21 Turbo 1988 Red R21 Turbo

[Wheelers Workshop]

Having 2 balls and a spring in the Detent hole was probably the non select fault, easy to do if you get distracted at the wrong moment, and will effectively lock it in or out of gear as the spring will be coilbound with the ball in the detent, no chance it is retracting to allow movement.
A warning to all of us, is to physically check you get all the gears on the bench before fitting, The irony would be it could have been checked in the car and repaired in situ. Definitely one to learn from.
HOWEVER. The noise can really only be coming from the 5th gear pair, It's quiet in all the other gears, meaning all the bearings and gears are ok, just 5th pair and only when transmitting drive, they are quiet when idling round when the box is in any other gear.
One gear is fixed to the shaft, so that should be OK, for any unwanted movement, the other runs on a needle bearing, so it's possibly worn, but highly unusual. Leaving the gear teeth themselves.
If it's 4 wheels away from a road test, I would try it, mainly to see if it is only noisy on drive, or is it on coast also.
@Andyquadra joked about it being straight cut, but it covers what is being heard here.
I'm sitting here racking my brains trying to remember if it's possible to fix the fixed gear backwards, I'll need to dig a pair out and see. If it can then it has mixed the coast and drive faces up. It should be noisy on both drive and coast.
That's as far as my thinking takes me.
Paging @Wheelers Workshop Have you got any ideas Dave????

Hi Steve,
I listened to the video clip and 5th gear test running , that does not sound happy at all. As I have to guess why its noisy , then I am thinking 4 things maybe.

1 Mismatched gears?
2 No lubrication?
3 Rotating top gear rubbing ? is there any swarfe?
4 Did I read that a straight cut 5th set have been fitted, they are noisy as you know.
Its inevitable but I can only suggest that the end cover is removed and stripped again to put eyes on the 5th gear end parts and operating fork, bearings etc This is one of those odd issues, and our 353 box 5th detent problems come to mind.
Sorry I have nothing more constructive to suggest.
Cheers
Dave

 

[Renaldo]

I have had a similar noise on a LT77 that had been “rebuilt” -turned out to be a thrust washer missing allowing too much linear movement which was most noticeable when the gear was engaged/had a load acting on it.
This is so frustrating but I guess the only positive is that it should be very obvious what is wrong when investigating due to it being so noisy!

 

[DaveL485]

then I am thinking 4 things maybe.

1 Mismatched gears? - possible.
2 No lubrication? - Definitely not, fresh oil filled just before test.
3 Rotating top gear rubbing ? is there any swarfe? - Unknown without draining it, ill check when I do that.
4 Did I read that a straight cut 5th set have been fitted, they are noisy as you know. - Definitely not got anything straight cut.

>>I am just trying to source a completely different box, to get the car sorted out. I'm £640 plus 12 hours of driving plus the fuel into this now and ive quite frankly had enough.

 

[DaveL485]

Another nasty surprise when I moved the car, found this on the floor.



Along with some gearbox oil. Got under it again.



Give me a goddamn break! Took the housing off, no easy task in the car



the secondary shaft nut has come off the back of the shaft and machined its way through the housing this is ANOTHER mistake by the gearbox guy, thats three errors in 2 rebuilds now. Obviously hadnt been torqued or the soft edge knocked into the flat on the shaft to stop it coming undone. The primary shaft one was done OK, but not this one. No way was it done up with the immediate issues with 5th. It only spent the time in 5th you see in the video.

So. I cleaned up everything, rethreaded the damage on the nut, refitted it and torqued it up to the specified 200nm (!), then bent the locking tab over. Refitted the housing - that took a while until I figured out how the selectors worked and how to align them! But it was refitted and then I left it to let the sealant go off (yesterday). Going to flush some oil through it today and then test it out, if it only gets it out of the garage for a car move around then thats OK. I have another 'box coming shortly with any luck. Gonna have to replace that housing anyway. I covered the hole with a bit of steel plate and some oil resistant sealant for now. Gearboxes aren't pressurised so it'll be fine for the time being.

 

[DaveL485]

Nut refitted



Housing back on, reassembled and all gears selecting (phew)

 

[Steve Swan]

That was bloody lucky... Probably your noise too. Use a little loctite on it. The knock over part is a wind up, it does absolutely nowt. if you manually select a gear and also select 5th you will be able to tighten it up. Remember to put it all back in neutral before re-assembling
You'll know all about these, by the time you're done......

 

[Renaldo]

Wow, that was a nasty surprise and painful to know that nut was acting as a drill bit against the gearbox extension casing!
At least it has pointed you in the direction of the fault/noise!
Fingers crossed the box operates correctly now although you probably have lost confidence in this box.
Hopefully the box you have on its way will be all good

 

[DaveL485]

Still noisy in 5th, although vastly quieter there is still a whine.
Also crunches into 5th if you rush the change.

Sigh. At least I can move the car around now and get Jamie's black one out from behind it.

Picking up another box Friday hopefully. 100% had enough of this one.