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post #1 of (permalink) Old 11-11-2002, 08:56 PM Thread Starter
 
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77 1/2 ton specs?

My bro's 78 mud truck blew the stock Th350. I have a Jasper TH350 laying in a barn for my mudder, but we found a 77 1/2 ton, 350, 4spd manual (L, 1,2,3,R), 4x4 (NOT P 203)... I would consider having my brother buy this 77 and I would give him my Jasper case for the 4 speed, but I know nothing of this model tranny. Is it strong, weak, dime a dozen, too rare for parts? Please give me some input before we buy the truck and find out ourselves...
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post #2 of (permalink) Old 11-11-2002, 09:47 PM
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Re: 77 1/2 ton specs?

I'm pretty sure it's a SM465. I think they quit making the SM420 in 71 or something (memory is a little fuzzy tonight). Anyway, you can find pictures of such things all over the internet, including here at ORC.

SM420s and SM465s are pretty bulletproof. People like both. They're both pretty common but the SM420 is getting old. Usually find them hooked to NP205s except in the late eighties you'd find them hooked to NP208s.

You can usually find 465s in the $150 range. 420s are getting rare so they're getting expensive but also people don't know what they are so sometimes you can get them cheap.

I, myself, have never really liked either. They suck for city driving in my opinion. They're great offroad transmissions though. All the ones I've used are sloppy and they didn't like to shift under power like a T5 or T56 will. If I had an offroad-only machine I'd definitely be looking for a 465.
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post #3 of (permalink) Old 11-12-2002, 04:33 AM Thread Starter
 
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Re: 77 1/2 ton specs?

The guy told me he has heard the transmissions were junk, thats why they bought another plow truck. So, I might be able to get a good deal, since he thinks only the engine is worth the truck. It does run good, but the body is so far shot its not funny, I'll probably run a $200 offer by him later this week if its there.
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post #4 of (permalink) Old 11-12-2002, 07:22 AM
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Re: 77 1/2 ton specs?

Well, GM put the SM465 in everything from 1/2 2wd to 2 1/2 if that tells you anything about their strength. They are probably a little tough in the city, but are as bullet proof as a stock tranny gets. Put a NP205 behind it, and you'll have a setup that's hard to kill, especially for the price.
post #5 of (permalink) Old 11-12-2002, 08:27 AM
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Re: 77 1/2 ton specs?

I'd bet money that's a SM465. There was a different manual tranny GM put in the fullsizes back then, but it was exceedingly rare, and I'm pretty sure only put in the 2wd half tons. Forget which one though, would have to go consult the stack of 4x4Power's.[img]images/graemlins/tongue.gif[/img]

If the transfer case isn't a NP203 like you think, then it's a NP205. Have you driven it? Make sure they work before you spend any money on it. He might just mean the tranny (or transfer case) is goofed up.

If it is a 465 and 205 and it all works, GO FOR IT!
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post #6 of (permalink) Old 11-12-2002, 03:49 PM
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Re: 77 1/2 ton specs?

hell yea, sm465. i have one, it is rough in the city, i use granny in traffic [img]images/graemlins/wink.gif[/img] but knowing how durable it is, it dosnt get to me, but i have the sm465\np208 combo, but my truck is an 87 and that was stock, so i cant complain. [img]images/graemlins/grin.gif[/img]
post #7 of (permalink) Old 11-14-2002, 04:31 AM Thread Starter
 
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Re: 77 1/2 ton specs?

So, the L on the shifter is actually a granny gear? Does anyone know how low the ratio is in first, compared to 1st in a 3spd th350? What I am saying is, will it give me more torque to make up going from 4.11s to 3.73s? (the 4.11 setup was all cobbled up and a front axle was snapped, I took the cheapest way out...)
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post #8 of (permalink) Old 11-14-2002, 03:10 PM
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Re: 77 1/2 ton specs?

lol, that L gear is granny, it is 6.55:1, which kicks ass if your a torque junky, but winds up really quick, very handy for long down hill decents off-road, or traffic in teh city [img]images/graemlins/wink.gif[/img]. 1st gear is somthin like 4.50:1, the first gear in a th350 is somthin like 3.50:1 for a first gear. anyway, as everyone says, that sm465, more then likely the tranny in that 77' is a very stout trans. good luck on that.

[img]images/graemlins/grin.gif[/img]
post #9 of (permalink) Old 11-15-2002, 08:09 AM
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Re: 77 1/2 ton specs?

I had a 456 in a k5 with a weak 305 and 3.42ish gears and 31's. I rarley used the granny, its non syncronized and tops out quick. 1rst gear(actually 2 gear but what ever) is what you start out in and use in normal driving. Granny is very low. I could damn near dump my clutch from idle and not kill my engine in low. Its tough as hell as trannys go.

It dosnt shift like a 6 speed vette. Its a truck though so I dont anticipate you are planning on dragracing it, right? I always got the feeling I was rowing a boat when I shifted[img]images/graemlins/crazy.gif[/img]....that sucker had quite a bit of shifter travel if you know what I mean [img]images/graemlins/wink.gif[/img] Its a truck though so what else do you expect? [img]images/graemlins/tongue.gif[/img] [img]images/graemlins/laugh.gif[/img]

The only thing I didnt like about it is the spread between gears is pretty big......but since you aint dragracing you will be more than fine with it on or off road.

Did I mention granny is low especially when combined with low range? [img]images/graemlins/smirk.gif[/img]

post #10 of (permalink) Old 11-15-2002, 04:13 PM
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Re: 77 1/2 ton specs?

yea, when i got my truck i had to drive around and get used to it, i ground granny a few times, and ever so often i do because i miss 2nd and skid into granny, but its a dead wall of grinding, once in a while when im going very slow i can get it in very easily, but now its just like driv'n a 3 speed, i use granny when slow speed and lotta torque is needed. yea slam it in granny and throw it in 4lo you will creap, very useful for long downhill decents off-road and the such, but truely once you go sm465, you never go back [img]images/graemlins/wink.gif[/img] .
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