# grinding on deceleration?



## Ziggythewiz (May 16, 2010)

What kind of motor and controller do you have? Do you have it setup for regen or plug braking?


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## Newbiee (Feb 16, 2011)

im on 96volts with 9" fb1-4001 and an open revolt. No regen or plug brakes.


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## Woodsmith (Jun 5, 2008)

Is your motor coupler fixed to both the trans input shaft and the motor shaft?

It should be fixed to the motor but free to slide on the trans on the splines.

Alternatively the two shafts could be touching inside the coupler and on the overrun the helical gears in the trans are applying an axial load on the input shaft making it push on the motor shaft.

Did you check the bearings in the trans before assembly? A loose bearing could also make some noise on the overrun.


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## Newbiee (Feb 16, 2011)

yes the coupler is fixed to the motor shaft with a key, set screw, and center shaft screw. Its free on the transmission shaft, only engaged from the splines. 
In simple are you saying the vehicle load on deceleration can push the drive shaft and transmission forward and therefore hit the electric motor shaft?


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## Newbiee (Feb 16, 2011)

sorry by the way my EV is rear wheel drive, so it has a drive shaft.


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## Guest (Feb 1, 2012)

Could be that the u-joint is toast, Trans could be toast, Touching is possible on deceleration. Maybe a bit premature on taking to DMV don't you think!

Anyway check your hard parts to see if anything is loose. Driving it a few times can loosen up things. Could be a noise that has nothing to do with your trans or motor or adaptor. I found a problem on my MG that I thought was the differential and it ended up being a stupid piece of metal bracket touching the inside edge of the rear wheel rim. 

Pete 

What car did you convert? Only 96 volts?


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## Woodsmith (Jun 5, 2008)

Yes, worth checking all the way along the driveline for worn or loose bearings, splines and UJs. Also look at suspension bushes as on the overrun a live axle will try to go nose down and that could lead to a UJ complaining. It is worth checking the UJ alignnment on the propshaft too.

With an EV, as there is no noisy engine, sometimes wear and tear noises in the drive train and suspension becomes more apparent.


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## Newbiee (Feb 16, 2011)

i was able to test a few things today, but am still not sure what exactly is going on. I put the rear wheels on jack stands and acceleration + deceleration is very smooth so no problems, and no grinding while in mid air. Then i tested the gears to see if my transmission is any good. Gear 1,2,3 and reverse gear, all grind badly during deceleration on the ground. But gear 4 didn't seem to have any grinding. Gear 5 i didn't get to test as i don't have enough power but i assume it would act similar to gear 4. Could this mean my transmission is no good? i did get it from the junkyard after all.


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## EVfun (Mar 14, 2010)

A couple of thoughts. 4th gear is likely direct drive in the transmission. Grinding in the other gears but not 4th can indicate bad bearings in the transmission, either on the counter shaft or on the input shaft. It can also indicate a worn out pilot bearing in the flywheel.


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## Woodsmith (Jun 5, 2008)

Agreed. 

Sounds like countershaft/layshaft in the transmission.
In all but 4th gear the layshaft takes a lot of axial loads due to the helical gears. I would suspect that the taper roller bearings are worn, or sloppy for some other reason.
Generally they are taper rollers shimmed to preload or plain bearings with a thrust bearing that is shimmed.

Either way it is likely to be a bearing problem there.


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## Newbiee (Feb 16, 2011)

I would like to thank you guys again for your help. Today i drove my EV to the BAR referee it was about 25 miles round trip. I got to drive on the big streets reaching much higher speeds around 40 and 50 MPH. About halfway there i noticed the grinding on deceleration disappeared  shifting got smoother and driving my EV became a pleasant experience.  If i am lucky hopefully it stays that way, maybe it just needed to be broken in? This and getting my stickers to legally drive my EV is the good news. Yay  

But here is another problem that drew my attention after no longer dealing with the grinding. I am stumped again on this one, using 1st,2nd, and 3rd gears my EV makes a very loud whining sound. It has always made this noise, i just always thought it was normal. Until now of course because i found 4th gear is completely silent without a whine. The whining starts as soon as you go, its not intermittent, its always whining whether deceleration or acceleration. EXCEPT 4th gear of course. The car sounds like a jet from the drivers seat, im not sure what it sounds like outside the car. It is loud enough to overpower the radio. It's not the same as the notorious controller whining sound, i used to think it was just the way an electric motor sounds, but its not that either.

What could be making the whining that wouldn't happen in 4th gear?


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## EVfun (Mar 14, 2010)

No gears are carrying any load when you are in 4th gear. Here is a diagram of 4-speed, a 5-speed is typically similar, and both usually have 4th gear as direct drive.


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## Woodsmith (Jun 5, 2008)

4th gear is a direct drive connection through the gearbox with the gears cogs free spinning.
Any other gear, including 5th loads the gears in the layshaft and is usually a bit more noisy then 4th. However, in an ICE car the noise of the engine drowns out the nose of the gears.

Yours could still be wear in the layshaft, and needs a bit of investigation.
Have you checked the oil level and the condition of the oil?
Maybe draining it and checking for bits of metal will give some good clues. There may be a magnet in the drain plug but otherwise you can drain the pil through a fine cloth and then check the sludge with a magnet.


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## DJBecker (Nov 3, 2010)

It could be the layshaft/countershaft bearing set, but don't rule out the motor adapter plate and coupler being the problem. If you had no noise from the transmission prior to conversion, I would check this first.

On many transmissions the input shaft has a single large ball bearing where the shaft enters the case. Using a ball bearing allows a small angle misalignment without binding. The outer end of input shaft is positioned by the pilot bearing, and the inner end often supports one end of the output shaft with a needle bearing.

If your input shaft is significantly misaligned by an offset motor center, or the coupler is out-of-round, you'll both put high pressure on the bearings and get noise from the imperfect, high pressure gear mesh.

This the reason that the factory transmission bell housing to engine interface has dowel pins or sleeves. The alignment needs to be precise, not just close. When you use a custom adapter plate it's common to omit the factory alignment features so that fine adjustments can be made during assembly and testing.


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