Does anyone know where the TRS drive makes the rotation change ? Is it in the upper or lower section. I'm trying to mate one upper to another lower which may be from different sides of the boat. Realy, a quick fix hoping to get back on the water without buying a new drive untill the end of the season. Thanks all.

The lowers are different. Uppers are the same

Mark

There is shimming required when putting an upper and lower together, especially in your case where you are going to use a different lower. Shims are under the bearing race in the upper right there. Refere to Mercruiser TRS manual #5 for the correct procedure.

The original service manual for the tr/trs has imperfections. When changing the lower gearcase to a different lower (irregardless of rotation), the lower must be overshimmed and then backed off to preload specification of 110%, if bearings are new and bearing bores are tight. If installing a used lower with preload of 50% of factory new preload specification, and it feels clean and smooth; then a 75% load of factory new specification should be sought. This is because of the fact that Mercruisers early preload specification was set-up for standard gl-5 90w lubricant and had conservative numbers set because of a cautionary stance of not overloading the bearing bore. Modern synthetic lubricant makes early preload specification entirely obsolete. The overloading of the preload on the lower vertical driveshaft, before removing shims, is needed because of a inherent false positive inevitably obtained simply because of the design of the upper/lower driveshaft bearing, and the configuration of the gearcase......sounds complicated; I know, but in reality it is rather simple. If done in the manner described, it completely eliminates the possibility of "pinion climb" and insures a long performance life.

In the lower, the gears in the lower on a RH run infront of the down shaft and in a LH behind the down shaft !!!

Buying a other used TRS is cheaper then messing with it !

OMG !!!! I'm in WAY over my head here,,,,,you can't just bolt another lower to the upper ? I had NO idea,,,,this is frustrating..........

Just take it into a competent shop that is equipped to work on TRS's. Couldn't take over a hour labor.

Call me; it is not that complicated, and I can easily explain on the telephone 360-738-3100