Black powder in B4.1 Tranny
 

I've just stripped my B4.1 transmission after loose diff issues, then gritty/notchy diff after tightening whilst racing on sunday, and the tranny was full of really smelly black powder.
It's been about 4 race meetings since I stripped it previously, and it was the same then as well, the first rebuild from new.

I'm just interested to know if this is typical, and where the fine black powder is from?

I thoroughly cleaned it with toothbrush, tissue and motor spray. There was no wear to the transmission casings. There is some tooth wear to the idler gear and diff gear, but the topshaft looks fine. The smaller bearings were all fine, but one of the larger outdrive bearings was very gritty (to be replaced). The diff was packed with more of this black powder. No wear to the ball seats in the centre gear. The diff plates were worn from the balls.

When I built it, it went together all very clean, and with just a tiny drop of silicone grease on the gears which is worked in.
I've ordered a new idler gear, and have the diff gear as a spare already.
I'm going to rebuild with as many new parts as I have, and will replace all bearings with new spares, and recycle the small bearings as front wheel bearings, as they spin fine.

Is the black powder from internal gear wear? or is it dirt passing through the outdrive bearings into the tranny? or is is slipper dust that has passed into the tranny through the top shaft bearing/ tranny case?
Any ideas?

I guess no one has stripped down their B4.1 transmission before?

It's now rebuilt with new components (plastic gears, all new bearings, etc). Lets see how long it takes to get full of the black stuff again now. It was only four race meetings after last rebuild.

The car is 3 months old, and I do keep it clean after every race meeting.

That's very odd. Is it possible that the grease you are using is drying up in the gearbox ?. Is the transmission free spinning when built ?. Others on here may disagree but I doubt much dust would get in gearbox from racing if if it did I would expect it to take a while. For me it's either a gear binding on the Gbox, binding on each other or the grease.

The transmission rotated really freely. Spinning the wheels, it ran on for ages (with no pinion).

I'd just applied a very small amount of silicon grease to the layshaft gear and idler gear, which was worked in. Only a tiny amount, it almost disappeared when worked in rotating the box before assembly. It wasn't packed with grease, and there was no grease binding the tranny.
I've left it totally dry this time i've rebuilt.

There was some wear to the idler gear teeth, and less wear to the diff gear teeth. I'm guessing the idler gear wears more as its in contact with the metal layshaft gear.

The four small bearings were all free of dirt internally and span freely. One outdrive bearing was free, the other was rough and didn't spin freely.

It ran for four meetings, two on carpet, two outdoors/grass/astro.


I've now rebuilt it, replacing the diff and idler gears, and all bearings as I had spares.

I do wonder if dirt passes into the transmission either through the bottom square in the casing that's exposed in the rear arm mount/chassis plate, or passing either through the outdrive bearings, or through the bearing seats of the outdrives. Another thought is through slipper dust through the bearing seat of the top layshaft. I wonder if a shim kit would take out any slop, or that small side to side movement of the diff and layshaft, preventing any dirt pass through? it's just a theory, but i'm puzzled as to where else it come from.

It is strange. I ran a b4 for years and I still run a x6 which I believe has the same gears in as I b4.1 with no problems at all. Is the layshaft free from play ?

X6 has an extra idler gear in, but essentially the same.

I just checked the layshaft, now its built up. no side-to-side play with the slipper and spur on. When stripping and building it up, there was some slight movement without the slipper on. There is a wear mark, but not a ridge on the layshaft where it fits in the outside bearing.

I've just broken in my diff and checked it's adjustment. its silky smooth. Removing pinion, the tranny rotates really freely with a spin of the wheels.
I'll run it like this and inspect it again after my next outdoor meeting.

it sounds to me like the grease you are putting in is drying out and turning to powder, i know you said you only put a small amount in it might be worth putting more i probably put to much in mine but also never had this problem even with my old b4.1 after a whole season racing. thats not to say it had dried a bit

But there was only the smallest blob of AE clear silicone grease, literally less than 2mm^2. Nothing near the quantity of black powder inside. The powder was black, almost carbonised.
I could understand that if i'd packed it with grease, like a black moly grease, but I didn't.

The idlegear was most worn, only slightly on the faces of the teeth, but again that's light nylon or whatever its made of, not black. There was no component or plastic wear to the casings or anything inside, other than the idler.

I've rebuilt it totally dry, with new gears.

If you are running dry (or almost) it could be plastic scraped off the load faces on the gears.
Yes its white/yellow/cream coloured on the tooth, but once you've heated it up and scraped it off, it could well be black/grey/manky......

(i ran my B4.1 with grease on ALL the gears, its still going strong now.)

I thought it could be tooth wear of idler and diff gears, and to some lesser extent the metal layshaft gear, but there was far more powder than wear to the teeth.

How much and what type of grease did you use? how was the gear wear when you next stripped it down?

So what's the general consensus on lubing the gears in the transmission, and what's the best lube to use? black moly grease? silicone grease? lithium grease? some oil? or running dry, like the manual indicates?

It wouldn't surprise me if they said to run it dry, and if it causes excessive wear. it sells parts...

I got this problem too!
Black power and quite a bitt actually...

Also the idler gear is worn at the top of the teeth.
I also notice that there are some chips of it,
some little dark spots like the top metal layer is removed.. (just some small spots) maybe this causes the idler to wear quicker.

Also the bigger gear seems to be worn a bit I now have my B4.1 for 1,5year I guess maybe it's time to replace the gear?

I just wanted to start a thread actually because I'm looking to but a X factory Top shaft, I'l heard somewhere that it quality is much better.
So my question is does it fit the B4.1?

I run the silicone grease, also I'v heard that some people run silicon oil in there diff. I think around 50wt and just a few drops.. Could this help?

X factory use the associated gears.

Great so they will fit I'm going to buy thel rightnow!

Neal do you also have that 'scratching' noise at a certain rpm?

The transmission was noisier, like when running a worn, non round kit spur.
do you mean screeching whine of the gears, or diff slipping bark?

Yes I replace the stock spur with a RW Racing one

The gears not the diff
When I hold the car off the ground and apply 1/4 throttle there is a scratching noise if I go higher in rpm then there less noise..

Btw,

here is a picture of the problem I got with the topshaft:
http://http://www.novexa.com/images/...d/pitting1.jpg

It's called 'pitting' I saw this at school :p

Ok. my topshaft wasn't worn like that, only the plastic idler had tooth wear.

Just some lithium grease i had lying around. I only sripped it down 3 times in the time i had it, but the gears (while slightly discoloured from the blue grease) were untouched.

And you can get a lot of powder before you start to see the damage to the tooth flanks.

were they new or secondhand cars?? some people put grease on their gears, i have also used graphite dry powder lubricant in gearboxes in small quantities, could it be something like that??

Mine is new, 3 months old, run once or sometimes twice a week. Rebuilt transmission twice now, the first time was a stripdown to service an over tightened diff, after a rear wheel bearing collapse. the second time, this week, after running four race meetings since the last rebuild.

I'll photograph the wear to the idler.