Noises in 1st 2nd 3rd gears No noise 4th 5th

[harvfiat1]

I am trying to get validation of the noises in my 81 Spider. If I do a tear down
Should I replace layshaft bearings to tame the roar present in all gears below
4th. 4th and 5th are totally quiet. While in 2nd and 3rd gear there is a pronounced
Noise which goes away by engaging the clutch.
Can anyone point to what might solve my noise issues?
Thanks for Helping
Harvey

[124JOE]

well as i had my tranny rebuilt twice i can tell the story,
the first one i had when i got my car had no 2nd gear"kept poping out"and had the howl.
so i had it rebuilt,it had 2nd gear back but it still had the howl and at hwy speed the tranz was getting hot.
so i took it back to the shop. he said i need new bearings in it,and he pulled it back out.only to find a cracked case!
i got real lucky and found a parts car that had a good case, so i had that one rebuilt by a different guy.and he didnt want to use any
of the parts from my bucket of tranny parts not even my brand new 2nd gear. that was 16 years ago and i have about 3000 miles on
it since. but still love my car.
the howl goes away in 4th because its a 1 to 1 gear the motor goes around once and the wheels goes around once
so there's no heavy torque riding the gears,like 1st 2nd and 3rd

good luck.joe

[wizard124]

To borrow from Forest Gump...."a transmission is like a box of chocolates, you don't know what you are going to find!"

My hobbyist opinion is I think you are on the right track regarding the layshaft (countershaft bearings) being suspect. My Fiat factory transmission booklet states (regarding fourth gear engagement), " As a result, there is a direct drive from the input shaft to the main shaft, giving 1:1 ratio. The countershaft continues to be driven, but does not transfer power." Having no load on the countershaft probably explains why there is no noise in fourth gear. But, the countershaft does transmit power in fifth gear. Perhaps, the load is far enough away from a bad bearing that the noise is not an issue.

I dismantled mine because of a 4th gear syncro problem. While I was in to it, I found this:


I replaced it as a precaution even though the bearing seemed to spin smoothly. During your teardown and inspection, you will probably want to replace more than just a bad bearing or 2 while you have the opportunity to do so. Using calipers, you can compare the syncros to one another looking for evidence of wear.

I considering the overhaul of my 5 speed one of my rewarding processes. This is my thread: http://www.fiatspider.com/f15/viewtopic ... t=4th+gear

[vandor]

Likely bad front or mid layshaft bearing, but a teardown should tell you anyways. Any time I open an old transmission, as a minimum I replace the 1-4 synchro rings, their springs, and the shift forks if they show any wear. The rest you can replace based on condition and budget.