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Technical 235/T5 rear gears

Discussion in 'The Hokey Ass Message Board' started by KyleBern61, Oct 30, 2021.

  1. KyleBern61
    Joined: Nov 24, 2011
    Posts: 14

    KyleBern61
    Member
    from Tulare, Ca

    For those that are more experienced, I need some input on what rear gears to run in my 46 Chevy 3/4 ton. I have a 235 and S10 T5 transmission. I’m on the fence between 3.73/4.10 rear ratio. I’ll be using a 10 bolt rear end from a Chevy Colorado which was offered in both gears. I plan to run a 29” tire or close to it. I put the data into the calculator on Tremec’s website, but for those of you with real world experience what looks to be the better setup for highway (70mph) and in town driving?

    FB784DED-F9F7-44EE-B4A2-027A435A8E69.png


    C631204D-BA2D-44FA-83D8-E14F306C4031.png
     
  2. ERguitar
    Joined: Aug 26, 2018
    Posts: 149

    ERguitar
    Member

    Not a ton of difference between the two. Without knowing any specifics on your motor I'd say 2500 @ 73 mph sounds about right. If you're truly going to predominantly use the car for high speed (70 mph plus) driving the 3:73 gear might be a good choice otherwise I'd go with the 4:10 ratio for a little more scoot.
     
    samurai mike likes this.
  3. brokenspoke
    Joined: Jul 26, 2005
    Posts: 2,925

    brokenspoke
    Member

    My choice is 3.55, if most use is hwy
     
  4. Remember that 1st gear is very low.If you go 4.10 it will be almost unuseable. I have the 3.76 1st with 3.70 rears,and I only use it to start on hills.If its flat where you live I would go 3.70 in the rear.If you find yourself on the highway in mountain country the 4.10 might be better.
     

  5. KyleBern61
    Joined: Nov 24, 2011
    Posts: 14

    KyleBern61
    Member
    from Tulare, Ca

    Ya, I know I’m probably splitting hairs. I just want to make sure that in the process of getting it to run well on the highway I don’t end up have a 5th gear with no pull. Appreciate your input.
     
  6. KyleBern61
    Joined: Nov 24, 2011
    Posts: 14

    KyleBern61
    Member
    from Tulare, Ca

    It’s all flat farmland around here. Truck has 4:56 gears now and like your saying it starts out in 2nd, no use for 1st gear unless I need to climb a wall. This is helpful advice, thank you.
     
  7. ERguitar
    Joined: Aug 26, 2018
    Posts: 149

    ERguitar
    Member

    First gear is going to be low regardless of which of the two ratios you choose. @2500 rpm there is only 1 mph difference or so. I think with 29 inch tires and a 4:10 ratio your still going to find yourself using 4th gear the most in 55 mph scenarios. These old motors need to turn some rpms to be happy. Don't be afraid to wind er' out a bit.
     
  8. tiredford
    Joined: Apr 6, 2009
    Posts: 546

    tiredford
    Member
    from Mo.

    I have a T5 in my 2300 lb. roadster. It has a Ford 200 motor with headers and mild Comp Cam. Same .72 fifth gear. I changed to .83 because of the no pull in fifth you mentioned. oh, my rear gear is 3.92 and 29 in. tire. It runs at 2500 RPM @ 70, which is where the little 200 is happy.
     
  9. Wish I could give some better real world help, I have a 235/T5 in my 52 Chevy Ute with a 3.70 rear gear (56 car rearend for the open drive). Haven't got it done enough to have freeway experience. But I can say that 1st gear winds out very quick as the S-10 T5 have really low 1st gear ratios. I can easily start in 2nd gear with the limited driving just around my neighborhood up to this point. I think if your 235 is stock or near stock, go with the 3.73, it will be happy at the lower rpm. If you have the 235 built up more, then 4.10 would work. Either way you will probably not use 1st gear all that much.
     
  10. 52HardTop
    Joined: Jun 21, 2007
    Posts: 969

    52HardTop
    Member

    My 52 Hard Top has a 54 235 and an S-10 T-5 Tranny. Yes it has the lower 1st gear. I do have 373s in an early Nova 10 bolt rear. I do use 1st gear a lot. I like to hear my dual exhaust with resonators, rap with that classic 6 cylinder exhaust sound. I can cruise on the highway and have no trouble keeping up with traffic, if I want to. As for the 5th gear, my engine will still pull in 5th with no trouble. I find I want the 5th gear as I'm used to the engine sound at a reasonable rpm and when it starts to sound like it wants another gear on the highway, I just give it to her.
     
  11. gimpyshotrods
    Joined: May 20, 2009
    Posts: 19,128

    gimpyshotrods
    ALLIANCE MEMBER

  12. anthony myrick
    Joined: Sep 4, 2009
    Posts: 8,915

    anthony myrick
    Member

    Imma gonna use 355s with mine
    But I’d go 373s out of the choices you stated.
    The s10 t5 has a low first gear. That’s why I’m going 355s
     
    pprather likes this.
  13. KyleBern61
    Joined: Nov 24, 2011
    Posts: 14

    KyleBern61
    Member
    from Tulare, Ca

    I appreciate the feedback from everyone. Truck is currently in the build phase. I bought a S10 T5 last week with a 10 spline Jeep input shaft. Bought a 235 that ended up needing some machine work. Stopped by the machine shop yesterday and won’t be able to
    get in until December, but he seems to do really good work so I’ll be patient. I think I’ll go with the 3.73 rear end. I commute to work about 30 miles each way and plan on taking this pickup on the road every chance I get.
    BB400511-B7DB-49C5-A3F0-D1666CC3CA99.jpeg
     
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  14. jimmy six
    Joined: Mar 21, 2006
    Posts: 10,264

    jimmy six
    ALLIANCE MEMBER

    Just a guess but I’m thinking 73mph in OD with a 95 hp engine is going to be tough. I’d pick the 4.11’s Your pushing a brick near 4500 pounds. 3.73’s would be worse and you may never see OD. Nice thing is when you upgrade the engine at some point a ring and pinion will be easy.
     
  15. Gofannon
    Joined: Feb 8, 2007
    Posts: 721

    Gofannon
    Member

    If that's the 6 lug 3/4 ton rear you should be able to drop a 3.90 from a 55 to 62 1/2 ton into your housing.
     
  16. KyleBern61
    Joined: Nov 24, 2011
    Posts: 14

    KyleBern61
    Member
    from Tulare, Ca

    Mines a 3600. I believe all 3/4 tons were 8 lug, that’s what I have. HO52 rear end with 4:56 gears. I know the later C20 pickups ran the same rear end and offered a 4.11 gear set which would be a direct swap, but there next to impossible to locate and k very desirable. I’ll be using a half ton front axle and spindle to take advantage of more available brakes, and then a Colorado rear end..
     
    Gofannon likes this.
  17. fastcar1953
    Joined: Oct 23, 2009
    Posts: 2,701

    fastcar1953
    Member

    3.42 would be my choice.
     
  18. Gofannon
    Joined: Feb 8, 2007
    Posts: 721

    Gofannon
    Member

  19. motion guru
    Joined: Oct 18, 2009
    Posts: 159

    motion guru
    Member
    from yacolt, wa

    I am running an A833 OD with the same OD ratio as the T5 with 3.73 gears and 30” tall tires. My truck is a half ton and I am running a high compression 270 GMC bored to 292 running dual carbs and dual exhaust. It runs fine at 1850 RPM at 60 mph, but I often wish I had gone with the 4.11 gears.

    If I had a near stock 235 with the heavier 3600 series truck shifting a T5, I would rather have the 4.11 gears.
     
  20. anthony myrick
    Joined: Sep 4, 2009
    Posts: 8,915

    anthony myrick
    Member

    Ran my 235 with and 355 gears.
    Ran 60mph all day long. Had plenty of torque but really could have used an OD for interstate cruising.
     
  21. KyleBern61
    Joined: Nov 24, 2011
    Posts: 14

    KyleBern61
    Member
    from Tulare, Ca

    Gofannon likes this.
  22. HotRodWorks
    Joined: Dec 6, 2005
    Posts: 342

    HotRodWorks
    Alliance Vendor

    @KyleBern61
    Here are a couple of data points you can add to your information:
    I have a 235 ci, 9:1 compression, dual carbs, Fenton headers, HEI in a 3000 pound 51 coupe. It runs 75 mph in the 1/4 mile.
    I've run (2) S10 T5 transmissions. One is a 4.03 1st gear with .86 OD. The other is 3.76 1st gear with .72 OD. I have 26.5" diameter rear tires.
    Either one is ok in 1st. It's a little low, but I can run it up to 15-20 mph in 1st which is 2500-3000 rpm.
    We run 80 on the interstates around here which is about 2850 with the .86 OD. It has no problems keeping up with traffic or climbing moderate hills. I did feel that it was buzzing too high, so I tried the .72 OD. That's about 2350 at 80 mph. I put a vacuum gauge on it to see how it was working. It was ok on level ground, but with any moderate hills the vacuum would drop as I had to give it more throttle. It just doesn't have the horsepower to pull it like I'd hoped. I put the .86 OD back in it. It buzzes higher, but it is making more horsepower and will go anywhere easily at 70-80 mph.
     
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  23. jimmy six
    Joined: Mar 21, 2006
    Posts: 10,264

    jimmy six
    ALLIANCE MEMBER

    ^^^^Real experience is always good. HRW you don’t say what it’s in and aero at 80 means a lot.

    A 46 3/4 ton stake bed is definitely not a car and has a lot of wind resistance and was meant for 50 mph when new in its day.
     
  24. My 51 Chevy pickup has a 235/T5 the rear is a gm 12 bolt with 3:32 gears. Pulls nice off the line and cruises 70mph all day long
     
    HotRodWorks likes this.
  25. HotRodWorks
    Joined: Dec 6, 2005
    Posts: 342

    HotRodWorks
    Alliance Vendor

    It's in a Coupe. You're right, it's a pretty big brick at 80, so it needs rpm to make enough horsepower.
     

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