Transmission trouble

fiatfan · Sep 3, 2023

Finally managed to take a short test ride the other day after years of building, unfortunately this ended up.... well not so good. The main issue was a very unpleasant noise somewhere in the transmission, I couldn´t hear exactly where it came from, but I both felt and heard it. It sounded as if a bearing was totally run down, really bad grinding sound. But only when under load, when I let the throttle off a little and just rolled, still in gear, it was quiet. I only drove maybe 3-400 meters (1/4 mile) didn´t want to risk a real brake down. I can say that everything in the primary is new, I have taken all that apart and found nothing wrong. Inside the gear box all bearings and bushes are new, all gears and the axles look fine. The gear box is now empty, all parts cleaned and inspected, and I find nothing wrong...... This is very annoying. When the primary was off and I removed the front sprocket I turned the main shaft and there was a strange rattling sound, just like something was not quite gripping as it should. I can also add that the gear box is of no specific year, I don´t know for sure about the parts inside but the casing has a number starting with "134", so maybe 1969/70? I bought that on Ebay from the USA and it´s in very good condition.
A final question; can you put something in the wrong way around when putting the box together, or do some other weird thing? It would be typical me.... Greatful for any ideas/help.
\Tommy

BERT · Sep 3, 2023

fiatfan said:
Finally managed to take a short test ride the other day after years of building, unfortunately this ended up.... well not so good. The main issue was a very unpleasant noise somewhere in the transmission, I couldn´t hear exactly where it came from, but I both felt and heard it. It sounded as if a bearing was totally run down, really bad grinding sound. But only when under load, when I let the throttle off a little and just rolled, still in gear, it was quiet. I only drove maybe 3-400 meters (1/4 mile) didn´t want to risk a real brake down. I can say that everything in the primary is new, I have taken all that apart and found nothing wrong. Inside the gear box all bearings and bushes are new, all gears and the axles look fine. The gear box is now empty, all parts cleaned and inspected, and I find nothing wrong...... This is very annoying. When the primary was off and I removed the front sprocket I turned the main shaft and there was a strange rattling sound, just like something was not quite gripping as it should. I can also add that the gear box is of no specific year, I don´t know for sure about the parts inside but the casing has a number starting with "134", so maybe 1969/70? I bought that on Ebay from the USA and it´s in very good condition.
A final question; can you put something in the wrong way around when putting the box together, or do some other weird thing? It would be typical me.... Greatful for any ideas/help.
\Tommy

This DVD is an excellent resource.

concours · Sep 3, 2023

fiatfan said:
Finally managed to take a short test ride the other day after years of building, unfortunately this ended up.... well not so good. The main issue was a very unpleasant noise somewhere in the transmission, I couldn´t hear exactly where it came from, but I both felt and heard it. It sounded as if a bearing was totally run down, really bad grinding sound. But only when under load, when I let the throttle off a little and just rolled, still in gear, it was quiet. I only drove maybe 3-400 meters (1/4 mile) didn´t want to risk a real brake down. I can say that everything in the primary is new, I have taken all that apart and found nothing wrong. Inside the gear box all bearings and bushes are new, all gears and the axles look fine. The gear box is now empty, all parts cleaned and inspected, and I find nothing wrong...... This is very annoying. When the primary was off and I removed the front sprocket I turned the main shaft and there was a strange rattling sound, just like something was not quite gripping as it should. I can also add that the gear box is of no specific year, I don´t know for sure about the parts inside but the casing has a number starting with "134", so maybe 1969/70? I bought that on Ebay from the USA and it´s in very good condition.
A final question; can you put something in the wrong way around when putting the box together, or do some other weird thing? It would be typical me.... Greatful for any ideas/help.
\Tommy

ENGINE speed noise?
Or VEHICLE speed relative?

CanukNortonNut · Sep 3, 2023

Check the layshaft 4th gear:

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The embossment should face the layshaft bearing.

Big Phil · Sep 3, 2023

fiatfan said:
Finally managed to take a short test ride the other day after years of building, unfortunately this ended up.... well not so good. The main issue was a very unpleasant noise somewhere in the transmission, I couldn´t hear exactly where it came from, but I both felt and heard it. It sounded as if a bearing was totally run down, really bad grinding sound. But only when under load, when I let the throttle off a little and just rolled, still in gear, it was quiet. I only drove maybe 3-400 meters (1/4 mile) didn´t want to risk a real brake down. I can say that everything in the primary is new, I have taken all that apart and found nothing wrong. Inside the gear box all bearings and bushes are new, all gears and the axles look fine. The gear box is now empty, all parts cleaned and inspected, and I find nothing wrong...... This is very annoying. When the primary was off and I removed the front sprocket I turned the main shaft and there was a strange rattling sound, just like something was not quite gripping as it should. I can also add that the gear box is of no specific year, I don´t know for sure about the parts inside but the casing has a number starting with "134", so maybe 1969/70? I bought that on Ebay from the USA and it´s in very good condition.
A final question; can you put something in the wrong way around when putting the box together, or do some other weird thing? It would be typical me.... Greatful for any ideas/help.
\Tommy

This looks like a useful article that might help:

Old Britts, Assembling the Commando gearbox

fiatfan · Sep 4, 2023

concours said:
ENGINE speed noise?
Or VEHICLE speed relative?

Not related to engine revs, not specific for any gear, same noise on first and second gear.

Schwany · Sep 4, 2023

It is possible to install the mainshaft 1st gear backwards, but I'm not sure the inner cover with bearing will go on in that scenario. I've never done it. However, I have started putting the mainshaft 1st gear on backwards and caught myself in the process. Longer flange is outbound.

You don't have to buy the DVD. There is a Mick Hemmings PDF version gearbox overhaul document with some pics and text out there somewhere. Might even be on this site. Try a search on "AMC gearbox overhaul" here and then on google. It does assume some familiarity with the gearbox.

concours · Sep 4, 2023

fiatfan said:
Not related to engine revs, not specific for any gear, same noise on first and second gear.

Please don't be offended, but chain/guard can make some ugly noise. It's worth a visual inspection.

concours · Sep 4, 2023

fiatfan said:
Finally managed to take a short test ride the other day after years of building, unfortunately this ended up.... well not so good. The main issue was a very unpleasant noise somewhere in the transmission, I couldn´t hear exactly where it came from, but I both felt and heard it. It sounded as if a bearing was totally run down, really bad grinding sound. But only when under load, when I let the throttle off a little and just rolled, still in gear, it was quiet. I only drove maybe 3-400 meters (1/4 mile) didn´t want to risk a real brake down. I can say that everything in the primary is new, I have taken all that apart and found nothing wrong. Inside the gear box all bearings and bushes are new, all gears and the axles look fine. The gear box is now empty, all parts cleaned and inspected, and I find nothing wrong...... This is very annoying. When the primary was off and I removed the front sprocket I turned the main shaft and there was a strange rattling sound, just like something was not quite gripping as it should. I can also add that the gear box is of no specific year, I don´t know for sure about the parts inside but the casing has a number starting with "134", so maybe 1969/70? I bought that on Ebay from the USA and it´s in very good condition.
A final question; can you put something in the wrong way around when putting the box together, or do some other weird thing? It would be typical me.... Greatful for any ideas/help.
\Tommy

Check the shift forks/rod not bent.
Check the shafts are good.
Check the sleeve gear bearing isn't a problem as well.

Some Andover Norton transmission parts quality escapes (2015)

I had the opportunity to repair my failed transmission (still working, but 2nd had a funny "thump, thump, thump" noise. Disassembly revealed a LOT of damage.... I set to work inspecting (the case, sleeve gear and first gear lay were the only usable moving parts) and ordering parts. When I...

www.accessnorton.com

Matt Spencer · Sep 4, 2023

" ... This is very annoying. When the primary was off and I removed the front sprocket I turned the main shaft and there was a strange rattling sound, just like something was not quite gripping as it should. "

You mean you turned the gearbox mainshaft ( rather than the crankshaft ?

It actually sounds like its in the clutch / primary or rear sprocket / chain . perhaps .

Its still a triplex chain ?? Adjustment reasonably correct is essential . AND the fit of the securing bolts . Typical grossly negelected / abused is a elongated bottom hole , WHICH ,
if the gearbox were skewed - youd get CHAIN RUBBING .

But as you say 1st & second . Is it ONLY in 1st & 2nd gear . ? ? ? . also alternator ' fit ' is important - miss placed things there arnt healthy , graunch crunch & bang wise .

Any litte bits of metal powder ANYWHERE ? ? ? .

fiatfan · Sep 5, 2023

Matt Spencer said:
" ... This is very annoying. When the primary was off and I removed the front sprocket I turned the main shaft and there was a strange rattling sound, just like something was not quite gripping as it should. "

You mean you turned the gearbox mainshaft ( rather than the crankshaft ?

It actually sounds like its in the clutch / primary or rear sprocket / chain . perhaps .

Its still a triplex chain ?? Adjustment reasonably correct is essential . AND the fit of the securing bolts . Typical grossly negelected / abused is a elongated bottom hole , WHICH ,
if the gearbox were skewed - youd get CHAIN RUBBING .

But as you say 1st & second . Is it ONLY in 1st & 2nd gear . ? ? ? . also alternator ' fit ' is important - miss placed things there arnt healthy , graunch crunch & bang wise .

Any litte bits of metal powder ANYWHERE ? ? ? .

Ok, so I turned the gear box main shaft, BUT the worst noise was when I turned it the wrong way (clock wise).... didn´t realize that at once. Was a small rattle when turning the right way, but should it be a loud rattle at all?
About the primary, there is a new RGM belt and dry clutch, inner trans is new, stator is new and adjusted correctly. I only drove it a short bit, heard the noise and turned around, didn´t feel like taking a long trip with that.
There was a small (really small) amount of small metal bits on the magnet in the draining plug, but after I had washed and looked closely on all the inner parts in the box I could not find any damage anywhere.

Transmission trouble

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