4.88 in BJ74

Discussion in '70-Series Tech' started by vsh150, Nov 7, 2005.

  1. vsh150

    vsh150

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    Hello , im new in de forum. I have a couple of bj74 diffs with mechanical lockers and 4.11, my cuestion is if i can use an aftermarket set of 4.88 R&P . You now if is possible?


    SALUTES

    PD: Sorry but my english is no good
     
  2. beanz2

    beanz2 Moderator

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    Welcome to the forum :cheers:

    I have a set of 4.88 Precision Gears with my cable diff locks. So it is possible, but I am not too happy with the highway engine speed it provides. With 35" tires I am turning 2800 rpm. One day I will go back to 4.11 gears again.

    Dave
     
  3. Tonito

    Tonito

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    hi dave,
    u wanna drive 35" tires with 4.11 gears ... in a car powered by a 3B or a 13B-T?
    I can't imagine that this setup can move the cruiser ... i allready wondered about the loss of power with the 255-85R16 tires (3B-II and 4.11 gears).

    greetingz
     
    Last edited: Nov 8, 2005
  4. beanz2

    beanz2 Moderator

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    Mine has a 1HDT ;) I usually start in 2nd gear as 1st gear is useless on the road...

    Dave
     
  5. Tonito

    Tonito

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  6. dieselbigot

    dieselbigot

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    Dont do it! I had 4.88's in my 3BT BJ70 with 34's and like Dave, hated them....(although Dave, when I drove your Troopy I must say I did'nt mind the 4.88's...mind you I only drove it a short bit)

    If you have the power like Dave, 4.11's will work...if you don't, I'd go 4.56...this is what I run with 35's (and Marks 2.8 / 0.92 Tcase gears) and it's about perfect
     
  7. Tonito

    Tonito

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    Thats what I planed ;)
    I think the 4.11's are quite nice for the 255-85s, but not for bigger tires. For the tires I want (34.9-9.5R15 Swampers - maybe next year) I should change to 4.56's ... but first of all I have to lift the cruiser a bit (whats about a 2" bodylift? The leafsprings (SUA) are probably 2-2.5" higher than factory leafs).

    greetingz from germany
     
  8. Tapage

    Tapage Club 4X4 Panamá SILVER Star

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    Que onda loco .. !

    Short answer yes, you can ..

    Long answer, the 4.88 gears it depends a lots of your engine, type of vehicle ( towing or expedition ) and your off road target ..

    I thought 4.88 with H42 or H41 are not a good idea, a least you plan run over 37" tires ..

    date una pasada tambien por un foro chileno muy bueno ..

    http://www.twistedandes.com
     
  9. tlcruiserman

    tlcruiserman SILVER Star

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    Ok I will have to add my 2 cents. I run 4.11's in several of my 70's with turbos and they are great off road and up on the hiway, no issues. I concur with Brett that 4.88's with 35" and 3b turboed are too low, I have that setup in my BJ42 with the H55f and it is always the wrong ratio off-roading. I would not recommend anything lower that 4.56's.

    Cheers,

    Michael
     
  10. vsh150

    vsh150

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    Thanks for yuors answers , the 4,88 is for running 37"s in a rig for offroad use only with a five speeds trans.

    Salutes


    PD: Tapage creo que conozco ese foro... jaja saludos amigo.
     
  11. lloyd_lluvbullet

    lloyd_lluvbullet

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    hi all :)

    I have a 1HZ Turbo Intercooled (CT26 Toyota Turbocharger) 4.2L I-L 6 coupled to R151F & running 7.50-16 knobbies (31" tires).


    I plan to upgrade tire size to 35"-11.50-16" Simex Centipedes with the R&P ratio lowered to 4.88s.


    Question:

    1) Would this be too harsh for long haul drives on the freeway?

    2) I plan to lower my stock TC ratios in the near future to increase overall crawl ratio to at least 60:1 & beyond, will this plan allow me to increase R&P ratio to 4.56 instead to provide better driveability on tarmac?

    3) Anyone knows how to calculate actual RPM to decide if R&P needs to be lowered or geared higher?


    Thanks!!
     
  12. lloyd_lluvbullet

    lloyd_lluvbullet

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    forgot to mention, the setup mentioned in my last post is on a 1989 BJ60 otherwise known as a HZJ60!! :grinpimp:
     
  13. Greg_B

    Greg_B

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    I have some Marks 3:05-1:08 gears in my BJ60 with 35" tires. I did have 4:56's and it was too low for sustained highway driving. 4:11's now, it is it just about right.

    I have run 35" SSR's on my BJ74 (13BT) with 4:11's. It is fine on pavement. You do notice the engine working more, but imo still fine. I most situations off road it is fine. On rocks it is not low enough. Some 4:11's and Marks gears would make things nice.

    I daily run 255/85R16's on the BJ74, and it is fine in both situations with the 4:11's.

    Of course the option of more gear is always better in low...:D

    hth's

    gb
     
  14. Tapage

    Tapage Club 4X4 Panamá SILVER Star

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    Actually mi HJ-60 with 2H engine running 37" MTR with 4.56 and Marks underdrive gears, givenme a 112 km/k ( 77 mph aprox ) ( Garmin info :D ) @ 2500 rpm 5ft ( off course H55F ) speed ..
     
  15. lloyd_lluvbullet

    lloyd_lluvbullet

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    hi Greg

    I was jus thinking about Marks Gearmaster low gear set...how easy is it to install them? My BJ60 is using a R151F 5-speed manual transmission & 1HZ ( custom turbo intercoooled) from a 2001 HZJ79 series Land Cruiser pickup.


    Was it a straight bolt-in? If I don't intend to run 35" or taller tires in the long-run, would the 3.05:1 Low & 1:1 High ranges be suitable then..., assuming I stuck with either 33" or 34" (available in my country Malaysia) tires? (stock R&P of 4.11)


    OR


    Run 34"-11.50-16" tires, 4.56:1 R&P, turbo-intercooled 1HZ & Marks 3.05:1 & .92:1 overdrive High range




    OR


    same as above but Marlin's single case 4.70:1 or 'doubler' case



    hope you can share some feedback on this since you've ran 4.56:1 R&Ps before.
     
  16. Tapage

    Tapage Club 4X4 Panamá SILVER Star

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    I'm not Greg ;) but you be adviced about the diferences between Split Cases BF1A and HF*AV series transfer cases ..

    In the firs ones, common mated to H55F and H42 tranny, you can apply the underdrive or overdrivbe marks gears .. but in the other ones, only the gearmaster to reduce only the low gear.

    Anycase I thought if you have HF*AV series transfer case with 4.11 you can go with 3.05 low set to get real low gearing..

    But if you have BF1A splitcase .. with the underdrive marks gears and 4.11 you don't need more gearing to run with plenty of power 34" tires.
     
  17. beanz2

    beanz2 Moderator

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    Marks new 3.115 gearset only works if you have HF2A (the full time, non viscous coupled.) HF1A and HF2AV gearsets are not out yet.

    But you can get their Cruiser Crawler gearbox to fit behind the transfer. 3.05 ratio on top of your factory ratios.

    Dave
     
  18. Greg_B

    Greg_B

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    Hello!

    I think it all depends on what you are going to do with your truck...

    How's that for not answering :D

    I believe I would be tickled in most situations with the 3.05 and 1.08, 4:11's, and true 35's on my BJ74. I have never run 4:56's with the stock gearset so can offer no opinion with that set-up.

    I think as a general rule of thumb the idea is to gain as close as you can to your stock ratios in high range, as you up the tire size and increase the ratio in the diffs. Having the turbo on your 1HZ will certainly give more latitude.

    If I were going to use one of Marlins options I would not bother doing the gearset in the t-case as well. I am not even sure you would need the 4:56, but it may well give better ratios and a better drive.

    Where did the gear ratio tables ever go when the TLCA new website replaced the old one?

    hth's

    gb
     
  19. Greg_B

    Greg_B

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    Ooops. I never answered this one, sorry.

    It is supposed to be a couple banana job. I have not done it. I had an H55F from a parts BJ60 that needed the tranny and t-case rebuilt. I took it, the rebuild kits, and the gearset to Tony at AllToy in Kamloops and had it all done at once. The 3.05 required a small portion of the case to be ground away. No building up on the outside was needed.

    I know a few here have done the swap, and perhaps they will speak up.

    hth's

    gb
     
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