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Auto, or standard for offroading?

Discussion in '1982-Present GM Diesel' started by Russell, Jan 27, 2007.

  1. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Hey guys!

    I'm building up a K5, and will soon have a mechanically injected `93 6.5TD available coming from a truck I am buying for the NV4500 I'm stabbing into my 3/4 ton.

    While the 6.5 does need some work (could be simple, could be spicy, don't really know till I get the 1 ton), I'm thinkin I'll put it into the K5. The K5 was originally a 6.2 diesel truck, and already has all the wiring under the dash intact, the diesel rad / core support, hydroboost etc. I'd just need to build / buy an engine harness, then wash out the fuel lines to get it running :)

    Anyways, I'm planning on running a 4" lift with 52" springs up front, 63" out back, and 33" tires, with 4.10 3/4 ton diffs, detroit locker in the 14 bolt, but I'm still debating on what to do with the transmission. The two options in my mind is either a TH350 / 700r4, since neither needs a vaccum signal, or an NV3500 / SM465.

    Which would you guys go with? The truck is not a mud bogger (though it is sometimes unavoidable, if you know what I mean ;) ), but is going to be a trail runner, that goes slow over some pretty steep terrain.

    I just see the diesel as the best option as it'll run at any angle, will idle up most anything, doesn't have any electronic ignition components to fail if they get wet, better for the environment, and better on fuel too. Not to mention having that cool factor, esspecially with a straight pipe off the turbo :wink1:

    What do you guys think?
     
  2. CDA 455

    CDA 455 3/4 ton status

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    Man, such a loaded question!

    After 30 years with a manual, I'm going to put an automatic in my K5 just because I like the idea of 'shift into drive' and go.

    Bottom line is, it's purely preference. Both are perfect for the job.
    I'm changing because I'm becoming lazy, nothing more.








    Although I am eye-balling the NV5600 :D !!
     
  3. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I really like the manual for getting more power to the ground in general, and providing a ton more control off road. We have pretty mountainous terrain, so for me having epic engine braking is a big plus. As for obstacles, when it gets technical I can, and often do, wheel with my feet flat on the floor and let the truck idle up and over stuff. The diesel is very strong at idle...

    Rene
     
  4. imiceman44

    imiceman44 1 ton status

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    I used to sit on my window sill and watch and steer because my hood is so high I can't see the rocks. You can't do that with a gas engine. :haha:
    I would go manual if you are going to go really slow, the auto will get you there but if you are so slow that you are using the multiplication of the torque convertor, you will over heat the tranny, with the lower gears in the manual you could be crawling wih no heat.
     
  5. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Ok, you guys have convinced me, standard it is! I love standards anyways, so thats fine, lol

    Next question is if I should go for the SM465 / 205 combo I've got, or if I should go with an NV3500 / NP241 combo, which I don't have either of...

    SM465 certainly has a better low gear, but the NP241 has a great low range too. NV3500 isn't quite as tough, but has closer spaced gears, and 5 of them to keep the diesel in it's powerband. I can't think of any reason why the thing wouldn't hold up if I'm not trying to powershift it or something...
     
  6. Leper

    Leper 1/2 ton status

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    The 241 may be a weak link in that setup.
    I like an auto. A 400 would last behind the diesel. Yes, you lose some power through a slushbox. For me though, its just easier to use the auto. Less to think about.
     
  7. diesel4me

    diesel4me 1 ton status Premium Member

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    your choice...

    A TH400 or a TH350 will need a vacuum source to run the modulator valve..

    I prefer automatics,much easier to drive--since I plow with my truck,I find the automatic much easier to plow with, and is easier on the rest of the drivetrain--and no replacing the clutch every year or two....also we have lots of heavy traffic,and I find driving a manual tiring in those conditions..

    But I dont hate standard trannys--at least you can push start your truck if you have a manual,and unless the clutch is completely wasted,chances are excellent it'll move when you put it in gear and let off the clutch..an automatic can act up in many ways,from "no drive","no reverse"or "wont upshift",etc..

    I love my automatic,but that love quickly turns to hate if and when it decides to no longer work!..I don't like the fact losing a little fluid from cooler hoses or a hole in the pan can stop you dead in your tracks very much..also I've seen many go out without much warning...you can limp home with a wounded manual tranny most of the time,but you need a tow once your automatic is toast..:doah:
     
  8. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Isn't the 241 rated for more torque than a 205? The weak point would be if a guy nailed it on a rock and cracked it open, lol

    I've already decided I'll put the 6.5L in, since I'll be buying it anyways, but still need to totally settle on which transmission to put in...

    The K5 currently has a 700r4 / 208 combo, with a busted sunshell in the tranny leaving me with only 1st and 3rd, no 2nd, O/D, or reverse :P
     
  9. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    The 241 should be fine, it's the NV3500 I'd be a little concerned about. Input torque might be pushing the design limits of the NV3500, but should still be well within design limits of a 241.

    The thing I don't like about an auto is you have to give it throttle to get it to move, and it can be hard to apply smooth transition between the wheels not turning and getting them turning. This is hard to do without spinning the tires in loose terrain and I find that to be a disadvantage. I've run across a couple of loose off camber climbs that my truck has climbed easily...only to watch my buddy's 700/241 equipped truck have a ton of trouble with. Everytime he'd try and get the truck going a bit he'd give it a little more gas, then a little more and just as the convertor finally stalled the tires would spin because he then had too much throttle. Tires spun, truck slides downhill and his line is gone...lather, rinse, repeat.

    I don't find the manual requires any thought off road...at least no more thought than breathing in after breathing out. i don't buy the three legged argument either as I pretty much never use the clutch when wheeling. In low range if it does stall (it's never happened yet with the 6.2) it'll restart in gear. In low range i also don't need to give it gas while releasing the clutch...it'll climb the tires pretty much vertically at idle.

    A th400 would be OK...if you were running a doubler. Other than that I see it as a big disadvantage. The 700R-4 is a bit better, but only because usually it has the help of a 241's lower low range behind it. Still gonna be dealing with getting the convertor spooled up enough to move the truck.

    I'd go 465/205. It's a proven, tough combo and behind the diesel it shines. I ran that combo behind my 6.2 for three years, and wheeled at BB '03 with that combo. All the technical, tight, harder sections the truck did at idle...

    Rene
     
  10. MattK

    MattK 1/2 ton status

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    in the one time ive wheeled with my stick since i swapped it in i know exactly what you're talkin about. for cruisin around the trail i stayed in high, left the trans in granny and just let the truck to the work. still had plenty of torque to apply the brakes to slow down on flat ground without worryin about stallin/buckin. if you learn where your clutch engages, there really aren't many ways a stick will hold you back on teh trails IMO

    one disadvantage though is hittin mud pits. i cant speak for everyone, but i know i cant shift a 465 as fast as an auto will.
     
  11. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    For mud I used to just leave it in second gear/low range. The K5 is too fat to float on top and that gear/range seems to provide a nice balance of wheel speed and torque.

    Sand dunes...auto rulz.

    Rene
     
  12. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Well, I do have the SM465 / 205 combo kickin around. I need to tear it down though, I get a bit of a scary noise out of it if I rev the engine while the tranny is in neutral, and the clutch is engaged. Sounds a bit like a connecting rod hammering away, but the sound goes away when you push the clutch down.

    That, and the 205 leaks, but, thats easy to fix :D
     
  13. imiceman44

    imiceman44 1 ton status

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    You are saying 33" tires so I am assuming you are doing ligh wheeling, as long as you protect your 241, it's the better choice with the 5 speed, like you said the spacing of the gears will be good for the diesel.
    :D
     
  14. imiceman44

    imiceman44 1 ton status

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    You have a bad throw out bearing or a bad fork.
    If the noise was when you push the clutch in then i would say it's the pressure plate.
     
  15. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Thats possible, but I totally rebuilt the transmission before I put it in, all new bearings, bushings etc, so I'd be kinda surprised if that was the problem. The truck did it really bad when I first fired it up, scared me silly cause I thought I had a rod knock... Its gotten better since then, but still makes that noise at like 2500 rpm and above.
     
  16. imiceman44

    imiceman44 1 ton status

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    Did you put a new throw out bearing and new fork?
    The fork has tabs that sometimes wearout if the bearing goes out and it will be a little off and will rub and shake when not depressed in.
     
  17. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Yep, the throw out bearing is new, but I didn't replace the clutch fork... I guess it is possible that it might be toast!
     
  18. imiceman44

    imiceman44 1 ton status

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    A few issues I have had with clutches:
    -Fork dimples worn out sometimes unevenly too wich makes it worse.
    -Loose pivot ball for the fork, it's rare but it happened to me, started shaking the fork all the time.
    -lost return spring on fork, let's it ride on the bearing and shake since it's loose.
    -adjustment of fork too tight, you need to have a slight gap, the fork shouldn't be riding on the bearing at all times.
     
  19. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Oh, I guess I should mention its a hydraulic clutch setup, though I think I'll try your idea of a return spring, and make sure that the pushrod isn't too tight.
     
  20. cegusman

    cegusman 3/4 ton status

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    I run a sm465/205 behind my 6.2 and love it. The only problem I have right now is running the 52" springs up front. My 1ton cv front shaft is so short that the cv binds up when flexed. I replace mine with a H.A.D. 42 degree cv shaft. Got rid of the binding but now my problem is I have so much flex up front, the shaft pulls apart at the splines. The only solution I can see is to run a doubler to get the front shaft longer with a longer slip shaft. I plan on running a limiting strap on the passenger side until I can afford the doubler though.
     

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