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No Power?

Discussion in '1982-Present GM Diesel' started by dallassnowman, Feb 26, 2005.

  1. dallassnowman

    dallassnowman 1/2 ton status

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    I was pulling a pop up camper(bare no ac, not loaded) and going up hill. My K5 kept going slower and slower. What can I do OR whats wrong. Is it my tires?
    16 rims and 33's
     
  2. joez

    joez 1/2 ton status

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    What gearing do you have? Tranny?

    Was the truck smoking as it was slowing?
     
  3. dallassnowman

    dallassnowman 1/2 ton status

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    All stock

    and I don't think it was smoking.
     
  4. joez

    joez 1/2 ton status

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    Stock is a relative term. Some trucks got 3.08's, some got 3.73's, some got even lower. Depending on the gearing you have, it COULD be the tires. I run 3.73's and 36's, though, and while it is a dog, it works. Its much happier on the 33's.

    Did it used to pull this hill and now its just a dog, or was this the first time you towed with it? Mine will slow down on steeper hills unloaded depending on wind, how fast im going, and if i want it to downshift or not.
     
  5. dallassnowman

    dallassnowman 1/2 ton status

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    This was the first time I towed with it, but it usually does slow down some without towingHow do I find out what gearing I have???
     
  6. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    How much would you say the trailer weighs?


    Rene
     
  7. dallassnowman

    dallassnowman 1/2 ton status

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    No more than 2000lbs.
     
  8. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    That shouldn't have made much if any difference at all, unless you have really poor gearing.

    Check your glove box and look at the option codes. Look for "G" codes. G80 is a Gov-Lock, and then you'll see GT4 or GT5 etc etc. Post up what you find, and we should be able to tell you what gearing the truck has.

    Being early 80's I wouldn't be surprised if it had 3.08's and an overdrive...

    Rene
     
  9. dallassnowman

    dallassnowman 1/2 ton status

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    option no-1GQ1--REAR AXLE STANDARD
     
  10. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Keep looking and see what else is there...



    GT1 - AXLE REAR 2.56 RATIO, 10,500 KG
    GT2 - AXLE REAR 4.77 RATIO
    GT3 - AXLE REAR 4.55 RATIO
    GT4 - AXLE REAR 3.73 RATIO
    GT5 - AXLE REAR 4.10 RATIO
    GT6 - RATIO TRANSAXLE FINAL DRIVE 4.19 (USE OPTION FV5)
    GT7 - AXLE REAR 3.33 RATIO
    GT8 - AXLE REAR 4.10 RATIO
    GT9 - AXLE REAR 2.87 RATIO
    GTY - AXLE WIDE TRACK
    GU1 - AXLE REAR 2.41 RATIO
    GU2 - AXLE REAR 2.73 RATIO
    GU4 - AXLE REAR 3.08 RATIO
    GU5 - AXLE REAR 3.23 RATIO
    GU6 - AXLE REAR 3.42 RATIO
    GU7 - AXLE REAR 2.77 RATIO
    GU8 - AXLE REAR 3.90 RATIO
    GU9 - AXLE FRONT 3.91 RATIO
    GV0 - AXLE FRONT 3.55 RATIO
    GV1 - AXLE REAR 2.73 RATIO
    GV2 - AXLE REAR 5.83 RATIO
    GV3 - AXLE REAR 3.08 RATIO
    GV3 - RATIO TRANSAXLE FINAL DRIVE 3.57 (USE OPTION FQ4)
    GV4 - AXLE REAR 5.428 RATIO
    GV4 - AXLE REAR 3.36 RATIO
    GV5 - AXLE FRONT 3.82 RATIO
    GV5 - AXLE REAR 3.55 RATIO
    GV7 - AXLE FRONT 4.05 RATIO
    GV7 - AXLE REAR 4.11 RATIO
    GV8 - AXLE REAR 2.72 RATIO
    GV9 - AXLE REAR 4.25 RATIO
    GVW - FAMILY CODE GVW RATING
    GW1 - AXLE REAR 3.91 RATIO
    GW2 - AXLE REAR 2.56 RATIO
    GW3 - AXLE REAR 2.56 RATIO
    GW4 - AXLE REAR 3.31 RATIO
    GW5 - AXLE REAR 2.73 RATIO
    GW6 - AXLE REAR 3.27 RATIO
    GW8 - AXLE REAR 4.10 RATIO
    GW9 - AXLE REAR 2.93 RATIO (DUP WITH GU3)
    GWL - SPRING REAR 9,000 LBS
    GWP - PLANT CODE GLIWICE, POLAND
    GX1 - AXLE REAR 5.429 RATIO
    GX1 - AXLE REAR 3.70 RATIO
    GX2 - AXLE REAR 3.07 RATIO

    Standard ratio is 'likely' 3.08

    Rene
     
  11. dallassnowman

    dallassnowman 1/2 ton status

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    This was in glove box and another sticker that just says not to put a slide in camper on truck....

    [​IMG]
     
  12. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Welp, that sucks. The only way to be sure now is to pull the cover off the rear, spray some brake kleen in there and rear the numbers off the edge of the ring gear.

    I'm betting 3.08's though, and with 33's and pulling 2000 lbs it could very well turn into a huge dog on any grade.

    Does it still drive the same as always without that little trailer?

    Rene
     
  13. dallassnowman

    dallassnowman 1/2 ton status

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    Yip...

    this kinda worries me cause the wife wants a travel trailer, like a 15ft!
     
  14. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I'd seriously look into 4.10's for your truck. You could tow in drive and the rpm's would be ~2500 or so on the freeway, yet when not towing they'd be ~1900 or so (in OD) so mileage shouldn't suffer much if any.

    A 15 foot trailer usually doesn't wiegh much more than 3000 lbs and shouldn't be any trouble to tow...even with a NA 6.2. A while back Arveetek posted a pic of his NA 6.2 pick-up towing a 29 foot 5th wheel. It was slow, but it did do the job and I am pretty sure he runs 4.10's and even smaller tires than you do.

    Gearing is crucial, it mulitpies the engine torque and determines what rpm the motor spins at at a certain speed. If the motor is loping at well below it's torque peak it will rapidly fall on it's face on grades. If your truck does have 3.08's it is only spinning 1800 rpm at 60 mph in Drive and 1260 rpm in OD. If you're making 200 lbs of torque at 1800 rpm, the torque at the ground in drive would be 616 lbs.

    With 4.10's at the same rpm in drive you'd see 820 lbs at the wheels, and at 60 mph (2500 rpm and likely 250 lbs of torque) you effectively see 1025 lbs or nearly double the power at the same speed. Also, with 4.10's you have a 500-700 rpm cushion when you do get to a grade before you drop out of the torque peak (assuming 60 mph at the beginning of the grade)

    It'll never tow like a Cummins or any other new diesel, but there is no reason it can't tow a modest camper trailer easily IMO.

    Rene
     
  15. dallassnowman

    dallassnowman 1/2 ton status

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    WOW you seriously answered alot of my questions and started a new problem....now I need to look at replacing more stuff!!!!!I thought if it were a standard it would help by down shifting..so this all makes sense now.
    So where do i start cause this truck isn't going anywhere. Only deeper in my pocket!!:cool1: :k5: :1zhelp: :1zhelp::1zhelp:
     
  16. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    First thing I'd do is confirm your current gearing though. Pull the diff cover and find the numbers.

    Lets start with the tranny issue regarding what is better. IMO the SM465 can be a pain to tow with. On grades if you have to shift out of 4th you're going to lose almost half your speed to keep the rpms down to a sane level. The 700R-4 you have will unlock the convertor first (as you appply more throttle) then it will shift down one gear. A comfortable speed in second gear with a 700R-4 is going to be higher than 3rd with an SM 465.

    The biggest con with the SM 465 is again on a grade and towing, it's easy to get the speed and rpm's up in 3rd, but in the time it takes to stuff it into 4th, plus the huge gap in ratios it'll fall on it's face almost immediately. This has been my experience, but keep in mind that was towing a 5500lb trailer through the mountains here and some very long steep grades.

    For what you intend to tow I would stick with the 700R-4, and just keep it in Drive when you're towing. A big stacked plate cooler and a tranny temp guage are both good investmants.

    As far as gearing goes I would say 4.10's would be good for the tire size you're running. Two ways to go about that are to regear the 10 bolts which would probably run $400 per diff installed (you might find that higher or lower...that's a ballpark) The other way is to swap a set of 3/4 ton diff's under the truck. 3/4 ton diff's most often come with 4.10's already, and you can likely pick up a front and rear matched set for $400 or less. If your current tires are near new I'd pick up a set of 15x8 8 lug rims and have them mounted up. If you're due for tires I'd probably run 16" rims and whatever tires. 15" 8 lug rims will let you use your current tires with the 3/4 ton diff's, but you will need to grind the front brake calipers to clear them properly.

    Either way will probably run you near enough to the same amount of money, but by going 3/4 ton you would be gaining strength and reliability, but more importantly to me you gain larger brakes.

    When my truck was also a tow rig for our 21 foot trailer my Jimmy had 10 bolt/12 bolt with 2.73's, SM 465 and 33x12.5 BFG Mud's on it. This was with my 350, and until I hit the hills it was 'OK'. I would have to run 70 mph on the flat sections to keep the rpm's up high enough that it wouldn't fall on it's face. Hills were a joke and on many I was down into 2nd gear because the tall gearing was killing me.

    I swapped in a set of 3/4 ton diff's with 3.73's and it instantly became a ton better to tow with. Flat ground I could stay around 60 if I wanted, because my cruise rpm's were now higher and the motor was near it's torque peak. hills would drop me down to 3rd gear if it was steep enough, but at least I could maintain my speed in that gear and keep speed around 35 mph. With the 2.73's I'd be down to under 20 mph on the same hill and same trailer.



    Rene
     
  17. chevy_addict

    chevy_addict 1/2 ton status

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    Rene,

    This is EXCELLENT information. I have been contemplating replacing the 700R4 in my Suburban with a SM465 simply because of strength. It never occurred to me that the gear splits on the SM465 would not be ideal for towing a 5-6K travel trailer (especially on hills) and that I might be better off by keeping the 700R4.

    Thanks
    Dave
     

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