thumping under brakes

[matmce]

Hi All
I have been reading with intrest as i have a 07 D40 Auto and recently notice a thump/knock when stopping. I thought it was just something rolling around in the back but after this reading this I'm concerned. For me this is only very recent so i havent been able to pinpoint exactly when this happens. I am intersted to know if the noise happens after the truck is hot or does it happen first thing in the morning when everything is cold.
Regards
Jacko

 

[Connaught]

matmce, mine happens at both, after a run home from work and pullin into the garage, or just moving it out of the garage

keep in mind that mine is a manual

its an '07 with 155k on the clock

to be honest i am not that super worried about it, if it was something moving around i would expect something loose underneath - which there's not, of it was a driveline issue i would expect a problem when the vehicle is underway,

this all being said i also don't intend to ignore it

investigations continue

 

[matmce]

maybe we need more people with both auto and manual trucks, with same problem to reply with their story to eliminate whether its an auto or manual issue!!
If suspension problem, i am soon to upgrade my origional crap setup (with airbags) to a 2" tough dog all round lift with medium springs in rear. If the problem is a suspect shocker, this should (in theory), stop the problem. I have about 3 weeks (before i get the much needed suspension)to investigate with my set up at the moment.
P.S. My baby has 125k on clock.
I will monitor this thread with intrest!!

 

[ericcs]

did a few checks yesterday. at first i turned off the O/D and it didn't seem to do it as bad, the went back to normal and it at first it didn't do it, but was back with a vengeance by the time i got to work.
this morning it did it as normal either cold or hot, in either 2nd, 3rd unlocked or locked in D. if i move off for a distance without touching the throttle then brake it doesn't do it.
don't understand why it dissappeared for 12months, have changed any oils in either gearbox or diff
you can't hear the thump, only feel it. i can brake hard to a stop with no thump, then while completely still, let the brake preasure off a bit, thump, let off bit more, thump, off the pedal completely, thump again as i roll off.

 

[Old.Tony]

I wonder if it's a brake thing. I remember when I stopped hard on my motorbike the front suspension would compress heavily and the rear would extend. When I came to a stop, the bike would have a nose-down attitude until I released the brakes.

I actually think your rear brakes might be coming on a little hard, if it's doing this to your car, AND your pads are "grabby" on the rotors, possibly there's some uneven wear on the disks.

What MAY have happened for 12 months is your REAR brakes weren't grabbing as hard, possibly due to the load adjuster, and now they are again - possibly something changed with the load adjuster again. I don't know - all I can think is that from what you describe with releasing the pedal AFTER you've stopped, it sounds just like my motorcycle used to feel when I held it in its nose-down attitude when braking hard.

In fact, this happened on both my FZ Bol d'Or (1977 CB900) and my FJ1200, now that I think about it.

So the big question would be this: when you stop like you describe, as you release the brakes, does the attitude (level) of the car change?

 

[Connaught]

i only brought up the brakes cause in my case it consistently happens when i pull into the garage and 'thumps' just after i stop the car and push in the clutch,

only brought it up cause my old civic did it after the brakes where done

 

[ericcs]

i'll check tomorrow and see if the attitude of the car changes once i let the pedal up. might even manually adjust the rear brakes as the handbrake comes up a fair way. i did do this as a trial before it went away last year, just don't recall it fixing the problem

 

[kempseyken]

I also think it could be rear brakes , mine does something similar and pretty sure its rear brakes and one day I will get around to fixing them but not that much of a problem yet.

 

[joe2006]

Mines an auto & I do hear a thud occasionally. I hadn't bothered posting a response until now because it doesn't worry me but seeing as you asked...

In my case it certainly doesn't seem sinister, not like many of the possible causes suggested anyway.

 

[matmce]

did a few checks yesterday. at first i turned off the O/D and it didn't seem to do it as bad, the went back to normal and it at first it didn't do it, but was back with a vengeance by the time i got to work.
this morning it did it as normal either cold or hot, in either 2nd, 3rd unlocked or locked in D. if i move off for a distance without touching the throttle then brake it doesn't do it.
don't understand why it dissappeared for 12months, have changed any oils in either gearbox or diff
you can't hear the thump, only feel it. i can brake hard to a stop with no thump, then while completely still, let the brake preasure off a bit, thump, let off bit more, thump, off the pedal completely, thump again as i roll off.

I did a few checks today, and i could only manage to feel a very very light thump similar to what you describe but not all the time. I wasn't able to check with O/D off and in nuetral only because in my case it is so faint and too hard to get it to do it all the time.
My thoughts about this were also tending towards a rear brake issue but i am not to concerned as it is only minor me. Thats not to say that its not important.

 

[ericcs]

manually adjusted the back brakes up 10 clicks on each wheel,didn't appear to help

 

[Old.Tony]

What happens if someone moves the front of the car up and down while you hold your foot on the brake (not driving, engine can be stopped)? I'm wondering if it's suspension related.

 

[ericcs]

another twist, if you braking to a full stop and you let the brake off momentarily, then brake again to a stop, it doesn't appear to do it. this may be related to my earlier comment which was if you have stopped, the let the car roll off(auto only) for a distance then brake to stop again, it doesn't do it. pattern seems to be that it needs to be accelerated off first

i took the brake drums off when i adjusted them, and everything looks fine, the pads have about 5mm all over. no sign of anything moving around under brakes.

can the handbrake be adjusted, can't find any adjustment point anywhere

 

[Connaught]

i would suspect that there may be a bit of 'play' between the shoes and the carriers, or the brake adjuster springs may be worn out, (i have determined that mine has new front brakes, but no idea when the back brakes where done, should probably look)

i am thinkin along the lines that mine has 160k on it tho, your worn out parts may or may not be there,

 

[ericcs]

can't help but think it's something in gearbox/torque converter. if you start braking for a full stop then take your foot off all together, then brake to a stop, it doesn't do it. same as if you brake to a stop, get it to thump, then roll off for a distance without accellerating it also won't do it. seems to need a hit on the throttle to get it to thump.
car is going in for a new pinion seal on friday, so have asked the experts to check it out

 

[ericcs]

had the pinion seal done yesterday, and although i have only done a few k's, so far it seems not to thump. so, it could have had something to do with the backlash, or, apparently the diff oil was contaminated. appears to have sucked in some muddy water, not that i can explain that one. is it possible the lsd could have something to do with it?

 

[Old.Tony]

Yes.

If you're braking hard, the front dives, the rear rises and the transmission stops with the car in this awkward position. As you release the brake, the transmission will move slightly as the brakes release their grip and the car settles.

I hadn't thought it could be the diff but there you go. Keep us posted if it comes back!

 

[Connaught]

just to throw a twist at ya

mine last night seems to be reliably thumping when i depress the clutch

while upshifting through the gears (may be my driving style) and particularly while i am easing the car into the carport and trying to miss the missus' car and the carport

seems to be getting louder too

but back to one of my original theories, it is due for a 160k service and i am going to be changing all the oils shortly (time how do you find more of that?)

 

[ericcs]

Yes.

If you're braking hard, the front dives, the rear rises and the transmission stops with the car in this awkward position. As you release the brake, the transmission will move slightly as the brakes release their grip and the car settles.

I hadn't thought it could be the diff but there you go. Keep us posted if it comes back!

it's back with a vengeance allright, shaking right thru the car. if you get the heavy braking out of the road just before it comes to a stop, it won't do it again untill you've accellerated off for a bit. maybe the lsd? who knows. just picked up my mix and match suspension package from zordo, hope it might take some of it out

nice friendly bloke that zordo!

 

[Connaught]

i changed the oil in my rear diff and the thumping went away for a bit, (i noted that the diff was pressurized) later it came back also with a vengeance, so i have taken the diff vent out (again pressurized) - there is a spring in it that forces the diff to maintain slight pressurization, but my vent was actually stuck closed, i have unstuck it, and refitted it and the thumping is gone, (i am modding the vent to put a hose up to near where the front diff vent is)

take your vent out and see if there is a hiss of escaping air, its on the right side of the axle halfway between the rh wheel and center housing looks kinda like a mushroom, when you get it out blow through it and see if its restricted