Re: Installing a R11 overdrive in my 1948.

Posted by HH56 On 2011/5/18 16:37:06

The reverse safety lock out switch was a retrofit added to R9 cars in 47 and was available or could be installed on earlier as well. Even with the reverse lockout plunger which they all had, if a bad switch or electrical short kept the solenoid engaged on the R9, because of the mechanical construction, going into reverse and applying power would lock and could damage the OD. The safety switch forcibly cut the power to the entire unit via the gearshift linkage so the solenoid had to drop out. R11 was a different mechanical design so no longer had the problem. The other regular lockout switch just keeps the OD from engaging in normal operation. On the R9 it was in the ground circuit to relay, R11 is in the power side.