Monster Beetle gearbox bearings

[Kol__]

Hi guys,

Rebuilt a 1986 MB gearbox on the weekend, full strip down and clean with brake cleaner, added new set of diff gears, new bearings, re-greased with Tamiya's molybdenum grease (good choice?) and also fitted @Xeostar and @Problemchild's gearbox casing brace.

I bought a bearing kit which only consisted of 1150 bearings (BB6 x2 on diagram below). However when going through the gear box, it did already have some old 1050 bearings fitted and some 850 metal spacers around BB9 metal shaft (BB8 x2 on diagram below). My query is, should those 850 metal spacers be replaced with bearings or are they metal spacers for a reason and should be left that way? Cheers

The below is taken from the 1986 MB instruction manual, but as I understand it the diff and all of the gearbox are the same on the 2015 rere except for the pin drive turnbuckle drive shaft setup on the rere.

You can see the bearings and spacers that were already in the gearbox here after the strip down and clean...

[Saito2]

The 850 "metal spacers" are bronze bushings which are a step up from plastic bushings but not a good a ball bearings. IIRC, Tamiya did make 850s in plastic for certain vehicles way back, but their small size meant they wore excessively. At any rate, 850 bushings are mostly bronze bushings in Tamiya vehicles and they can be upgraded to ball bearings if you wish.

Tamiya's molybdenum grease is usually used on metal gearing and ceramic grease is used on plastic gearing. The re-re Hotshot even instructs you to put moly on the inner metal diff gears and ceramic everywhere else. 

[Problemchild]

Most beating kits I’ve had replace the bushings with bearings 

glad the brace is getting used - hopefully you won’t be disappointed 

 

JJ

[Kol__]

Thanks guys.

Exploded view..

The finished gear box looks great with the skid plate and brace...

Should there be any 'left to right' play in the spur gear? At its mount points in the casing, the spur gear sits on a solid rod (BB9) which is capped at each end. Those plastic caps slot into holes in each side of the metal case plates (shown on the top left of the above image). Now it is assembled again, if I press on the caps from the outside, on either side, the spur gear moves slightly left and right within the casing. I have tightened up the brace mounts gradually until the diff no longer moves when pressed from one side or the other, so the tension on the clamping braces seems spot on. I wonder of the play in the spur gear will be taken up when the gearbox is fully mounted back in the chassis?

[Saito2]

Yes, the slop in the spur gear shaft mounts/plastic caps is typical in these. Its probably not too much of an issue as plenty of these vehicles survive years of use. I went overboard addressing many of these issues in a thread on  here titled "Blueprinting a Blackfoot".

[Kol__]

Thanks @Saito2, I was thinking maybe a small washer added to one end of the spur gear shaft could solve the issue, but wouldn't want that to potentially stop the gearbox casing from fully closing as that could cause the diff gears to get mashed and counteract the benefits of the case brace if not careful. I'll check out your Blackfoot thread, cheers

[Problemchild]

Looks fantastic

JJ