available: The SM420 was available from 1947 to 1967, but a military version was available up through the early 1980’s. These transmissions could be found in GM trucks, busses, heavy equipment and various military applications.
• Identification: The cast iron top-cover uses 8-bolts to retain it, in a rounded-off “house” shape. There’s also a large bulge on the passenger side to make room for the reverse idler gear. It measures 10.4″ in length and 17″ in height.
• • Make: GM / Muncie
  • Height 17″
  • Case: Cast iron

#5: THM350 (a.k.a. Turbo 350, CBC-350, Thurbo Hydra-Matic 350, TH350)

The THM350 (Turbo 350) transmission has been revered by the automotive community since its inception, and has often been denoted as the worlds finest automatic transmission. While we won’t argue that, we will say that it barely squeaked into our top-5 list of slushbox trannys for a variety of reasons – largely because it is the signature of simplicity, and because it is the essence of function over form.

The successor of the PowerGlide (2-speed transmission), and originally nick-named the 3-speed PowerGlide, the Turbo 350 slush box entered production in 1969 under a joint-production between Chevy and Buick (hence the name CBC350 (Chevy-Buick Combined)). The Turbo 350 was prevalent in nearly every GM rear wheel drive car and light duty truck through 1981, and was mostly paired with V6 and small-block V8 engines. In 1981 a lock-up torque converter version was released, and the transmission was rebadged as a Turbo 350-C (THM350C). This was done so that GM could help fight the gas-crunch, as the electronic lock-up converter would increase fuel efficiency at cruising speeds. The Turbo 350 was installed in its last vehicle in 1984.

While the THM350 is a solid automatic transmission with a huge list of aftermarket accessories available to it, don’t expect to slide it behind your 400+ horsepower engine though as it will fold like a lawn chair with too much power. Supplies of this transmission are excellent, and it can be had for pennies on the dollar in comparison to other automatics, making it quite popular for many off-road enthusiasts.

• What we like: Light enough you can bench-press it into place (almost). Strong enough for moderately built motors (likely capable of handling 375-400 HP with some mods). Lots of aftermarket support. Super reliable.
• What we don’t like: Not able to take the stress of high-horsepower / high-torque motors. Moderately weak bellhousings (although HD “K” cases are available)
• What it came in / When it was available: The THM350 can be found in nearly every light and medium, rear wheel drive (and 4X4) car and truck from 1969 to 1984.
• Identification: The THM350 is a small-package transmission measuring just under 22″ in leght (yup, under 2 feet long). It is a smooth bodied (ribless)all-aluminum cast-housing transmission and can easily be identified by its 13-bolt oil pan that resembles a “square with a corner cut off”.
• • Make: GM / Hydra-Matic
  • Weight: 120 lbs.
  • Gearing: 2.52, 1.52, 1.00

#4: C6 (a.k.a. “Cruiseomatic”)

Ford’s C6 transmission is one of those slush boxes that just didn’t get enough play. This silent hero was based largely on the C4 transmission platform and designed to deal with the growing size and horsepower that Ford was starting to crank out in the mid 60’s. The C6 shared the exact same gear ratios, but was adorned with a series of internal and external upgrades so that it could be made to handle a lot more power and torque. Purportedly, the C6, in stock fashion, could soak up 500 ponies and 500 lb/ft or torque.

Manufactured from 1966 to 1996, this 30-year veteran still sees action today on the dragstrips and in full-size 4-wheel drives such as the Bronco and F-Series. The C6 makes it to our top-5 list of automatic transmissions because it’s a simple, effective transmission that can take a lot of horsepower, and asks for little in return.

Supplies of this transmission are also quite plentiful, and you’ll find them bolted behind full-size Ford cars, vans and trucks alike. It’s longer than most automatic 3-speed transmissions, making it difficult to squeeze into place in short wheel base 4×4’s, but certainly well worth it if you can find the extra 5 or so inches as it will take quite a beating.

• What we like: A very stout 3-speed transmission capable of handling lots of power and torque. Low maintenance requirements. Factory / Aftermarket options for trans-mounted parking brake.
• What we don’t like: Extremely heavy (200+ pounds), too long for short 4×4’s. Only slightly-better-than-average 2.46:1 first gear.
• What it came in / When it was available: The C6 was available from 1966 to 1996, and could be found in the following cars / trucks: Bronco, F-Series, Fairlaine, LTD (I & II), Ranchero, TBird, Torino, Comet, Cougar, Meteor and Montego.
• Identification: While the Ford C6 is the bigger brother of the C4, they share very few identifying characteristics. C6’s can be identified primarily by their smooth cast features, their 33″ length, and their notched, square oil pan.
• • Make: Ford
  • Weight: 203 lbs.
  • Gearing: 2.46, 1.46, 1.00

#3: Torqueflite 727 (a.k.a. A-727, Torque Flite 727)

The TorqueFlite A-727 is a three speed automatic transmission with a long heritage and roots that go all the way back to the ‘Leave it to Beaver’ era. Its predecessor, the 2-speed PowerFlite model, was introduced back in 1954, and the 3-speed TorqueFlite version was hot on its heels, being introduced in the 1956 model year.

Fast forward a decade, to 1962. The A727 model (later named the 36RH, and 37RH) was released to replace an aging A488 model and received several, badly-needed upgrades. With an all-new, all-aluminum case, the tranny shed some 60 pounds on the scale, but was now stuffed with a new parking pawl, and several other internal improvements to help transfer Detroit’s newly found muscle from the engine to the tires.

The A727 was available in two primary options; the standard model, typically found in large rear wheel drive cars, and the heavy-duty model which was typically found in their larger 1/2, 3/4 and 1+ ton trucks (both 2 and 4wheel drive models). The A727 HD was, and still is, sought after by drag racers and monster truck racers because of its vast controllability and tremendous strength – the A727 can quite easily soak up 500+ horsepower and 400 lb./ft. of torque with just a few simple modifications. The TorqueFlite 727 was such a popular slushbox that it was used by other manufacturers around the world, such as Range Rover, AMC, and Monteverdi.

• What we like: Available “HD” models easily take as much power and torque as you can throw at it. Well-built 727’s can take as much as 1,200 HP.
• What we don’t like: Too darned heavy, moderately geared first gear (2.45:1)
• What it came in / When it was available: Available as an HD option in big Chrysler cars and 1980-83 Wagoneers with 6 cylinder engines. Grand Wagoneers from 1984-87 used them too, and was used in Jeeps from ’80 – ’92.
• Identification: The 727 transmission has an odd-shaped transmission pan with 14-bolts, and a 2-piece main body. Look for two, half-round bulbous projections coming out of the driver’s side of the transmission. The 727 used either a 10.75 in or an 11.75 in (273 or 298 mm) torque converter – be sure to grab the 11.75″ version.
• • Make: Chrysler
  • Case: Cast aluminum

#2: THM400 – TH475 Model (a.k.a. 3L80, TH400, Turbo 400, Super Turbine 400)

The THM400 was first introduced during the 1964 model year in Buick’s and Cadillac’s, and the following year it was introduced throughout many of the GM family’s automotive and truck line. During its 27 year “civilian” run (final units rolled off the assembly line in as the 3L80 in 1991), it received several refinements and changes, including the nomenclature change of 3L80. The THM400 was such a revered transmission, that other auto manufacturers such as Ferrari, Jeep, Jaguar, Rolls-Royce, and AM-General utilized it in several of their models. Even today, the U.S. Army HUMVEE still uses the THM400 transmission.

Turbo 400 transmissions are incredibly popular in drag racing, monster truck racing and off-road racing. This is due to their unbelievable strength, primarily due to their use of a cast iron center support which suspends the concentric shafts that join the clutch assemblies. Furthermore, the use of a large, multi-plate clutches allows the TH400 to withstand insane amounts of torque.

There are two such sub-models of the THM400 family that make our top-10 list though; the THM475, and the 3L80HD. The TH475 model was introduced in 1971 as an “extra heavy-duty” model, and could be found in the 3/4 and 1+ ton model trucks, while the 3L80HD was introduced in 1987 in the same class of trucks. 3L80 stands for 3-speeds, L-longitudinally positioned, and 80-8000 lbs. GVW.

• What we like: A bullet-proof transmission able to soak up as much horsepower and torque as you can throw at it. Relatively light weight.
• What we don’t like: Mediocre 1st gear ratio (2.48:1). Usually too long for short-wheel base 4×4’s. No overdrive.
• What it came in / When it was available: The TH400 (475 model) was available in 1971 and up 3/4 to 1+ ton trucks. The 3L80-HD could be found in 1987 and up 3/4 to 1+ ton trucks.
• Identification: The TH400 has a 1-piece cast-aluminum housing that is quite smooth (ribbings only found near the tail cone). It’s most easily identifiable by looking at the oil pan, since it’s shaped like the state of Texas.
• • Make: GM / Hydra-Matic
  • Weight: 135 lbs.
  • Gearing: 2.48, 1.48, 1.00

#1: TH700R4 (a.k.a. 4L60 / 4L60E)

The TurboHydramatic 700R4 transmission is, in our opinion, the finest automatic transmission ever made, yet has one of the most checkered pasts. In the very early 80’s, car manufacturers were under serious pressure to deal with increased fuel economy demands, which brought about the introduction of “overdrive” transmissions. GM responded to the call with the 700R4 series, which was also a replacement for the aging TH350 transmission.

Although plagued with a variety of bugs in its first years of production, GM sucked it up and continued to make improvements on this foundation, and by 1987, the TH700R4 was in its prime – and is now considered by most experts (and us) to be the most refined, and reliable automatic transmissions ever made. Even the early model TH700R4 transmissions can be “upgraded” with better servos, gears, clutches and slingers to make them as good (or better) than the later-model units.

This transmission is also blessed with three very important aspects. First, it has a very low range first gear (3.06:1), making it sought after by hot rodders and off-roader’s alike. Second, it came with a 30% overdrive (0.70:1), making it appealing to everyone because of the on-road fuel savings. Thirdly, this transmission came stock with either a vacuum controlled or ECU controlled lock-up torque converter.

It’s also strong enough to handle big block power and massive amounts of torque. Later in its life, it was re-badged as the 4L60 and carried this name until 1993, when the 4L60-“E” model (electronic shift control) was introduced. 4L60 is an acronym that stands for 4-speeds, L-longitudinally positioned, and 60-6000 lbs. GVW – a naming convention still in use by GM today (there’s something you can impress your friends with).

• What we like: Unusually low first gear (3.06:1) for an automatic. Easy to find. Overdrive. Later models are bulletproof, especially the “K” case versions.
• What we don’t like: Early model bugs, some overheating issues with mal-configured lock-up converter switches.
• What it came in / When it was available: The TH700R4 (a.k.a. 700R4, 4L60, and 4L60-E) was available from 1982 to current General Motors cars and trucks.
• Identification: The 700R4 is relatively easily identifiable by two main characteristics. First, it is an all-one-piece cast aluminum housing (bell housing and main body are all one piece). Secondly, it has a square oil pan, differing from the cut-off-corner TH350 or the Texas-shaped TH400. Pre-1984 versions had a 27 spline input shaft, which was changed to a 30-spline later. For purchasers wanting models that pre-dated the “late model 4L60-E” versions, they should look for a square, 4-bolt tail housing, versus the 6-bolt version.
• • Make: GM
  • Weight: 155 lbs.
  • Gearing: 3.06, 1.62, 1.00, 0.70