Clunk when hitting accelerator

Hey guys! I have a 2002 E825 and have been researching for answers. Our cart works good, but upon pressing the accelerator regardless of full stop or from a coast, there is a thump or clunk as the motor engages the drivetrain. Could this be caused by the “rubber bumper”? Or the inboard joints on the half shafts? Doesn’t affect performance- just annoying.

Is this thump coming from the passenger side up by the dash?

Chances are that is the main Contactor kicking in and perfectly normal.

On the 02 it first does the “clack” when you key on and brake off (no pedal press). I think it will kick back out(~15 secs?) if you don’t press the pedal, but will kick in again on pedal press.

Gotcha! I know that clunk it seems drivetrain specific (softer if I feather the pedal) it’s like when the motor is engaging and torquing the drivetrain it clunks and can be felt through the floor.

If torque specific then sure trans is not coming loose.
Check bolts on subframe where front clip attaches to car frame.
There are tabs at the bottom with only one bolt each side.

Jack up the front end and check A-arm bushings, ball joints, etc.

A worn out motor bumper is more of a barking nose on pedal lift than a clunk. Could be worn out input shaft. How many miles on the cart?

On my 2002 a new motor rubber bumper lasts maybe a month before it’s clunking again. I’ve been thinking of shaving down a 2nd bumper and start to stack them up.

That has it’s risks. Not quite like dropping a dime in there, because the bumpers do have some give, but little too thick and you could push the shaft out enough to put friction on the magnet or worse, possibly blow out the end bearing in the motor.

Are you using the squishy bumpers with 8 or 10 “splines” on them?

The smooth Polaris bumper doesn’t collapse as much or as fast. If you try one though, make sure you spin everything thoroughly by hand on the jack stands and really listen and feel for anything out of the ordinary.

I didn’t do that thoroughly enough when I put one of the Polaris smooth bumpers in and it put enough pressure back on the shaft to rub the magnet, over heat it, and warp it. This in 2 blocks of driving distance.

The bearing was damaged too, but might have been existing damage from previous owners useage

Thanks guys, I mean maybe it’s normal the best way I can explain it is when you apply power with the accelerator there’s a little “play” before the actual torque from the motor is felt is kinda like a click/thump as you accelerate. The cart has 2100 miles.

The first 2 or 3 were the “splined” bumpers and they hardly lasted a week. The last one I installed was one of the “smooth” Polaris bumpers and it lasted about a month before the clunking started again.

I’ve seen enough posts of burned up magnets to put great amounts of effort into only adding enough rubber to fill the void. I definitely need to look more closely at this issue and find a better solution than putting in a new rubber bumper every 4 weeks. The 2002 makes enough other noises that this start and stop noise is very anoising. :wink:

BTW, I had originally thought this clunking was a sign that my CV joints were toast. Eventually jacked up a side and turned the wheel while looking at the CV joints and noticed I was getting maybe 1/4-1/2 inch movement at the outer diameter of the wheel for very tiny movements in the CV joint and it was unlikely the CV joints were the cause of the clunking. Eventually pulled the motor and put in a new bumper and the joy of silence was experienced. For about a week but it was enough to ID what the problem was.

Do you want had a similar issue and it was the bumper?

Even the shitty ones should last longer than that…

I’m wondering if the clearances are off or you have a bearing that likes to walk.

Are the bumpers coming out just totally mashed flat?

Do you have an R4F motor or a D&D in there?

ya, pretty much.

Stock motor, stock transmission, stock input shaft. 7,500 miles and for lots of years it was a surf shuttle in OB where it had to climb 3/4 of the way up the Point Loma Ave hill with lead batteries.

Is blaming the rubber bumper in this case is the proper solution? This implies there is excessive axial movement of the armature. What do you think is moving the armature back and forth when loaded/unloaded?
Is the input shaft really walking in/out that much?

I understand that loading the armature will temporarily fix an alignment vibration due to worn out coupler and spline, and as you know- Too much load from too thick of a rubber bumper will overheat the outboard bearing in the motor. It is just not meant to be a thrust bearing.

In @barquey case here it almost sounds like excessive gear lash flapping back and forth.
When was the last time you checked/changed your oil? Maybe you should squeeze in a bit of 90wt in there and see if that gets rid of the hammer/clunk?

If I remember correctly, on the 2002 transmission the input shaft does not have a captive C clip to hold the bearing/shaft in place so all the forces of the helical gear will be on the rubber bumper in the motor coupling one direction and then it will be on the inner bearing in the other direction.