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'98 Rav4 2nd new clutch still slipping

About nine months ago the clutch on my '98 Rav4 died. (This was not the original clutch, it had already been fairly recently replaced by the previous owner.) We got it replaced and everything seemed fine - it engaged a little late when I released the clutch pedal, but I figured that must be normal for the Rav. About six months after the repair it started slipping very, very occasionally and only when I was accelerating (or trying to) in 4th or 5th gear. It seemed worse in cold weather, but since I was living in south Texas at the time, cold weather was pretty rare even in October. I took it back to the mechanic a couple times and he couldn’t replicate the problem which seemed reasonable since I could go weeks without it slipping too. Then I moved to northern Wisconsin and the farther north I got the more reliably it slipped in 4th or 5th, though still only when I accelerated. I took it to a mechanic up north and he said the clutch was bad, which was a shock since it was only nine months old at that point. So I contacted the shop down south and autozone where the part had come from and eventually arranged for autozone to give me a new clutch and cover the labor for replacing it since the whole thing was well under warranty. The mechanic up north put in the new clutch, test drove it, and voila, car still slips in 4th and 5th when you accelerate. So the northern mechanic’s theory is that the mechanic in south Texas who did the first repair resurfaced the fly wheel and either didn’t shim it or shimmed it and the shims died. (Autozone apparently doesn’t sell fly wheels with the 98 rav4 clutch, so the fly wheel hasn’t been replaced.) I’d ask the south Texas mechanic, but they never made a record of this repair (or as near as I can tell, any repair) other than a very basic ‘replaced clutch’ note in their ledger - so they have no idea what they did or didn’t do. So now I’m facing another charge for 11.5 hours of labor to take the clutch out, replace the fly wheel, and put the clutch back in. My question is - is this likely to take care of the problem? Is what the mechanic is describing likely to happen? If it really is a fly wheel issue, why did it take so long for the problem to show up the first time and now even with a new clutch the problem is just as bad as it was before? I can’t afford a new car but this third shot at fixing my clutch in nine months is bringing the bill awfully close to what the car’s worth.

Your first mechanic sent off the flywheel to a machine shop that machined it improperly - no doubt. Flywheels are not “shimmed” per se, but some are machined with a “step” and if a machine shop is careless, they’ll machine out the step - bring it flat and true, and your clutch will slip. I’ve seen this happen before, and you can see the look on the machinist’s face when he says “what step??”. Unfortunately, you’ll probably need to replace your clutch assembly again - once it’s slipped at all, its toast. Good luck - sounds like your “North” mechanic knows what he’s doing, so this should fix it.

Stepped flywheels require machining the mounting pads to allow for the newly machined depth of the friction surface. Few automotive parts stores are able to properly machine such flywheels and a well equipped machine shop is needed and the specified depth of the offset is necessary. Question the new shop regarding now familiar they are with such a clutch/flywheel.