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Thread: Manual Transmission Differances

  1. #11
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    The Novak Guide to the
    GM Muncie SM465 Transmission


    The SM465 is an outstanding, heavy-duty truck transmission designed and used in , 3/4 and 1+ ton trucks. The SM465 was made by General Motors from 1968 to 1991. They are found primarily in GM and Chevrolet trucks, Blazers, Suburbans and many other models falling under the 1/4-ton to 1-1/2-ton platforms.
    The 465 is an intellegently designed and very well-built transmission and remains easy to locate and generally inexpensive to buy and maintain. The strength, relatively short size and the gearing of the transmission make it a good choice for a variety of on-road and off-road situations. It has a very good set of road manners contrasted by its enormous off-road brawn.
    The "SM" in the transmission's designation stands for Syncrho-Mesh, in the tradition of other GM gearboxes. It is also referred to as the CH-465 or CH465 by factory literature.



    Identification
    The SM465 is a top loaded, top shifting truck style transmission. This transmission is 12 " long and features a cast iron top cover that is retained by eight bolts. The SM465 case is of *cast iron. The case itself is generously ribbed both vertically and horizontally.
    The SM465 has a 1-1/8" diameter, ten spline input shaft that has a stick-out of 6-1/2" from the front face of the transmission. The pilot tip is ~19/32" in diameter. The front bearing retainer flange measures an unusually large 5-1/8" in diameter and the bearing retainer tube is 1-3/8" in diameter. The front bolt pattern is the consistent GM Muncie / Saginaw four-bolt pattern as found on GM bellhousings and transmissions from the 1940's through the 1990's.


    Features
    The 465 enjoys a very low compound gear at 6.55:1 and as such it is a popular choice for those wanting a very low crawling gear.
    The SM465 features power-take-off (PTO) ports on the passenger and driver sides of the case.
    The shifting pattern for the 465 is in the standard "H" pattern with reverse gear being to the right side, and down.



    SM465 Versions
    There are three principal versions of the SM465, each based on the era and configuration of the transmission. There is no known mechanical superiorities to either earlier or later versions.
    Earlier SM465
    The earlier era of the SM465 include the 1968 - 1978 transmissions. There were both 2wd and 4wd versions. Internally, they are identical to each with the exception of the transmission mainshaft. The 4wd version of this mainshaft (or "output shaft") has a 10-spline output with a 2-5/8" stickout and an accompanying 4wd adapter housing. The 2wd version has a 35-spline threaded mainshaft compatible with a driveshaft yoke, and accompanying 2wd style tailhousing.



    Later SM465
    The later era of the SM465 include the 1979 - 1991 transmissions. A minor internal change of the 1st gear bushing and thrust washer occurred, in addition to a change from a shorter 10-spline, 4wd output shaft to a 32-spline 4wd output shaft - coinciding with the change of bolt pattern in the New Process 205 transfer case from a figure "8" input bolt pattern to a round, six-bolt input pattern. This pattern was also found on the 208 and 241 chain-driven transfer cases.
    Later 2wd style SM465's also incorporated the same 1st gear bushing and thrust washer change, but the 35-spline, yoked output remained identical.
    1988-1991 Versions
    The last years of SM465 featured a direct-drive (4th gear) switch to signal a lean or cruise mode operation to the GM Engine Control Module (ECM). These final versions had an aluminum top cover and a revised input shaft and input bearing combination. They were found in the C/K Series trucks. Suburbans, however, continued to use the earlier SM465 with the cast iron top cover.

  2. #12
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    What engines will the SM465 bolt up to besides 350?

  3. #13
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    It'll actully bolt to any engine you want it to. The trick is having the right bell housing. With a Chevy Bell housing, you can bolt it to any Chevy House shapped bell pattern. IF you had a BPO (Buick, Pontiac, Oldsmobile, Cadillac) bell housing, then you could bolt to any B, P, O or C engine. Its a very universal transmission. I have heard of it also being using Jeep CJ's and Fords too provided you have the correct bell housing. On my 64 GMC, and the manual Z bar clutch system and bell housing that was in that truck, I ran SM465, M21 and M22 transmissions. I did eventually do away with the SM465 transmisison because it was shorter and I had to use a differant transmission for racing. SM465 is not a good drag race transmission because it can not be speed shifted and you lose alot of time in between shifts. As far as M21 and M22 and Turbo 350 auto, those all 3 used the same driveshaft and yolk. So I could be a 4 speed to an auto in a matter of about 2 hours, just by changing transmissions, which entailed, the shifter, flywheel and clutch and bellhousing. I have a B&M QuickSilver ratchet shifter when I ran the automatic, and I had a Hurst Competition Plus shifter for the Muncies. Also note, the M21 and M22 used differant clutch plates. Differance being the M22 RockCrusher used a fine spline input shaft and the M21 used a course splined input shaft. Same output shaft though, and the same as Turbo 350 auto also. I ran either 1 of the 4 in that truck with no problems, all bolted parts, not cutting, welding or drilling holes. Everything lined up in factory holes in the truck. The same crossmember also worked for the M21, M22 and Turbo 350. So the SM465 was a bit of an oddball.
    85 Sierra Classic K1500
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  4. #14
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    For an example what bellhousing do I need for a 454? What bellhousing do have now on the 350?

  5. #15
    Senior Member Kennyray's Avatar
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    The bell housing you have now is the same for a 454
    None of the secrets of success will work unless you do.

  6. #16
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    Is there a website on cross referencing bellhousing on chevy engines?

  7. #17
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    You don't need to cross referance, that is what I am saying and now Kennyray, the same bellhousing will fit ALL and ANY Chevy patterns like the one you have now shaped like a house. You can do an inline 6, a V6, a small block chevy, a big block Chevy whatever you want. Thats the beauty of Chevrolet and interchangeability.
    85 Sierra Classic K1500
    85 Silverado K10
    84 Silverado C20

  8. #18
    Senior Member Kennyray's Avatar
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    GM in general, put an old 3.8 in a firebird that had a poncho V-8 in it, used the same tranny.
    None of the secrets of success will work unless you do.

  9. #19
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    GM Bellhousing Bolt Patterns

    GM Bellhousing Bolt Patterns
    The General Motors corporation was responsible for producing seven common bellhousing patterns. Allot of engine types shared bolt patterns but several were also exclusive to their own engine family. Below you will find information on which engine uses which bellhousing bolt pattern. You may ask yourself "why do I care about this information?" Well as any true hot roder will know, engine swaps are one of the best ways to make your vehicle the best one of the bunch. But in these cases you may not be so inclined to swap out a perfectly good transmission and drivetrain. So with the information below you can choose any engine that will bolt to your transmission or even figure out which vehicle and engine combination to look for when shopping for a transmission in a junkyard.
    Bellhousing Engines Chevrolet bolt pattern. Used on all Chevrolet V8's to this date. Also used on Chevrolet 90degree V6'sSmall Block Chevy, Big Block Chevy, 3.8L (229ci) V6 (not to be confused with Buick 3.8L), 4.3L V6
    Buick, Olds, Pontiac, Cadillac (BOP) bolt pattern Used on all Buick, Olds, Pontiac and Cadillac's until the cars switched to Chevrolet engines.Buick, Olds, Pontiac and Cadillac V8's, 4.1L (255ci) V6, 3.8L(231ci) V6,
    GM Small Corporate Pattern Used on Chevy 60 degree V6's, 4 cylinders and other FWD engines2.0L (OHV I4), 2.2L (OHV I4), 2.5L (OHV "Iron Duke" I4), 2.8L (60* V6), 3.0L (90* V6), 3.1L & 3100 (60* V6), 3.3L & 3300 (90* V6), 3.4 & 3400 (60* V6), 3500 (60* V6), 3.6L (60* V6), 3800 (90*V6), 3.9L (60* V6), 4.1L V8, 4.5L V8, 4.9L V8
    GM Ecotec 4 Cylinder A late 90's GM 4 Cylinder used across several FWD car lines. An all aluminum engine featuring impressive technology and modern design. 2.0L, 2.2L, 2.4L
    GM 4 Cylinder Pattern Unique to a select line of GM 4 cylinder front wheel drive engines.2.3L (SOHC I4), 2.3L ("Quad Four" DOHC I4), 2.4L ("Twin Cam" DOHC I4)
    Cadillac Northstar Pattern A breed of Cadillac V8's that feature dual overhead cams. Some versions feature variable valve timing as well. 4.0L (Oldsmobile engine built by Cadillac and based on Northstar), 4.6L V8
    Isuzu 4 Cylinder Used in cars and trucks such as the Chevrolet Nova and the Chevrolet S-10. This 4 cylinder from Japan found its way into a few GM vehicles. 1.6L, 1.8L, 1.9L, 2.0L

  10. #20
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    So if the bellhousing and engine bolt pattern matches then it fits right?

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