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Found a rear end but seller is unsure of gear ratio. HELP!

Discussion in 'The Garage' started by BIG B., Jul 28, 2003.

  1. BIG B.

    BIG B. Registered Member

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    Here is what I know. 1984 3/4 ton GMC Suburban w/14 bolt rear. Engine is 454. I know that the ratio is either 3.73 or 4.10. I allready have 3.73 in my 10 bolt on my 87 K5. Also, the 14 bolt should just be a pop and swap. Right? anyways, the guy told me $150.00 bucks for the thing and if the ratio is 4.10 I should probably jump on it. Any help would be appreciated.
     
  2. Topdown

    Topdown 1/2 ton status

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    what is the casting number stamped in it? is it all stock? you could do a quick check if its off thr ground, line up the output shaft, grab a lug and spin it one complete rotation. it should spin the output shaft more than complete turns (just barely) if its a 4.10 and less than 4 complete turns if its a 3.73.
     
  3. zakk

    zakk 1/2 ton status

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    you need to pop the cover anyways to look at the gears. the ratio will be stamped on the ring.
     
  4. Lance

    Lance 1/2 ton status

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    Yup, what they said If it is in the vehicle jack the vehicle up and spin the pinion yoke on the rear diff one full turn. More that 4 full turns of the tire it is likely a 4.10, less than 4 full turns it is likely a 3.73. This isn't an exact science but since most civilian units came with these two gear ratios with some exception it will give you a pretty good idea.

    I suggest you could pull the cover and look at the numbers stamped on the ring gear. The first number should be either a 10 or 11 (for the number of teeth on the pinion) the second number is 41 (the number of teeth on the ring gear). Divide and you have your gear ratio. Plus it is a good idea that way you can see the condition of the fluid, gears and gov-lock (if any).

    This is a semi-floating unit? I could be wrong, but I didn't think Subs came with full-floaters. If so, while it is a good upgrade over the 10-bolt, it seems rather expensive to me. I would suggest locating a stronger and (in my opinion) more desirable full-floater rear end.

    It should just bolt up, but take some measurement from the center of your spring perches and compare them to the measurements on his axle to make sure.

    Good luck,

    Lance
     
  5. BIG B.

    BIG B. Registered Member

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    If the ratio is 4.10, is $150.00 a good price? He did say the the front end was a 10 bolt. That means that the ratio's would have to match. Would it be better for me to get them both for $300.00, instead of regearing my front 10 bolt. The guy is running 38" super swampers so it's gotta be 4.10.
     
  6. 87BrnRsd

    87BrnRsd 1/2 ton status

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    [ QUOTE ]
    If the ratio is 4.10, is $150.00 a good price? He did say the the front end was a 10 bolt. That means that the ratio's would have to match. Would it be better for me to get them both for $300.00, instead of regearing my front 10 bolt. The guy is running 38" super swampers so it's gotta be 4.10.

    [/ QUOTE ]
    First of all, $300 for both is cheaper than a re-gear for just one. $300 will just barely get you the parts for the re-gear, not to mention the labor. Second, just because he has 38 inch swampers doesnt mean it is 4:10. People do some strange things some time. Never assume with parts that need to be exact such as gear ratios. The best way to tell is to pop the cover. Stamped on the ring gear will be "GM, then a long vin number, then the ratio: i.e.- 10 41 (which would be 41 divided by 10 so it would be 4.10), or whatever the numbers are, then there will be 2 more numbers like 7 79 which means it was made in july of 1979. That is the best way to tell the ratio.
    -Harrison
     
  7. Lance

    Lance 1/2 ton status

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    So is it a full floater? That is the first question that needs answering.

    Assuming it is a full-floater, $300.00 for the pair isn't a bad price, especially if you consider the labor cost to re-gear your front will be between $300-400 not including the parts. The front will probably be 8-lug to match the rear as well, that is if it is a full-floater rear so you are saving yourself some money there as well. For that matter, $300 for a 10-bolt front and semifloat 14-bolt isn't a bad of a deal. The full-float is just more desirable.

    Several people on here have given me this advice in the past and it has saved me some headaches so I'll pass it on. You have to decide what your goal is for the rig and stick to that plan. If not, you'll waste both your time and your money and will never be happy. Let us know what your plan is and people can give you examples from there own experiences.
     
  8. Zeus33rd

    Zeus33rd Smarter than you GMOTM Winner

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    It could be 3.42, 3.73, or 4.10. Subs did come with full floaters. Best thing is to take a ratchet with a 9/16's socket with ya, and pull the cover. Take a gander at the shape of things in there, and check the numbers on the ring gear to confirm ratio. $150 is a decent price for any 14b FF, even better if it's 4.10. And yes, if you can get both axles for $300, then do it. It's alot easier and cheaper to swap two axles than it is to regear one. And if it's from a Sub, it will bolt right in. All ya need is a conversion u-joint. Is it 8 lug?
     
  9. kennyw

    kennyw N9PHW Premium Member

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    [ QUOTE ]
    So is it a full floater? That is the first question that needs answering.

    [/ QUOTE ]
    If it is original to the '84 burb it is a FF. SF 14 bolt did not come out until 1985. on all 3/4 ton trucks and burbs /forums/images/graemlins/thumb.gif

    Also pull the cover and check the condition of all the gears for both the front and rear axles before laying down any cash /forums/images/graemlins/thumb.gif Nothing would be worse than getting them home and finding a problem and it's not likely you could get your cash back. $300 is a great deal for a matched set too /forums/images/graemlins/thumb.gif
     
  10. Lance

    Lance 1/2 ton status

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    [ QUOTE ]

    If it is original to the '84 burb it is a FF. SF 14 bolt did not come out until 1985. on all 3/4 ton trucks and burbs /forums/images/graemlins/thumb.gif



    [/ QUOTE ]

    Thanks, I didn't know that!! I thought all the knewer body-styles ('81-on) had 14SF.

    /forums/images/graemlins/thumb.gif
    Lance
     
  11. BIG B.

    BIG B. Registered Member

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    The guy is going to check for me later on today when he gets home from work. I won't be able to look at until tomorrow maybe. You all have been very helpfull. This is the best site ever. Is there anyone in the San Diego area who would be willing to help me with the swap if the deal goes down? I will pay for beer! In the mean time I will keep my fingers crossed.
     
  12. 87BrnRsd

    87BrnRsd 1/2 ton status

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    That is a pretty good price. I paid $550 just for my rear 14ff. Now, before you all say I got ripped off, it has 4.56's, a detroit, and is brand spanking new from GM! This thing has never even seen a truck. The spring perches still have the factory paint on top of them. Dont ask me where I got it though, because it came from a friend who only had 1. /forums/images/graemlins/eek.gif Lucky me. /forums/images/graemlins/rotfl.gif
    -Harrison
     
  13. BIG B.

    BIG B. Registered Member

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    One quick question. My rig is mainly a DD. Is a 14FF to much for a DD. I plan on doing some light wheeling from time to time and was thinking that a 14 bolt could give me some extra security. What do you guys think?
     
  14. Lance

    Lance 1/2 ton status

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    Mine is a DD, a weekend warrior. I have a d60/14blt in mine and I did it for the since of security because I can't afford to be w/o a vehicle come Monday morning. Is it overkill? Probably, but I'm still glad I did it and (knock on wood) no failures from them yet.

    If nothing else, you'll probably want to lift your truck and put bigger tires on it in the future, the gears alone in those axles is worth the swap in my opinion.

    Good luck,

    Lance
     

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