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Gearbox Noise in 1st!! - Is this normal??

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NardisCNC

NardisCNC

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I recently put a rebuilt 4-speed stock gearbox in my midget, because the one in it got stuck in reverse. Instead of rebuilding that one myself, I found one completely rebuilt for about the same price it would cost me to do all the work myself, not even counting the time.

I pulled the engine, changed the trans, put everything back together.... it seems to function great. EXCEPT, when in 1st gear, it makes this LOUD whining sound, almost like the gear teeth are not meshing together exactly right. The other 3 gears are smooth as silk, and are very quiet.

Does anyone have any thoughts on what this could be?? Is this typical? I think the person who rebuilt it said he put a new gear-set in it. If this is the case, could the gear teeth need to "wear in" to any degree?? Thanks for any help!
 
Loud whine typical? Not in a re-built gearbox. Do they need to wear in? No, you have a PM.
Dug
 
Yes its normal, they are straight cut gears. In lots of newer cars they still use straight cut gears for reverse. I heard a new Toyota Yaris backing up the other evening and it must use straight cut gears for reverse. In the rib cage type 2nd, 3rd are synchromesh, 4th is a straight lock from input shaft to output shaft,but first is straight. It also makes it harder to gear down into, don't force it, just use second. Here is a picture of the cluster gear or Laygear as the brits call it. You can see the difference. The larger gear on the end is in constastant mesh with the output shaft. The other 3 make with the input shaft at different times. That little one with straight teeth is used for 1st and reverse.

MGAcluster.jpg
 
I'm going by the use of LOUD whining noise. No that's not normal, not normal at all. Some noise because it's straight cut? yes.
Dug
 
All the gear noise is kind of amplified with the top up and not much real insulation in a spridget. Even the 5 speed with all synchro gears makes some whine with the top up that you don't even notice with the top down. I remember my mini with the 10" wheel would really whine and everybody said that was normal for them. Diff gear whine is transmitted back through the short drive shaft as well. I did everything I could to make mine a kind of quiet cruiser type with the super high gearing and all and it still has more whine than I would like but its night and day different than the old 4 speed and 3.90 gear. To your point Dug, I guess it depends upon what Loud really means. With my old setup and nothing really wrong, it was really whiny with the top up.
 
Mine has a noticeable whine, but I wouldn't call it loud. On the other hand, someone accustomed to driving a Lexus might call it that. So, it seems that the best thing would be to have someone else, who has some experience in these things, listen to it.
 
Ah.
What does "rebuilt" mean?

Used to mean a new valve cover gasket and repainted valve cover!

That said, a "rebuilt" replaces bad parts.
One "new" gear against an "old" gear can give you quite a noise until they "seat".

How noisy is noisy?
How long do you want to give it to "seat"?
 
Sarastro said:
it seems that the best thing would be to have someone else, who has some experience in these things, listen to it.
Click to expand...

I actually did just that - He though it was definitely not sounding right. And compared to my previous gearbox (the one that locked in reverse) this one is much Louder in first.

TOC said:
One "new" gear against an "old" gear can give you quite a noise until they "seat".

How noisy is noisy?
How long do you want to give it to "seat"?
Click to expand...

This very well might be the case also. I know its relative to several factors, but how long could this take?

Both of these are ribcases we're talking about by the way.
 
TexasSprite said:
I have a rebuilt ribcase in my Bugeye and it is dead quiet in first gear. Perhaps excessive laygear play?
Click to expand...
Maybe you got more insulation or something but I never seen any of the Mowogs that were quiet in first, especially when you wind it up a little. Its the nature of straight cut gears to whine or maybe there is a replacement set of gears that have a different mesh or something.
 
could it be something as simple as low fluids?
 
I also have always found Spridget boxes to be "noisy" in first, especially with a bit of wear on them, and I too would suggest trying a heavier (but not MUCH!) lubricant as a first step! I don't know what the consensus here is re: additives, but on old stuff I have found Lucas (not the Prince of Darkness one!) Oil products to help!!.
 
TexasSprite said:
I have a rebuilt ribcase in my Bugeye and it is dead quiet in first gear. Perhaps excessive laygear play?
Click to expand...

I've been in the passenger seat and driven Mikes sprite it is a very quite tranny.
I had a rib in mine just like Mike and it was worn out.. and very noisy.
I now have a 210 w rivergate it was rebulit by an expert and it is "dead" quite.
So with that all said they are both quite IF they are in top forum.
I would have to say rebulid is defined as a unit that has had all the wear items replaced and reassembled by expert.
 
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