BJ8 selector shafts and forks condition

[AUSMHLY]

Having the BJ8 transmission (with OD) rebuilt.

Having issues with 2nd gear. Mechanic replaced laygear with new on from AHSpares (had to sand both the front/rear Thrustwashers to get the Laygear in), replaced 2nd gear with an excellent condition use one, 2,3,4 Denis Welch baulk rings, new 1st motion shaft bearing and main shaft bearing.

How can I tell if I need to replace the reverse, 1/2 and 3/4 selector shafts and forks?

I watched the mechanic insert the selector shafts in the forks. Reversed slid in, 1/2 and 3/4 he had to hit with a brass hammer multiple times, with force, to get them to pass through the forks. (Should they slide in without help from a hammer?) Mechanic pointed out that the 3 shifting forks were in good condition. Last time tranny was worked on was 30,000 miles ago. Shifting shafts and forks were not replaced.

Trannys in car, test drive I found shifting was tight between all gears, all gears sound louder then before rebuild. 2nd gear is loudest and gets louder when decelerating. Sometimes at a stop, I couldn’t get into 1 or 2nd and had to start in 3rd.

Drained the oil to find metal filing on the tranny magnet I'm using. No metal filing on the OD magnet. Some gold colored filing on the bottom too. (Maybe the shifting forks or the Thrustwashers?)
I need to find out why the tranny is not shifting as smooth and easy as other BJ8's I've driven. Why the noise and the metal filings.


Tranny out of car, back to the mechanic. With the top off (no oil in the tranny) he could slide the reverse fork with his hand, 1/2, 3/4 he could not. 1/2 fork he needed to tap it with a rod and hammer. 3/4 he had to tap it a lot harder. He needed to use the hammer to get 1/2, 3/4 out of gear. With the top on, it shifted in all gears, but not easily.

Could any of this be because of the selector rods or forks?

 

[Bob_Spidell]

That's a lot of questions (would help if they were enumerated). Anyway, some thoughts:

You obviously have a ferrous part wearing badly. Hard to say without seeing the guts of your gearbox but your shift rods are hardened steel and wear like this from them is highly unlikely. The thrust washers are likely made of bronze--softer than brass and somewhat darker/oranger in color--the shake in your pan is probably brass from one or more shifting forks. The only ferrous I can think of off the top-of-my-head is the gears, one of the fork setpins or the case itself. Unfortunately, the new laygear may be the culprit (or it's caused other parts to wear).

Having to pound the shift rods into their forks sounds unhealthy. They're snug, but not interference, fits. It's been a few years since I last overhauled my gearbox but, IIRC, I tapped them in with a plastic hammer. You could conceivably crack a fork with too much force. One of my shift rods was slightly bent; I straightened it in a vise and it's given me no problems.

As for the forks, when to replace is subjective. The parts that engage the sliding hub wear, as designed. IIRC, I bought new 1/2 and 3/4 forks from DWM, but punted on the reverse fork. I think I kept the old ones; I'll see if I can dig them up tomorrow and take some pictures. I think the only tell is it takes excessive movement before the fork engages the hub but, again, it's subjective. Looking back, I think I could have gotten away with putting the old ones back in, as I won't be driving my car as much as I once did and they'll likely outlast me. The reverse and 3/4 forks can be restored by a good machinist by brazing up the 'pads' and milling them back down to 'spec' (I'd done this once before with the 3/4). I measured the 'business end' of the brand new DWM 3/4 end and a used one I'd bought years ago and they were within a couple thou.

On my gearbox, I safety wired the fork setpins as close as possible to aircraft assembly requirements (FAA Doc. 43.13) with stainless wire; I didn't want those buggers coming out:

EDIT: I just recalled that, I think, BJ8 synchros are steel or iron, the ferrous material could have come from them.

 

[Bob_Spidell]

Here's the photos. The 1/2 shift 'collar' is still serviceable. Of the two 3/4 forks the top one is the one I took out, the darker bottom one is a used one I'd bought a long time ago. All are serviceable--the top one had been re-machined once--and the used one is only very slightly worn compared to the new DWM one. My reverse fork was worn, but still serviceable. I wasted money; if I had to do it again I would not have replaced the 1/2 collar, and would have used the used 3/4 fork I'd acquired, but I didn't want to have to do this job again.