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Thread: Gearing change questions - 1966 bus on Loadstar 1600 chassis, with RA-30

  1. #1
    Join Date
    May 2013

    Default Gearing change questions - 1966 bus on Loadstar 1600 chassis, with RA-30

    Hello. First-time poster to this forum. Would really appreciate feedback from people who know the gearing issues on the old Loadstar 1600s (1966 Int'l shorty bus - Superior Coach body - standard Loadstar running gear, 304 gas motor, T-35 trans.). Like many people's trucks, this one is geared WAY to low to use on modern highways (I have now confirmed I have the 6.67 gear set). When I bought it years ago, I didn't anticipate this issue - that it would be literally un-usable for traveling, with the current gearing. I am going to have to change-out the rear ratio.

    I know the "commonest" taller ratio is 5.29 - and this is available. But this still yields 3,300 RPM at 65 MPH (I live in California; go less than 65 on a freeway (or 50 MPH with my current gears) and you will be killed from behind; average interstate highway speed in this state is 80 MPH). 3,300 RPM seems unnecessarily high for 65 MPH, my practical maximum speed perhaps. (My bus is stripped, no seats, will not be carrying more than several humans, is only 21 feet long, and will be carrying much less weight than the usual bus of this vintage; but I don't know the exact weight yet.)

    There exists a 4.78 gear set for the RA-30 differential. I have a parts diagram that lists this ratio, with it's parts number, p/n 591934C91. I have also seen p/n 1653808C91. The guy who will do the ring and pinion swap says he's seen a 4.78 in the front axle of a 4WD vehicle, but hasn't seen it in a 2WD rear. This is not to say that it wouldn't drop in (after all, the exploded parts diagram mentions this ratio for a "Rear Axle") - but, there are some uncertainties. The 4.78 gears would yield almost exactly 3,000 RPM at a road speed of 65 MPH. This 3,000 RPM seems neither excessively high, nor excessively low, for 65 MPH in a vehicle with a significant amount of frontal wind resistance.

    What do people think about this proposition? Is 3,000 a reasonable target RPM for 65 MPH in a shorty bus with a 304 gas motor (listed at 160 HP)? Does anyone know of the use of the 4.78 ratio in the rear? Is there any reason to think that it would pose a technical issue for the rebuilder? Where, who, from what company...should I look for this ring-and-pinion set? It seems much less available than the common 5.29 ratio. But 4.78 would seem to yield a less noisy and more fuel-efficient RPM at 65 MPH.

    I would be grateful if any knowledgeable person could comment on these questions, or provide other new or different perspectives. Thanks in advance.

    Dr. Steve

  2. #2
    Join Date
    Aug 2017


    I would love to see pictures of your bus please I have the same one it sounds like 1965 loadstar 1600 shorty converted bus camper with a 345 engine thanks

  3. #3
    Join Date
    Oct 2009


    Yes this rpm range is reasonable for the 304. If there is a problem getting these gears to fit, then taller tires are the next best thing. I assume it has either 8.25 x 29 or 9.00x20? on a dayton spoked wheel? There are tubeless rims available to fit that use a 10.00x 22.5 tubeless tire. Radials make the steering so much nicer, less wandering.

    I had a 1600 with 345 and two speed rear, 5.85 I think was high, might be wrong about that as 70 was reasonable for cruising, however did also have the 22.5 tires. Now have a 1971 1700 bus with the 392, and 5.13 rear, under restoration so have not driven it yet.


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