3:55 ARE available for the 8.5" 10-bolt

Discussion in 'Got gears?' started by BrianTrick, Aug 28, 2017.

  1. BrianTrick

    BrianTrick Brian Trick

    For many years,people have wanted the 3:55 ratio for the 8.5" 10-bolt. Quick Performance has some in stock. They are made by US Gear. They are in the mid-$200.00 price range,but they are a nice gearset,and in my opinion,one of the best ratios.
    I will be doing a few installs with them soon.
     
  2. hugger

    hugger Well-Known Member

    Be nice if they would do some 3.64's
     
  3. BrianTrick

    BrianTrick Brian Trick

    Years ago,I wanted something like that. The closest I could get was the Richmond 3:70's. I'm not sure if those are still available or not. They made both 3:70 and 3:73.
     
  4. hugger

    hugger Well-Known Member

    $750 or however much they are from Fabcraft is little tough to swallow
     
  5. BrianTrick

    BrianTrick Brian Trick

    IMG_1809.JPG IMG_1810.JPG IMG_1811.JPG IMG_1812.JPG IMG_1814.JPG IMG_1815.JPG IMG_1813.JPG These are in the $240-$250.00 range.
    Here they are:
     
  6. monzaz

    monzaz Jim

    really is that necessary to go from 3.42 to 3.55? Doubt your going to notice a difference at all.... your getting less teeth in the 3.55 (11 x 39 )compared to the 3.42 (12 x 41)and the reason for the swap by GM
    All the newer ratios are MORE teeth ... IE --- GTO 3.46 ratio is 45 x 13 ...and smaller teeth more touch points etc. .... just like why we do not see coarse spline low count teeth to fine spline high tooth count axles ...... right?
     
  7. monzaz

    monzaz Jim

    If the gear is just a better made quality gear I GET IT... do what you need to do. :)
     
  8. Bens99gtp

    Bens99gtp Well-Known Member

    I really don't think there would be more contact area......each tooth has the same surface area and I would think there would be very little overlap contact between teeth while going from one to the other. On the other side to that slice of bread, with more teeth in the same area you have less mayerial in each tooth as compared to fewer, what is stronger, a thicker tooth or thinner?. I see both sides cause if you have more contact area the pressure is more distributed. The question us is there more contact area at any one time as the gears rotate?.


    I know we had 3.73 Richmond's, broke 2 sets, but 3.70s in from the same company, no more breakage. I set all 3 sets up, to as identical preloads, depths, and lash as the shims would let me get. Both set sheared the teeth off the ring gear. The 3.73 were 41/11 the 3.70 were 37/10.
     
  9. BrianTrick

    BrianTrick Brian Trick

    Interesting find Ben. I ran my 3:70 for quite a while. 10:90's@122 range. I then stuck that rear in another car with stick,running the same range,and it is still going 20 years later.
    The finish on these gears is definitely better than the cheaper crap that is being pawned-off these days. Maybe not quite as nice as the Italian Motive line,but still very nice.
    Yes,one would think that most would just pick the 3:42,but the normal dilemma I see is that the customer doesn't feel that 3:42 is quite enough,and 3:73 is too much. Now there is something in the middle. Maybe they will sell like hot cakes,maybe not. It's just nice to have more options.They would work nice with a big block and overdrive,like a 2004R or 700R4
    For those that need more tooth-contact,the DANA 60 has 2 full teeth connected.
     
  10. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    I have 3.73 gears. With a 28" tire, the effective ratio is 3.54. I can change ratios just by changing tires, so can anyone else.
     
  11. BrianTrick

    BrianTrick Brian Trick

    Yes,you can,but some do not want to do that. Some have a certain tire that they want to run,and some are like rainman when dialing-in the cruising rpms.
     
    300sbb_overkill likes this.
  12. 300sbb_overkill

    300sbb_overkill WWG1WGA. MAGA

    Or a Wizard! :p:D:D
     
  13. Bens99gtp

    Bens99gtp Well-Known Member

    Tire size is easily over looked, a buddy's Mustang was running 4.10s with 25" tires going out the back door around 8000, over the years he went up to 26, the a glide from 3 speed, then to 28, and was not liking his 60 times or going through the top at 7000, a change to 4.88 and he's back to goos 60s and 8000 up top again
     
  14. BuickV8Mike

    BuickV8Mike SD Buick Fan

    Can you change only 4th gear to provide help on the freeway for numerically challenged folks?
     
  15. BuickV8Mike

    BuickV8Mike SD Buick Fan

  16. BrianTrick

    BrianTrick Brian Trick

    It's better if you are starting from scratch,and map everything out. What usually happens,is that a car gets built along the way,and the rear is usually last. Then they want to gear it to everything else. I had a customer that had all the mathematics figured-out for his Richmond 5-speed and his 455. We couldn't split ratios,so he actually ordered a different 5-spd,with the correct ratios that have him what he wanted with his rear gear. Did it drive any different? NO.
     
  17. monzaz

    monzaz Jim

    Got to say there has to be more to the story than the ratio tooth count causing the broken teeth..... Sure seems like you would have to be doing something wrong with 2 broken gears and millions of other racers with faster or powerful cars can certainly keep their gears running. How long did it take to break these gear sets. ?? :)

    Jim
    J D
     
  18. oldsmobiledave

    oldsmobiledave Well-Known Member

    I think the 3.55 is an excellent choice if you currently have a 2.73-3.08-3.23 and want to move up but can't decide between the 3.42 an the 3.73. The 3.55 is not worth changing to if you already have 3.42 or 3.73 since a tire size swap will achieve most of that.
     
  19. Bens99gtp

    Bens99gtp Well-Known Member

    Each set took a few years of every weekend racing. I found it strange too. At the time we were going mid 11s, gears should gave never been an issue. There were set up correctly, I'm not a rear axle pro, but I set up 10 or 12 a year on average for the last 15 or so years, never had another setup cause me any issues. Will I say it perfectly in specs, no, will I say it was a close as I could get it with the shims I had in the install kit and be within 1 or 2 thou. Yes, should a pinion depth 2 or 2 thousands off break teeth off the RI g gear, I wouldn't think so,

    The 4.1 set we ran b4, the 3.7, and the 4.56 I use for 1/8th race are all still together. I don't know what happened.
     
  20. ken betts

    ken betts Well-Known Member

    What happened , you went racing. When I ran my 72 Stage 1 in F/SA I had a professional set up a 4.66 rear. First run off the starting line blew the rear end up. The next day I put my 70 rear back in with 4:78's. Should have traded my 12x28" cheater slicks with some 9x29 or even 30" probably would have gone faster!
     

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