Ring and pinion swap

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Jan 19, 2003
I want to change out the ring and pinons in my
'69. I notice that SOR sells ring a pinions for
58-67, 68-72, 72-74, 74-78 etc.

What are the differences in the kits? I would
like to find used 3.70 ring and pinions or 3rd
members to fit with my stock axles (coarse splined,
right?) and driveshaft flanges. I imagine that there
are a lot of gears available from 60 series cruisers
who are going the other way. What should I start
looking for and what should I avoid?

I am willing to set up new rings and pinions; I have
the time and patience and equipment to set up
gears if I need to.
Remember that with the later fine-splined pinion, your driveshaft won't bolt up to the companion flange. And your original companion flange won't fit, since it's coarse-splined. You will need to get a mini-truck flange that is round, and drill it to match the pattern on your driveshaft. ::)
OK. That's cool. What about the axle shafts? Will they
fit into the "new" spider gears or should I use the old
'69 axel shafts are fine spline and will fit later model side gears. I would think long and hard about this as a R&P swap will be the same effect as going from 30 to 33 inch tires and the larger tires are more useful off road. Buying 3.70 differentials would be easier and cheaper than changing the R&Ps.
PinHead, you are right. I will probably end up going to
33's and 3.70's at some point as this cruiser is my
daily driver (in fact, my only car). My off road use
is mostly family camping and on the beach -- not much
call for rock crawling in my life at this point.

What I will probably do is find a proper 4.10 pumpkin
spare (I've seen them for $25) and find a used 3.70 ring
and pinion and go through the process outlined in the
factory manuals. I have all the dial gages, etc.
If I can't get the new R&P dialed in, I will stay with
the 4.10 gears.

I will go up to 9.5 x 33 tires before the 3.70's. I know
that this is exactly the other way that most of you
are heading, but in my case, I need higher gears, not
lower ones.
I might be able to help a bit here. I have run the 33 x 9.5 tires on my FJ-60 with the stock gears(3.70) for several months. It works pretty well and is OK most of the time. On the highway 2500-2700 rpm is a nice cruising speed. Around town, especially from a dead stop the 3.70's arn't that great. You really notice the lack of gearing then. It's also difficult to start at an uphill stoplight. I recently bought 4.11 diffs and have swapped then in over the last several weeks. Even though the gearing difference is only 10%, the gearing feels just right. The stoplight problems are gone, it feels stronger. I wouldn't go back to 3.70's. Ultimately the plan is an H55 5 speed trannsmission, which wouldn't make sense with the 3.70's.
This does help. Since I am running the three-speed
transmission, the combination of 3.70's + 33 inch
tires + the tall first gear might be too much.

What did you do with your 3.70 pumpkins?
Nothing-the're sitting in my garage waiting for a rainy day. I'll probably keep them but if you really need them, maybe we could work something out. I was thinking of getiing one rebuilt with 4.56 to use as a trail spare for my 40.

The swap is a whole lot of oily work, but since I don't know how to set up R&P gears, my only choice was to swap the whole thing. If you know how to do ring and pinion work, I've seen the gears around (Used) for a pretty good price.
Cool. If you ever swap out for 4.56's, then keep
me in mind for the 3.70 R&Ps. I really don't need
them now -- just scheming for the future.
rgentry, I am currently working on installing e-lockers fr/rr in my 60 and will thus have two 3.73 complete diffs just chillun'. I am awaiting a few items and it may be a month or so before it all comes together, but I'd be willing to part with them if you want them then. Send me an email.

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