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I am in the process of installing a new ring & pinion with a 4.56 to 1 ratio into a rear from a 1987 Toyota full-floating dually. I am doing it for a friend and it's a good thing I'm not doing this at a professional level and trying to charge by the hour. For anyone who has never done a gear-change . . the worst part is the many times the differential must be pressed together and then pressed back apart. Why? The OEM setup has a factory-installed shim that has been ground to a special thickness to place the original pinion gear at the correct depth. This is critical and when right - the gear-mesh pattern is observed on the gears via marking compound. In an ideal situation it goes like this. You start by installing the new gear with the OEM shim and then see how far off it is. If lucky, you might have to press apart, and press back together 2-3 times until the mesh pattern is correct. In this situation? I had it apart, and then back together over 30 times and gave up. No matter what I did - pattern was awful and not usable. The OEM shim was .080" thick. I tried total depths of .30" up to .130" Doing this in small increments took two days, more or less with a few hours off, now and then. Note that Yukon Gear is the #1 maker and seller of aftermarket gears for cars and trucks. It is also what Marlin Crawler uses for all their Toyotas. So - in a fit of frustration - I contacted Yukon gear - by phone, email, and at their Face Book spot. It took two day to get any reply. The first one told me I bought the wrong gear-set and that all Toyota full-floating dually rears are the "V6" type rears. I told the guy he was wrong. He was. A so-called "V6" rear has four differential pinion gears (not to be confused with the ring & pinion). A often called "4 cylinder" rear has only two differential pinion gears. The guy at Yukon Gear did not realize that many if not most Toyota motorhomes have 2-pinion, "4 cylinder" rears. So, after nearly another two days - I got another reply from a different Yukon tech person. He now tells me that their replacement gears to fit a Toyota FF rear in a motorhome - if a two-pinion diff - will NOT fit without installing a conversion bearing. Nice of them to tell me that now! I did some research. Not easy since the OEM KOYO bearings that came in my Toyota rear do not cross-over to anything modern anymore. So had to measure them exactly - and do more research. It ends up that the new bearing that Yukon says I must use to make their gears fit - is .149" deeper then the original. So now I am even a little more confused. The install kit that I got with the gears came with a new shim pack that totals to .174". Some are .050", some .020", some .010", etc. Seems I can easily just add an extra .149" (or close) in shims with no need for the Yukon conversion bearing. I sent them a new question but God knows when I'll get an answer. I had to walk away from this thing for awhile a go plow some snow and help my kid with a home-school project. So we'll see what happens.

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I got the new ring & pinion set up correctly now. That is in spite of bad information from the company that makes and sells the new gears (Yukon Gear). Also in spite of some incorrect parts furnished by them. If anybody here decides to put a new ring & pinion in their Toyota motorhome - watch out ! There is much to know and that info is not likely to come your way easy. That is - unless after my recent confrontation with Yukon Gear - they make some changes.

I spent near 20 hours doing a job that should of taken 3 hours max. I wonder what happens if someone takes these new gears to a shop that charges by the hour and they get involved in such a mess?

Long story short. Yukon Gear no longer makes new ring & pinion gears that are an exact fit for a Toyota 8", 2-pinion differential. And note - that's what most of the rears are in our RVs - regardless if with 5 lug wheels and semi-floating rears, or 6 lug wheels and full-floating rears. What Yukon Gear sells now is a gear set made for Toyota 8" rears with 4-pinion gears. These rears are often called "V-6 or turbo" rears. Now - to make these gears fit a 2-pinion diff - a huge pile of shims must be used - OR - a conversion bearing that is thicker then the original. Also - the gear-set I bought came as a complete "install" kit. So it came with a new crush-collar. Note that most Toyota rears (with some older exceptions) cut corners and use these crush-collars as a time-saving assembly short-cut. Basically - it is a steel tube that MUST be longer then what is needed - and when you put over 400 foot pounds of nut-torque against it - it crushes and becomes shorter. The new crush-collar that Yukon Gear provided in the kit is too short and cannot be used. I wound up ordering a new one from Rock Auto and IT was correct.

Had I known all this information at the start of this - it would of been a 3 hour job, max. But since I had to figure this all out and deal with a lot of bogus information from Yukon Gear - it became a long and miserable process.

I won't post all the photos of how to do the job since I doubt anyone here cares. Here are a few at the end of the project. That including re-drilling the pinion flange so this 1987 differential can be used in a 1977 Toyota Chinook. And one added warning to anyone with a Toyota late 70s, early 80s. New ring & pinion might have different spline count and require a newer flange anyway.

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Yup Yukon Gear no longer shows the 4 cylinder ring and pinion on their website. It is still showing up on Marlin Crawler though. Maybe they just have a back log of stock. Lots of other companies to choose from though. Lots of the crawler places out here sell Richmond gears

http://www.richmondgear.com/index.php/about-us

Linda S

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23 hours ago, warrior maintianer said:

an old trick is to take a bearing and hone the inside so it is a slip fit us it to set up rear and then press on new bearing.

Yes, that is what I would usually do if in my other shop where I have lots of old bearings in a box by my press. No such extra parts here where I am now for the next few months. 

On the subject of Yukon Gear not showing a part # for the "four cylinder" rear.  This kit was purchased from Yukon Gear two years ago when they did show the kit.  I have no idea what has changed since then.

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I've had 2 done for me, both 4.56:1

The first was by the Toyota dealer and was a gear/pinion swap.

The second was a complete 3rd member replacement also done by the same Toyota dealer.

Both went with any issues.

 

This is NOT something I would want to do myself.

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For somebody with mechanical skills - it is not a tremendously difficult job.  Not when the gears are correct for the job.  Main things is - having at least a 12 ton press and a split-bearing holder. The split-bearing holder is needed to grip the pinion-bearing when pressing it off. That often has to be done several times.  Unfortunately - with most automotive rears - there is no way to pre-determine proper gear placement and the correct shim-pack thickness.  So it is a "hit or miss" process requiring that that the differential be disassembled and reassembled several times.  Having to do so only 2 time is likely best-case scenario. Having to do it near 30 times is just plain annoying.

Now with big equipment - e.g. John Deere log skidders and farm tractors - it's different.  Gears and carrier are factory stamped with measurements/numbers.  So all it takes it decoding the numbers and the proper shim pack can be calculated the first time. No so with a Toyota 8" rear (and likely the same with the others).

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Anyone who can assemble and disassemble a differential 30 times and call it "just plain annoying" is a real sportsman in my book. I'm not quite sure what my response would be, but likely unprintable. That said, I'm really glad you put together the info for us, cause I've got some gear-work looming in my future.

Thanks,

TG

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Love reading this stuff, thanks for all the detail and great photos. Wish I had time to learn (and do!) more of this kind of work.

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