Transmission, mixing oil, and tran/3rd member identify

Discussion in 'Engine/Drivetrain' started by aseq, Nov 15, 2014.

  1. aseq

    aseq Member

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    87 2wd, Carb, Longbed xtra cab
    I have a rebuilt transmission, 5 speed. The original one was 5 speed and had a cast iron body, I think, it certainly had that look. However I had a shop replace it so I never took a close look. The gearing was more truck like, and it would rev quite high in 5th above 70 mph.

    The rebuilt transmission I believe is a w55 or w56, it has more of a car gearing (higher?) ratio, with lower rpm at highway speeds in 5th and 2,3 and 4 being geared closer together (I think). Also first gear has a slightly higher ratio (I hope I didn't get the naming mixed up).

    There is a slight problem that pretty much started a year or so after it was installed, where the gears make sort of a rattling sound at a certain rpm range if you accelerate more than moderately, in 2nd gear it's between about 20-25 mph, in 3rd between 30-40 mph etc. It'll disappear soon once you go above a certain speed and rpm range, but it's annoying.

    I managed to make it quieter by mixing about 60% redline MT90 with 40% redline 75w140ns gear oil. But it's not totally gone. Since I have driven with it for about 5 years I doubt it's anything serious, but any ideas what could cause it and how to fix it would be helpful.

    I suspect a new rebuilt transmission (or rebuild this one) would be the only real option. I also think it's the actually gears that make the noise, there is none of that whining bearing sound the old transmission started to develop and it shifts well.

    I attached a photo which may help identifying it, as I said I suspect it's a w55 or w56, it's all aluminium.

    I am thinking of possibly changing the 3rd member in order to allow a bit more acceleration, the new LCE street head, cam and header can use the higher rpm ranges. I don't care much for driving above 70-75 mph, in 5th it's only barely hitting the higher HP and torque at 85 mph.

    Any idea what the ratio would be in the differential? It's an original one, though I suspect it came from an 89 model since it has that year painted on it (maybe a junkyard piece). I can probably figure it out by turning the axle and see how many times it turns for the wheels to turn once.
     

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  2. White Trash

    White Trash Toyotaholic

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    Sounds like you had an old w50 and replaced it with a w55 or possibly a w58. There aren't a whole lot of easy lower geared options out there for a 7.5" axle that you likely have. It's easily identified by the drain plug location on the bottom passenger side of the housing. The 8" that came in carb'd 4 speed (G code) trucks has factory options from 3.07 to 4.88 so you can go either way from what is likely 3.42's in your axle now. The 8" has the drain plug on the lower drivers side of the housing. I'm running a w58 with 4.56's and 25" tall tires on my 90 and I must say its a fawking hoot to drive now and it'll still go down the freeway just fine. It's topped out a bit over 100 mph but I'm ok with that. :d
     
  3. first80toyota

    first80toyota Addict

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    Lower gears are harder to find, but they are out there..

    I'm running a w55 with factory 4.11 gears and stock size tires.. Pulls good and tops at about 115-120mph
     
  4. aseq

    aseq Member

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    Good info, thanks. The drain plug on the axle is at the bottom passenger side yes.

    The other week I got around replacing the axle oil as well, and I used redline 75w140. Considering I live in CA it should not be a problem. Whether it actually makes a noticeable difference I don't really know. Since I have replaced the bearings a few years ago it's not been noisy to begin with.
     
  5. aseq

    aseq Member

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    Back in May I ordered a rear differential on ebay from a 1991-1995 Toyota Previa, it was from a naturally aspirated Previa so it has a 4.30 gear ratio (the super charged Previa has 3.5 or there about). Since this was a 7.5 differential it fit perfectly. Judging from the lack of wear on the teeth and how quiet the bearings sound and how run out seemed to be within spec it had not been used a lot. Maybe 50K miles? Either way it was way better than the diff that originally came with this truck (which, with the whole axle, seems at some point to have come from a junkyard, as it has the year 92 written on it), which had noisy bearings.

    The only problem this replacement diff had was a leaking front seal, which is to be expected and it was an easy fix without having to remove it.

    The ratio at 4.30 works very well with the w55 (or w58) transmission I suspect I am running. Helps a lot during commute which includes a mountain pass. Fuel economy is down about 1/4 I suspect. But it should improve once I replace the 75w140 diff oil I kept with 80w90.

    I think I may rebuild the old diff using 4.11 gear ratio and keep it as a spare, which could be the right compromise between power and decreased fuel consumption.
     

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