Low gear set from A999 installed into 904. Anyone experience gear noise?

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JoePole1

JoePole1

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Hey All. Like the title says. I pulled a low gear set from an A999 and gave it to my local builder to install into my 904 during a rebuild. I had read that the low gear set can be "noisy". Yes it is noisy. Odd thing is that it didn't start until I had a couple hundred miles on it. Has anyone experienced this and can you describe the sound for me? TIA.
 
Does it make noise in 1st, 2nd, 3rd and rev? I'm assuming just 1st & 2nd.
 
Just like a rear end ring and pinion when they get worn and the factory backlash specs go out of whack, they make noise.

New carrier bearings and races moved the ring gear back into spec and the noise of the rear end goes away. 2 full trips back and forth to Florida and is still rolling fine > no noise.

Same with your transmission, you have 2 different generations of parts that you are trying to match up. Gears are cut in different machine shops and different years and are off just enough to make noise.

Tear it open and get in there with the Yellow gear backlash paint to see the wear pattern mating surface of old parts to new.

Bet you see the Heal Toe contact patterns are off to an other than ideal position.


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Makes sense. Just odd that it took a few hundred miles before it started making noise.
Any thoughts on longevity? I can live with the noise for now. I have a 42RH waiting in the wings but it might be a year out.
 
If it's making noise in 3rd gear, it's not from the gearset because the unit turns as an assembly,
it can be from a bearing inside the trans or t/converter or possible rear end.
 
As for the longevity with a whining planetary, I had one that I ran for several years, and I later sold it that way. New owner blew up the slant some years later but the 904 was still happily whining. IIRC it was just Second. or maybe just First; I forget, I mean that was like 47 years ago. How do I remember the year? Cuz I bought that car just weeks before getting married, spring of 77; so help me I better not forget our anniversary. and the trans got my attention real quick.
I had taken that trans apart looking for the noise but couldn't identify it. Since it was just one gear, I didn't take it to the next level.

AFAIK there is only one ballbearing in a 904/727, which is used to steady the output shaft, out by the Speed-O area.

I also remember that the planetary whine is pretty distinctive.

I also discovered that when changing between the two gearsets, EVERYthing on the output shaft has to be swapped together. You cannot mix and match planetaries from an A904 onto an A998/999 output shaft. They are a matched set. ( EDIT; Actually, I think the change was at a particular year break).
I accidentally got this wrong, and within 30 miles the aluminum planetary had all the splines ripped right out of it. When I took the trans apart, I could not see a difference. Research revealed that to me.
Since I could not see the difference, I had to take another core trans apart, and this time swapped it all over as a set; problem solved.
 
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Messed with the car a little more today. Have a recording but can't upload. May have to do the YouTube thing. Anyway I get the sound in all 3 forward gears so I guess it's not the low gear set as moparlvr166 pointed out. It's an odd sound almost like a generator winding down as I coast and slow down. Kind of like Grrrrrrrrrrrrrrrr. Not a whine.
 
JoePole1 said:
Messed with the car a little more today. Have a recording but can't upload. May have to do the YouTube thing. Anyway I get the sound in all 3 forward gears so I guess it's not the low gear set as moparlvr166 pointed out. It's an odd sound almost like a generator winding down as I coast and slow down. Kind of like Grrrrrrrrrrrrrrrr. Not a whine.
Click to expand...

If the pitch of the whine doesn't change depending on what gear it's in I'd lean towards a bearing going out, especially if it's more of a "growling" sound kinda like you describe
 
I have heard a truck do the same sort of thing when the 727 output shaft bearing was worn out. It growled and was pretty apparent when you listened to the floor right below you. Tom
 
JoePole1 said:
Messed with the car a little more today. Have a recording but can't upload. May have to do the YouTube thing. Anyway I get the sound in all 3 forward gears so I guess it's not the low gear set as moparlvr166 pointed out. It's an odd sound almost like a generator winding down as I coast and slow down. Kind of like Grrrrrrrrrrrrrrrr. Not a whine.
Click to expand...
So, you only hear the noise on deceleration, how about normal accel and hard accel then steady speed at 60MPH? then tell us what you hear when driving steady 60MPH and lightly accel an decel up and down? Drive again and let us know when it happens.
 
moparlvr166 said:
So, you only hear the noise on deceleration, how about normal accel and hard accel then steady speed at 60MPH? then tell us what you hear when driving steady 60MPH and lightly accel an decel up and down? Drive again and let us know when it happens.
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Pretty much during decell at lower speeds but exhaust may be drowning it out. I don't hear it any other times.
Edit....I also tried in reverse but couldn't quite make it out. May still be there but faint if any.
 
JoePole1 said:
Pretty much during decell at lower speeds but exhaust may be drowning it out. I don't hear it any other times.
Edit....I also tried in reverse but couldn't quite make it out. May still be there but faint if any.
Click to expand...
So decell lower speeds and goes away in neutral, try in D range and slowing down and when you hear the noise shift into 2nd gear and see if you feel the downshift, if you can then we know it was in 3rd gear when noise started, now try manual 1st at 15-20 mph and lightly get off and on the throttle to see if it noise changes pitch or goes away and comes back.
 
moparlvr166 said:
So decell lower speeds and goes away in neutral, try in D range and slowing down and when you hear the noise shift into 2nd gear and see if you feel the downshift, if you can then we know it was in 3rd gear when noise started, now try manual 1st at 15-20 mph and lightly get off and on the throttle to see if it noise changes pitch or goes away and comes back.
Click to expand...
Thanks. Will be a while for further testing. Car is semi asleep for winter unless we get some good weather. I will try your suggestions.
 
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