I've had both done once (at 70k miles) and the front re-done (at ~125k miles) on my 190. Now at 150k miles and *just* starting to get the clunk on the downshift - I suspect the rear. Each one is ~$100 for the part (basically a big rubber bushing with some metal inserts for bolts). Have a shop do it though - you have to lower the tranny to get at the front one and I think you need special tools for the driveshaft to get at the rear. My recollection was $450 to have both done (labor intensive) and $300 for for the front only. While in there have them check your tranny mounts - this would be a good time to replace them as well and they seem to wear out between 70-90k miles.

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Makakio
1992 190 2.6
lotsa miles