I was going to open a new thread and I read this one, 9 years old, which describes exactly the symptoms on my side-shift BT7: third gear grinding when shifting rapidly for a sporty driving. It grinds from 2nd to 3rd, and also down shifting from 4th to 3rd. It does not grind if I select 3rd below somewhere around 2000 rpm, (driving gently).
I purged the clutch circuit to insure there was no air. The car was a rebuilt, including transmission, when I acquired it in 2015. The crunching 3rd gear was already present at the time, and it still does today after 30,000 km. I thought is was an inherent problem in this old design transmission (which it may be according some answers), but I have since acquired a 100/4 BN1 and fitted a 4 speed BN2 transmission, which is basically the same design of the 3000 Mark I, and the 3rd gear does not grind when up shifted or down shifted.
I have discussed the issue with some specialists in my area (France) and I hear some having fitted steel baulk rings on the side-shift box - to replace the original brass rings - with good results.
I wrote to Denis Welch hoping for confirmation of this, but the answer was that the steel rings are for BJ8 only.
I have open the side cover to inspect the rings, and for as much as I can see, the rings, including 3rd gear, are not "bottoming" to the gear cone, making me think it is not worn out.
I plan to remove the transmission from the car and take it apart for closer inspection of the rings, especially 3rd gear ring.
My question is: are the steel baulk rings a different profile compared to brass rings? This would be a reason for impossible swap.
Are the gear cones of the BJ8 manufactured with a different surface treatment, to withstand the steel baulk ring friction? This would, over time, ruin the surface of the gear cone.
I plan to order a steel baulk ring and mate it to my 3rd gear pinion, using engineer's blue to confirm the surface contact. I think a good practice is to lap the ring to the pinion to obtain a perfect match.
Will appreciate any comment to guide me in this process, especially from persons who fit steel baulk rings in a side-shift transmission, if any.
I can verify the proper mating of the gear cone and baulk, but the surface hardness of the gear will remain a question.