Downshift Clunk!!!!

Hello-
Just found this sight. I'm stoked thought I was the only VX lover around.
I got a question- I have a downshift clunk, which happens everytime I depress the brake following downshift, when deaccelerating when I slow at lights. Most common in city driving.
I had it in twice to the dealer. My mechanic who is on it John Roscoe @ Isuzu in Reno (Guy is great), has looked at it, twice. Replaced applied band solonoid. I had the tranny fluid dropped prior and replaced with Mobil 1 ATF. Which definitely made my tranny drive smoother. Mercon would have worked just as well probably.
Anyways I took it to the Martin Isuzu dealer in LA and he said it probably is my drive shaft yoke(?) which has to be aptly lubed or it sticks. Any body out there know what it might be. I am taking it in but given it has been in twice already with know resolve I'm getting bummed. Knowledge and suggestion would be great-

Glad to be on the list
happy holidays
xdfarrx

The noise is the tranny shifting from 2nd to 1st and is present in all VX's. It is considered normal unless the noise and or feel is extreme.. You say you have it everytime you brake, that could very well be a yoke clunk but, you would usually hear it on acceleration also. Hmmmmm....


Glad to see you aboard with the rest of us..

Like Scott said.. sounds like the natural downshift unless it is really jarring

Thanks for the responses- This is not a downshift clunk. I understand the tranny is a little 'hearty'. This is not in the tranny, from what i'm inferring here. This(clunk) follows after the tranny has downshifted and after I have come to a stop. It follows right after I release the break and roll/accelerrate. It sucks. I have had the trnny looked at twice. From what I think it is in the drive shaft.....I don't know I am frustrated. I go in to my dealer to take it back. Considering we have done this twice on the tranny, I have been told the drive shaft yoke can stick? and it has happened on the Amigo Sport and on another VX per the service manager in LA (Martin dealer)
....wish me luck-

Quote:

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Originally posted by xdfarrx
This(clunk) follows after the tranny has downshifted and after I have come to a stop. It follows right after I release the brake and roll/accelerate.

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Mine does this, too. It feels like something is binding when I stop under moderate to hard braking. If I throw it into neutral while stopping, or even after stopping, it doesn't seem to clunk. That leads me to believe it's something in the transmission/converter. I'm having the dealer take a look at the drive train when I take it in for the 15K checkup next month. If your dealer finds anything in the meantime, let us know. If I learn anything I will pass it on.

I have the same effect if I put into nuetral. As I said before I had them look at the tranny with nothing found or disclosed. My mechanic inferred it was the band applied solonoid which I guess asssts downshifting in the tranny? I am suggesting the driveshaft yoke, or torgue converter. The clunk is more then noticable and has over time become more pronounced. Good luck with yours. I am taking mine in following the new year to get worked on. I will let you know what is figured or better, resolved.

I think if the VX experts would read this they would agree.. We all have it.. I do. Its a normal Isuzu thing I was told. Just as you described it - after letting go of the brake - after stopping - clunk.

not to worry

But if it worries you, do take it in for a look.

Not to discount your comments Anita, I don't think it is normal. I have driven another VX with no such 'lash' or clunk. My mechanic as well another Isuzu mechanic noticed it as well, and were not able to resolve it. I live an hour from my dealer so I haven't been able to leave it with them long enough to figure it out. I will let you all know what happens as I'm going in to get my driveline looked at from A-Z, after 2003 starts.

It wouldnt be the first time I was wrong.....;pr;


:flame:

Give the mechanic as much info as possible. Try to find more than one situation that causes the sound.

Park it, Get under it and try twisting/ wiggling the driveshaft, inspect U- Joints while down there. Put it up on stands. In Neutral, check rotating assemblies / steering / suspension for freeplay.

You should be able to do the moving tests slow enough to keep your door open, which might help isolate the source of the clunk.

Find an empty, poleless lot.
Leave it in First or Low 1 and see if you can get it to clunk while switching between light accelerating, to lifting off pedal, to accelerating. Try it while lightly applying the brakes too. Don't exceed 15 -20 M.P.H.

In a wide open empty lot, in Drive, lift your foot off the brake and let the truck move at idle speed 5-10 M.P.H. MAX! Without using accelerator, shift into Neutral till speed drops a little, then shift back into Drive....any clunk? Long delay before Drive re-engages?

You could try a mini Reverse Drop. Again, in Reverse , Idling , lift off brake ,let it just start rolling NO MORE THAN 1/2 M.P.H. then shift to Drive..... listen for clunk and check delay between Reverse and Drive.

Disclaimer: Do these at your own risk!

Just trying to provide some additional scenarios to produce the same clunk for you and your mechanics evaluation .


So many possibilities. Have you tried changing Power or Winter modes? Does it happen every time, always? Has the mechanic checked the trans. pressures? Convertor Lockup and Unlock? Have you been offroad? Missing alignment shims/ worn suspension bushings can cause suspension or steering component freeplay that could clunk on braking or accelerating. Heck, it might even be the T.O.D. unit or its' computer.

Write down exactly what situation(s) cause the clunk, to help the mechanic reproduce it.

Good luck and let us know how it turns out.

Delayed Downshift is the term for this problem....:coolg:

I had this problem over a year ago...
mine got so bad, after coming to a stop, (and being stopped for up to 30 seconds) then releasing the brake and applying gas caused a loud thump/harsh downshift from the last gear.

After taking it to the dealer 2 times,:argue: they finally figured out the line preasure was way too high.... so they asked the isuzu warrenty folks, and they opted to just replace the whole tranny with a new one,

The new tranny works much better and does not have the "delayed downshift" that the old one did
It does still downshift firmly, sometimes even with a small 'clunk' noise. I feel this is normal....

good luck


Allan
99 VX on 35"s

Big thanks for the feeback- Really cool. To last postbigger thanks...They should handle it.I am going to bring all this with them Isuzu folk down in Reno-
Knowledge is strength and strength is.....er, a smooth VX

The simplist fix for your problem would be to anticipate your braking, I have this as well as others but find it only happens when I brake hard in a short distance. If I slow roll to a stop after antisipating where I need to stop there is NO CLUNK, if I stop hard and short I get the clunk.

I believe this is normal and can be avoided if it bothers you , just adjust the way you brake is all :D

As you can see we have an owner with a brand new tranny and the same thing happens to them as well.

That's my .02 worth :)

Vehix-
Thanks. I am aware of this. I also can shift into nuetral, on braking to prevent this as well. Where I live in the winter I drive very little, and the nature of driving is mellow. In the summer I drive down westside of LA. Quick go and quick stopping. City driving is where it is worse
I am going to have my line pressures checked and it seems there is a common issue in our trannies especially in the 99' which mine is.
Kind of sad having to adjust my driving to offset this. Especially with the weaponry we have for brakes. Poor little guys just want to get used- and should...
thanks for the suggestion

After a second trip to the dealer, I have nothing constructive to add. The first trip was for my 15K service on Saturday, but they didn't have a tranny expert on site to diagnose the problem. I brought it back today and the tech hooked it up to his computer. All of the line pressures were within spec, and no error codes were displayed. I took a ride with him and then I drove for a while trying to duplicate the thunk. It wouldn't do it! The tech concluded that there was nothing wrong with the transmission and what I was feeling was rear axle wind-up. Doesn't the VX rear suspension design preclude this from happening? He did confess that the Trooper had a problem with binding drive shafts, but the VX has a different design that doesn't bind. He did shoot some grease into the shaft while he had it on the lift, but said the grease that squirted out was still good. I greased it at 7500 miles and asked if I had possibly used the wrong type of grease. He said it was OK. SOOOOO... Until someone can come up with an Isuzu recall or TSB there's nothing he can do. At least I have it documented.

Attn Cobrajet-
My clunk was not the tranny...it was the driveshaft splines binding. Apparently the grease was working less then it was supposed too and the tolerances which are spec'd very tight were to tight. Therefore they were binding, and I got that god awful clunk, post braking which drove me nutz-
Ask for an A-Z look at the driveshaft. You should also find my last post immiediatly following my service with the diagnosis. I brought in a couple copied emails from the Forum and it seemed to help my Master Mechanic get it isolated and fixed. Tranny works killer now, and I'm going to that autotrans Interceptor to make better use of it.
Good luck an holler at me if you need any other insight-
peace

Since I took mine back the second time I have not been experiencing the clunk as much, or as severe. The tech did say that he shot some grease into the U-joints and splines, but said they had enough grease in them. I suspect that the grease I used was not compatable with the factory stuff, since it seemed to start shortly after I performed the 7500 mile service. I'll buy some new grease that matches EXACTLY the specs from the manual for my next service. Your solutions would support my theory. Thanks for the follow-up; I did note it in the other thread.

Greg-
My tech said that the grease was not working sufficient??? And he checked the tolerances and said they were way to tight, despite his first diagnosis(pull, twist, and turn I think), and had to get into it to check some shims?. He ended up replacing the entire U joints and my stuff has been money since. No clunk and my tranny shifts sweet-
Great to hear your clunk is going away-whatever works-