[phid_bombadier]

My half of an ATF drain/refill helped out my drivetrain thump from a stop and start, but I think I've discovered what is causing some of the residual thump.

(This ignores the slip joint re-lubing, which I think may contribute some as well.)

What I noticed this morning, upon cold startup the idle surges way up over 1K and as it gets warm starts to settle around 1K.

I'm expecting the idle to fully settle at 7-800RPM when fully warm. I drive about 35 miles to work in the AM and when I got to the local streets near work, my idle is still hovering up above 1K (slightly above). This seems to be causeing some drivetrain stress as it basically feels like while I'm braking, the gas is being pressed at the same time. (Which I'm not actually doing.)

If I put it in neutral, Thunk. If I put it back in gear, Thunk.

I'm going to clean the throttle body this weekend with some carb/injection spray and see if that does anything.

Anyone have any ideas on what's keeping the idle that high even after 30 minutes of highway driving?

I don't have a lot of data points yet so I'm not sure how weather dependant this may be. (Additional alternator load should not bump the idle up right? I'm talking headlights, defrosters, stock radio, and heater blower.)

 

[Amigo-2k]

Throttle body would be my guess too. I would also yank the EGR and spray that out too.
-Ryan

 

[phid_bombadier]

So I cleaned out my throttle body, idle solenoid (above throttle body), PCV valve, and EGR. Used a good amount of O2 friendly throttle body cleaner.

Idle is much more consistent now and does not idle high when it's warmed up.

I'm still having that drivetrain thump when coming to a complete stop and starting from a stop.

What I noticed is that when things are cold (first thing in the morning) there is no thump. When things are all warmed up then the thump comes back.

The thump is more prevalent on fast stops and when you do anything but a gradual start.

Anyone else experience this? Any other ideas?

I've heard that regreasing/packing the slip joint may help this, but I'm not sure where that even is, nor how to repack that joint. If it's the joint, is it really moving that much that I should hear/feel a thunk? Is something shifting out of place?

Any help is appriciated.
Thanks.

 

[phid_bombadier]

Update:

I just went out to lunch with 3 of my co-workers. So we have 4 x 200+lbs guys in the Rodeo.

Very little to no thump unless panic/fairly hard braking. Still slight thump on starts.

Basically much less thump.

This leads me to believe that this is driveline related, not tranny or throttle related.

Slip joint? (whatever that is)
Thanks.

 

[2eyefishclaw]

update on thumping Rodeos
first try claen and lube driveshaft splines if not useful
new info claims a trans band adjustment will help have not tried it yet but will as soon as I get a chance at that time I will post an update on it

 

[Amigo-2k]

Have a TSB or some special isuzu number for the thump thing? My dealer quotes it as being normal

 

[phid_bombadier]

I'm going to replace my shocks this weekend to see if reducing the dendancy to nose dive on braking will help reduce the driveshaft thunk.

Will keep you posted.

Oh, is there some sort of spring inside the slip joint? Something to keep pressure on the driveshaft to minimize on the foreward to back movement? (but still allowing motion)

From what I'm reading, it's just grease. Thoughts?

Thanks.

 

[¡Oracle!]

It is fixed on either end to your transfer case and your rear axle.

It only moves when the axle moves.

The thump comes when the slip joint binds and suddenly lets go as the axle moves upward or downward.

The shaft should extend slighty when braking and compress when accelerating as the tail rises and descends.

If you have ever repacked a CV joint this sounds far easier. I'm going to do mine in a few days.

The joint is located under the rubber boot that covers the portion if the driveshaft near your transfer case.

You need to separate the drive shaft to expose all the splines to properly clean them up.

 

[phid_bombadier]

I replaced my stock shocks this weekend with Monroe Sensa-Tracs.

This helped with the driveline thunk as there is less movement upon start or stop.

I definately need to clean and regrease the slip joint.

Does anyone know where to get the retaining clips/rings for the slip joint boot? These seem to be one use and I'll have to cut off the old ones.

A hose clamp would seem to be unbalanced. Other suggestions I've heard are to use a zip tie, but I'm not sure that will be secure enough (or apply enough even pressure around the boot seal).

Can I just go to my local Autozone and get the bands?
Is the regreasing of the splines pretty straight forward?

Thanks.