11 replies to this topic

[Spherix]

Hi there,

 

I was going over some last details before installing an otherwise perfectly fine 1275, when I figured I hadn't checked the diff shimming so took the diff out.

 

I then noticed a crack in the diff casing itself, as the picture clearly demonstrates. I haven't ran this engine myself, and other than this crack everything else (including the bearings) look to be in perfectly normal shape.

 

Seeing as the bearings are not supposed to turn in place on that surface, would it hurt either just installing it as is, removing the chip and installing it, or should I source a new housing? I've read on the forums that the casing and the cover are a matched set, hence I'd be interested in avoiding a full gearbox rebuild at this point.

 

Perhaps an even more important question; how would damage like this occur in the first place?

 

[KTS]

i'd start by removing the chip and checking the crack hasn't propagated further into the housing beneath it

 

from the marks in the tunnel it looks like the chip doesn't extend much, if at all, under where the bearing outer race would locate, so i'd think it would be ok. might be worth having the tunnel checked for roundness as a matter of course though

 

as for possible causes;  maybe someone dropped something on it, or maybe there was some detritus under the edge bearing when it was installed last, causing the edge to burst when it was tightened down.

[sonscar]

looks to my inexperienced eye that the bearings have spun in the housing already.Loctite?Could be that the chip was raised slightly and prevented proper fit previously.Good dose of looking at needed,Steve..

[Spherix]

Thanks for the suggestions, ill gently mark the end that hasnt broken through yet with a small saw so that when I tap it off it doesn't form a bigger crack than it is now.

The bearings do seem to have spun on both sides, there are similar marks on the gearbox case although I can't feel them with my fingernails.

@sonscar are you suggesting to put loctite on the outer bearing surface to keep them in place!? Bearings should take the path of least resistance, I'd have figured someone either wouldnt have put the case together well, or the bearing itself was shot.

I would almost dare say this one hadn't been opened since thw factory as when I undid the bolts that have the lockstrip on them, a vacuum released with a bit of a funky smell to it hehe.

[Spider]

I'd just pick that out and satisfy myself that it won't leak from there, then fit it.

 

In regards to what may appear to have spun, it may have been assembled at some point with gaskets when it maybe a gasketless casing.

However, the witness marks in yours look normal to me and not from spun bearings.

[Spherix]

That picture may not have shown it clearly, but I'd still guess they have spun if you see the rest of the casing.

 

 

The engine came with an abandoned project I bought, one diff cover was off without any bolts so I had purchased new ones from Minispares and had it covered up until I had the time to inspect things, which is now.

 

I hadn't done up the bolts very tight for obvious reasons, but it seems quite obvious why the chip came to be now that I've removed it. The tiny nugget on image #2 almost looks like the end of an old bolt that has been drilled out/snapped off, hence putting a new bolt in would've pushed that through...?

 

 

 

I do have a potential leak point now. I guess I'll simply put some loctite on that bolt to prevent any oil passing through...

[steeley]

Looks like somebody in the past may have put a bolt that was too long in that hole and pushed the back out

I would see if you could get it welded up

[Spherix]

Hmm, after inspection of the bolts I noticed a bit of an oddity.

 

1. None of the bolts have spring washers fitted

2. R/H side that came with bolts in place, has 2 bolts 5/16 1" long, and 3 bolts .2" shorter (.10 long instead of .12? inches are a never ending mistery to me).

3. L/H side that came without bolts, I bought 5 new 5/16" 1 long bolts as per Minispares website. They came with blue loctite on them, and I had fitted them without a spring washer.

 

Dry fitting these in the side covers shows I have probably forced this crack myself, as they won't turn in all the way nicely. The shorter bolts from the other side go in all the way in the 'broken spot' without a hitch or spring washer fitted. 

 

Should I be adding spring washers to all bolts, and use 2 1" bolts and 3 shorter bolts on the left side, as was fitted on the right? Seeing as Minispares doesn't list any differences I blindly followed them.

[steeley]

I believe that there are two longer bolts for the holes where the bottom exhaust bracket goes

The bracket only goes on one side and these two bolts are slightly longer than the rest of the bolts to allow for
the thickness of the bracket ( why they couldn’t all be the same I don’t know)

There shouldn’t be spring washers on any of the bolts, they are just loctited in

The reason I know this is when I changed my final drive I put all the bolts in the right holes but
Forgot to put on the exhaust bracket, when I torqued them up, bingo I bottomed out the bolt and stripped the thread

Time for a helicoil

[Spherix]

Visited the local British specialist to get some parts and clarity: the washers were only used with the non-flanged bolts until the 70's what they could recall, the longer ones were indeed used on the exhaust flange. They order most of their parts via Moss Europe, and those also have the spring washer in the diagram, bit of an oddity.

 

I've picked up shorter bolts and a diff housing with the same casting number, if it's a good match I'll just use that one instead of risking a leak.

 

Long story short, check bolt lengths vs hole depth in aluminum before tightening Thanks everyone!

[Spider]

The witness marks you are seeing from the diff bearings, while giving the appearance of having spun, are normal. Every gearbox I've pulled down looks like that. Had they spun, there'd be a step in the cap (as that's the loaded side).

 

I use 5/16" x 1" bolts on the side covers, however, I do fit them up with a medium - heavy grade Spring Washer and a Flat Washer (yes, I know !). If you were to omit the Spring Washer, as I recall, you ideally would want bolts of 7/8" length, which are odd ball. I recall trying 3/4" but felt they were just too short to be comfortable with.

[Spherix]

It took the garage I went to a while to find that length in their bin of spares as well! I'll fit some washers to be on the safe side as well. You're right on the witness marks, a second or two rub with some scotchbrite and they were as good as gone.

I had fitted the alternative cover for a second, but its a poor fit in comparison to broken one, about a gasket width of thickness as a gap between the gearbox case and the cover. I reckon that's a risk in terms of leakage. Put the old one back on and its a perfect snug fit. Decided I'd go with the broken one, put the side cover and the bolt in, applied some oil proof sealant on the inside and I'll let that dry before installing. Easier to plug a small hole vs the entire casing surface.