rattle in 5th and 4th gear

[Killametre]

The pinion flange is the bit that the driveshaft bolts to at the diff, If there is a bearing going you will usually get metal on your drain plug so it might pay to drop the oil and check. If there is a bearing failure it will be cheaper to repair the earlier you get on to it as with most things mechanical.

cheers Andrew

so as a query, is it going to be detrimental to my car running to leave this for a while or should i get in asap and fix it. also, i have no idea what a pinion flange is lol. if someone can point me in the right direction, i should be able to find it. thanks in adviance guys!!!