Any ideas?

[startech47]

My son's 1979 Midget 1500 was quiet after restoration, but now has a whine when driving. There are only a few miles on the car since it was restored. There is no noise in reverse, 1st, or 2nd. There is a slight whine in 3rd and a louder whine in 4th. I'm trying to determine if it is the rear or the transmission. The transmission was rebuilt (new bearings, syncros, and gaskets. Nothing was done to the differential. Does anyone have a differential and/or a transmission for sale. The differential ratio does not matter as I am planning on using it to test by substitution. Easier to change the rear than to pull the engine. If it's the transmission I was thinking maybe the rear bearing has gone bad. Thanks for any ideas. Phil

 

[Stick]

You shouldn't need to swap the diff to see if that is the cause of the noise. Try various gears at a constant speed, if the whine goes away or gets worse then I would say the problem isn't in the differential because it is moving at the same rate at a given speed regardless of what gear you are in. Same goes for the output shaft on the transmission as a matter of fact.

I have a similar problem on my car, most pronounced in 4th but sometimes present in 3rd. Also, in my case seems to only whine under acceleration. I know my transmission needs rebuilt anyway so I haven't worried about it since I'm in the middle of swapping in a new motor/trans anyway.

Sorry I don't have a solution, although I imagine it is a common issue. Hopefully I can at least help you rule a few things out.

 

[recordsj]

have you checked that the fluid level in the transmission is full?

 

[jlaird]

Aye, check the fluid level first.

 

[startech47]

The levels in both were correct. I'll re-check both and check for metal flakes as well. Last time the car was on the road was in the fall. As I remember the whine was loader with increased load. I'll check that as well.

 

[radibob]

The whine is louder in 4th than 3rd because you are going faster. Same thing with it only being audible on acceleration because that's where the wear is in the differential. Classic case of worn diff.
The good news is that it will go FOREVER like that if you can stand the noise. It's difficult to find a used one that won't whine. What I suggest is to warm it up and drain it, then fill it with a good grade of SYNTHETIC diff oil, like Red Line if they make diff oil. This made a huge difference in mine.

 

[Mio]

fill it with a good grade of SYNTHETIC diff oil, like Red Line if they make diff oil.

Red Line does indeed make a synthetic differential oil.

Red Line 75w-90

Mike

 

[bgbassplyr]

Whine in 4th is diff because trans is straight through, no gears pulling against each other.

 

[startech47]

Thanks for the latest comments. I'll try the drain, refill, and another road test. I am leaning towards the rear since the trans was rebuilt. In fourth there shouldn't be much load on the output shaft bearing.