I am trying to identify the Hurth Transmission in our 1983 Mango and need some help. The data tag is damaged. The only manual we have is in French and is for a HBW5,10, or 20 The manual drawings do not seem to match up with what we have mated to our Perkins 4-236. Our transmission has the shifting arm on the top, not the side as shown in drawings. Our buyers survey refers to it as a Hurth 4 transmission. The transmissiion shifts fine but makes a fair"clunk" while doing so. Is this normal for these small and simple transmissions? Any help would be appreciated. SV Eshamy Michael P. McCarthy