LSD Solution

General discussion about our beloved Tercel 4WD cars
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Petros
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Joined: Sun Jan 28, 2007 6:31 pm
My tercel:: '84 Tercel4wd w/extensive mods
Location: Arlington WA USA

Re: LSD Solution

Post by Petros »

LowBuckCanuck wrote: Fri Nov 10, 2017 11:09 am The way diffs work has always seemed like gearing wizardry...

I would be interested in putting this in the rear so I can use the 4wd on the street if need be.
the reason you can not use 4wd in the Tercel4wd on the street is it has no center diff, like the AWD cars. putting in an LSD does not change that.

It is not so much a mystry how the open diff works, there are some good youtube videos giving graphic images that might help, but what the spider gears in the middle do is allow the left and right wheel to drive at different speeds, which is what happens when you drive in a turn (each wheel traces a different radius turn, one longer than the other). The differential allows the wheels to have "differential" speeds. an unfortunately undesirable affect, if the wheels have different amounts of traction, is if one wheel slipps, it allows all the driving froce to go to that wheel. of course if both wheels have good traction, there would be no slipping.

what a limited slip diff does, it has clutches on each axle (within the diff), that if one wheel slipps, slows or stops it from spinning. Often you get a quarter turn of slip out of the wheel before the clutches engage, hence the term "limited slip" differantial (or LSD). for big powerful off road vehicles, they need large multi-plate clutches to handle the power through the axles. On our cars, that is not so much the issue, since we do not have that much power to start with.

What this adapter does is rubs against the side of the spider gears, adding some friction between the left and right axles, and giving you some limited slip action. the surface area of the "clutch" is not very large, so the effect it not likely as strong as a typical multi clutch LSD, but for the money, it seems it should improve traction on loose sloppy roads. Any traction improvement should help you get though icy or wet snowy roads better than not having it.

I have heard that LDS harms fuel economy and has some effect on tire wear, so the idea solution it seems to me is to put the adapter into the rear diff on the Tercel4wd. for normal street driving you are still on the open front diff in FWD, and the rear wheels are just free wheeling. than when in 4wd, on loose surface roads, the extra traction in the rear should make a big difference, particularly on steep up hill runs.

At that price, it is worth giving it a try. the rear diffs sometimes get sloppy because of the compression washers used by the factory. so rebuilding one that has a lot of miles on it, installing new seals, and shims instead of the compression washers, with the LSD adapter would not be an unreasonable thing to do.

Any suggestion on which of the cheap ones is worth getting? I have a project 4age conversion Tercel in my garage, this would be perfect for it, along with the brake and suspention up-grade detailed elsewhere on this forum.
'87 Tercel 4wd SR5 (current engine swap project)
'84 Tercel 4wd (daily driver, with on going mods)
'92 Mazda MPV 4wd (wife's daily driver)
'85 Tercel 4wd DLX auto(daughter's daily driver)
'01 Honda Civic (other daughter's daily driver)
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