Technical What is this gear box noise? (Video)

[FIATinCA]

I had a leaky 126 gear box in my 500, so I replaced the nose cone with one that has the updated shift rod seal and I replaced the boots on the gear box end of the axles.

Got it back in the car, and now I hear this noise when rolling it forward or backward:



Any suggestions?

 

[FIATinCA]

You can see it moves up and down a little as it clunks as well

 

[smart51]

It seems to be about 4 times for every 1 revolution of the input shaft. Is it in reverse gear in the video?

 

[fiat500]

Are any of the bolt heads sticking out too far....the ones connecting the sliders to the rubber coupling? Or is a stone or something wedged in that area? It might also be a spline problem. Did you fit the circlips back on the shafts?

 

[FIATinCA]

I’ll have a closer look at the couplers. I did fit the clips and the springs at the end of the axles.

It does it with the car in the air while spinning just one tire also, but it did not do it while I turned the axles on the bench. The axles did come pretty far out of the box a few times, I just pushed them back in and gave them a turn. Seemed fine until back in the car.

Weird. Guess I could pull it back out and see if the axles still turn freely. Stumped!

 

[FIATinCA]

It seems to be about 4 times for every 1 revolution of the input shaft. Is it in reverse gear in the video?

I *think* it's in neutral, but now you have me wondering. I'll take a look!

 

[smart51]

I *think* it's in neutral, but now you have me wondering. I'll take a look!

The input shaft was turning, so it had to be in gear. The noise was about 4 times per revolution of the input shaft. Is there something square connected to the input shaft, or something with 4 bolts?

 

[FIATinCA]

Oops! You're right, of course. I was sliding it in and out of gear, but it's definitely in gear in the video. Hmmmmm. Nothing looks out of place visually, I don't see anything that stands out at the input shaft. I'll get a better look this afternoon and report back. Thanks for looking!

 

[FIATinCA]

Ok, I removed the gear box and threw it back on the bench. I took off the nose cone and turned the axles and the noise stopped.

Put it back on without the gear selector rod in and it was smooth and noise free-- thought maybe it was the speedo drive for a minute.

Looks like I messed up installing the gear selector rod. I just put it back in, tightened it all back up and it seems fine.

Choosing gears is pretty tough, I have to put a screwdriver through the bolt hole on the gear selector to push/pull it. Probably gets easier with the leverage from the stick, I hope.

I've had this car 10 years+, 2nd motor, had both engines in and out a few times, but I haven't messed with the trans til now.

I imagine there's a proper procedure for installing the gear selector rod, does anyone have any info?

 

[Bleeding Knuckles]

Hi, If you go to the 'downloads' section on this site and download the fiat 126 Haynes manual, the gearbox section will tell you step by step the procedure. Good luck.
Ian.

 

[FIATinCA]

Thanks for that, that's a fantastic resource.

"Line up the selector rods and refit the front casing, taking care that the selector lever in the casing engages the slots in the selector rods."

I see how I buggered it up the first time & the little foot end must have been out of place and dragging on something. I'll get it all back in the car soon and see how it goes. That sucker was leaking gear oil like it was being paid to.

 

[FIATinCA]

I finally had some time to get back to it& it seems like it's the distributor drive after all.

I had the box on the bench and every time I tightened down the nosecone, it would start to bind. I'd loosen the bolts and it would turn fine. Weird.

I finally took out the speedo drive unit and reassembled everything, tightened up the nose cone nice and snug-- smooth as silk. I put the drive back in and took it out half a dozen times, same result every time. The drive itself spins freely.

I think it *may* be the new nosecone holding the drive in an ever so slightly different position combined with a worn gear on the drive, and maybe also because I don't have the drive teeth meshing with the same teeth on the gear box shaft as before. Add up all 3 and I'm getting that weird binding.

New speedo drive is probably going to be aftermarket, I assume? Tempted to fab up a block off plate.

Speedo works/worked fine and everything was normal in that department before I took it apart. Two steps forward...

 

[FIATinCA]

Is the speedo drive the same for 500 and 126 gearboxes?

 

[the hobbler]

I finally had some time to get back to it& it seems like it's the distributor drive after all.

I had the box on the bench and every time I tightened down the nosecone, it would start to bind. I'd loosen the bolts and it would turn fine. Weird.

I finally took out the speedo drive unit and reassembled everything, tightened up the nose cone nice and snug-- smooth as silk. I put the drive back in and took it out half a dozen times, same result every time. The drive itself spins freely.

I think it *may* be the new nosecone holding the drive in an ever so slightly different position combined with a worn gear on the drive, and maybe also because I don't have the drive teeth meshing with the same teeth on the gear box shaft as before. Add up all 3 and I'm getting that weird binding.

New speedo drive is probably going to be aftermarket, I assume? Tempted to fab up a block off plate.

Speedo works/worked fine and everything was normal in that department before I took it apart. Two steps forward...

No, the speedo drives are not the same as the differential final-drive ratios are different between the 500 and the 126

 

[FIATinCA]

Thank you, just saved me a headache

 

[FIATinCA]

I’ve got a new speedo drive on the way from the UK. I’m kinda nervous it’s going to be the new nose cone that’s the problem, but here we go. Will update. Thanks for all the help everybody.