noisy box

[Alain de France]

hello to everyone
since I got my 1974 Fiat 124 spider (5 years ago) I have this problem
the gearbox makes noise on all speeds except on the 4
it’s a noise like on an old tractor!!
I changed the bearings and added a shimming washer that was missing, but it still worked

so I bought another box 5 and I revised it (also new bearings)
but to my great disappointment it does exactly the same thing
always this noise of gable; except on the 4
does that do it on yours too?
thank you in advance
and sorry for the Google translation

 

[carl]

You should probably go over to Mirafiori.com since that is sort of the 124 web site. My experiences with my spiders is they don't have the quietest gearboxes.....part of the charm of the car! Fourth gear is probably a 1 to 1 gear and would be less prone to making nose.

 

[Alain de France]

thank you Carl for this information
I am going to go see

 

[kmead]

thank you Carl for this information
I am going to go see

Sadly I believe this is a function of wear on the gear set. My 124 SC is reasonably quite in the lower gears and has an unpleasant whine in 4th and 5th

 

[Alain de France]

for me it’s the opposite; more noise in 1,2 and 3
not at all in 4 and a little in 5

 

[fiatfactory]

124 type transmissions, as a general rule, being noisy in all gears but fourth indicates an issue with the constant mesh pinion. The CMP is the gear attached to the transmission input shaft, and as the name suggests is "constantly" in mesh...

For fourth gear however the drive does not do the "dog leg" and transmit rotation to the secondary shaft, the CMP gets locked to the output shaft and the drive is transmitted straight through, in a 1:1 ratio - direct drive. This is why any issue with the CMP and it's mating gear on the secondary is a noise in ALL gears except fourth.

The CMP can "burn" if the oil level in the trans drops low, plus...just to confuse the issue.... mixing and matching CMP's can lead to issues with there being differences during production that are hard to notice if you don't know what to look for (if mixing and matching parts from two transmissions for example)

SteveC

 

[BEEK]

I also find the layshaft bearings and sometimes the needle bearing under 4th being the issue too.

 

[Alain de France]

hello and thank you for your advice to both of you
Steve tell you about this piece?
to my knowledge there was no 'mix' of pieces
what is the solution, replacing this part would be enough?