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MGB 66 mgb trans noise

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I have a '66mgb undergoing restoration. The car only has 48k miles on it and the trans grinds badly going into second gear. The trans is out an inspection plate is off. It was filled with gear oil when I bought the car and pulled the trans. Not sure if that can cause the bad grinding noise. It appears the trans has been apart before because of the gasket sealer around all the covers. The gears look to be in good shape as do the synchro's. Very little to no wear on the triangles on the synchro's...any thoughts or suggestions before I tear it down. Thanks,Chris
 
One thing: you said "gear oil". It should be full of Castrol 20W50 (same oil that's used in engine)

If someone filled it with gear oil, there's a pretty good chance they were trying to hide a problem. If there's gasket sealer around the covers, it has been apart before.

Were I restoring the car, I'd pull the transmission apart, clean everything, check for problems, repair as necessary & rebuild.

I have a question: how did you verify the mileage?
 
I think I will pull it apart anyway. There is some wear on the 1-2 syncro. Maybe a couple thousandths of an inch on the engagement side. The gears all appear to be in good shape though. I figured the orginal owner thought the gear oil would help and I was aware it should have been filled with 20/50. Mileage is actual. I knew the previous owner who had known the guy he purchased it from. Also actual on the title as well. Been sittin around for years. Unfortunately outside for quite a few of them.
How much wear is allowable for the syncro before it has trouble? What else would cause it to grind going into 2nd? In my opinion, being around cars all my life, it doesn't look like the syncro is worn enough to cause the grinding. Is there an adjustment that can be done? Thanks again, Chris.
 
The "grinding" noise could well be the layshaft and/or input/output bearings. Nothing short of a complete tear-down & inspection would tell. That's a three syncro box and could have a bogus ('white-box') second gear baulk ring in it, too, if it shows evidence of having been apart before.

They do tend to "zizzle" a bit even when all is right.
 
Doc's correct, they do "zizzle" but MGB transmissions rarely break unles they were driven hard - & I mean real hard, as in beaten up or raced.
 
...or repeatedly shifted into first or reverse while rolling...
 
My point exactly.....no MGB with 48,000 original miles should have anything wrong with the transmission....they're almost bulletproof!
 
Thanks guys. I don't know how the car was driven in the past. It was definitely neglected. I am going to tear the trans down over the weekend, but visually, I don't see anything obvious. Time will tell once it's torn down. The trans was quiet as can be while driving, but it would grind pretty good going into second, either from first or third into second.
 
Then it's just th' baulk ring. Likely it or the second gear (not as likely) are kaput. A scinter'd iron synchro is in order and you're good to go! :thumbsup:
 
Can I use the steel syncro? The one's in there are brass in color. If I go to a steel syncro I have to also change the second gear. correct?
 
DrEntropy said:
...or repeatedly shifted into first or reverse while rolling...
Click to expand...

What's wrong with that? I thought that was how you got the gears to be synchro in the first place, once all those sharp teeth are gone it'll slide into 1st with no problem.
 
Oh yeah. With a REALLY noticeable "KLUNK" on th' last time. :smirk:
 
So, does this mean that I can use a steel syncro or not??
 
The second gear one I recall as "proper" is made of sintered iron, not steel per-se. The gear need not be replaced unless the cone the serrations (ring I.D.) contact protrudes beyond the bore of the ring edge when offered up. The other two rings are bronze in colour. Unless their points are worn, they're usually considered serviceable/usable.
 
Using the workshop manual, I can NOT get the rear extension off this trans. Anyone have any thoughts. Don't hesitate to give me a call. This was my project for the day...it looks the gears are holding it in..thanks, Chris 330-204-4199
 
You have the speedo shaft/gear out, yes?
 
Yep. It looks like the second speed gear is making contact with the larger middle gear on the layshaft. Do I need to pull that large pin behind the front cover to drop the layshaft out of the way?
 
Shouldn't need to, the case extension should come away with the box innards intact.

I'm diggin' fer th' manual now. Stand by.
 
O.K. The larger portion of the second speed gear definitely will not clear the larger middle gear on the layshaft without dropping the layshaft down. Still looking at it.
 
I'm confused now... are you past getting the outer rear housing off the box? If that's the case and you're trying to remove the shaft assembly, the layshaft needs to be "dropped", yes.
 
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