4L60E creep along speed

JHZR2

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It’s AT month for me!

Got out my 98 S-10 ZR2 that sat all winter. Have driven it about 35 miles. It has around 70k on it, owned since new, and it has run Dex VI since around the time that Dex VI came out.

For one thing, it has firmer shifts than the 47RE in my Ram. I used to think the 4L60E was pretty smooth, but it’s definitely more perceivable than the 47RE... not harsh, not firm, not clunking or slamming, just more noticeable. I’m not sure if that’s pointing towards something else...

For whatever reason I don’t get any creep along forward or backwards anymore. Sitting, idling, remove the brakes, and it won’t roll forward in D, or backwards in R. Once a tiny bit of throttle is applied it will roll along, and it drives and shifts fine (note I feel like the shifts are slightly more noticeable). No clunks, no noises, just thst tiny bit of throttle is all it takes to get it to creep along, albeit slowly.

The other thing I noticed is thst when driving along slow, like in a parking lot, if you coast down for a few seconds, and then hit the throttle, it can sort of clunk, like it catches harder a split second after giving throttle. But it runs fine any other condition. Not sure what that means though in terms of operations.

I have no reason to believe there is anything intrinsically wrong with the AT, it is fairly low mileage, has seen a relatively easy life, and this seems to have been induced by sitting... but putting 35 miles of varied use hasnt helped (yet).

Haven’t dug in much yet, but curious if there are any obvious things that I should be looking for?

The only other issue I’ve had in recent years is the front axle actuator (vacuum), causing a slight grind if the vac reservoir got too low. Not happening currently, driving in 2wd on streets, all seems ok. Truck starts and runs beautifully, catching on the first cylinder, first crank afte sitting for months.

Havent checked fluid level full hot yet, but seems OK...

No indication of seized caliper or parking brake.

What could be the issue?
 
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FWIW my 2005 Chevy Avalanche has a hill hold feature that engages when on an incline with my foot off the brake, and releases with a touch of the throttle whether In forward or reverse. I didn’t even know it had this feature for years. I don’t know if your 98 Zr2 has it or not but my 05 does. I haven’t noticed if mine does it on level ground but I’ll try it and see what happens.
 
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I'd jack up each of the wheels and see how they move by hand. I think that after sitting, you just have to get the rotors smoothed out again. Or just drive it a bit and see if things free up.
 

JHZR2

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FWIW my 2005 Chevy Avalanche has a hill hold feature that engages when on an incline with my foot off the brake, and releases with a touch of the throttle whether In forward or reverse. I didn’t even know it had this feature for years. I don’t know if your 98 Zr2 has it or not but my 05 does. I haven’t noticed if mine does it on level ground but I’ll try it and see what happens.
Not on my 98... used to roll faster.
 
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Check tire pressures. Confirm not stuck in 4x4 mode by turning tightly on pavement.
 
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Idle air control valve dirty? Idle a bit low due to fuel pressure or in need of a tune-up?

I remember years and years ago, I changed the fuel filter on a friend's 1990 S-10 4.3 at around 60,000 miles (mud poured out the inlet when I disconnected it) and the truck idled a little higher, and ran much better afterward. Surprised his fuel pump didn't kick the bucket from all the crud in that filter.
 
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its the Fluid? dex 6 is designed as more slippery if you will which is why you no longer get any creep at a standstill... sounds like you would be happier if you could change it out to the older style
 

JHZR2

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its the Fluid? dex 6 is designed as more slippery if you will which is why you no longer get any creep at a standstill... sounds like you would be happier if you could change it out to the older style
I’ve had the same Dex VI in there for years.


Idle air control valve dirty? Idle a bit low due to fuel pressure or in need of a tune-up?

I remember years and years ago, I changed the fuel filter on a friend's 1990 S-10 4.3 at around 60,000 miles (mud poured out the inlet when I disconnected it) and the truck idled a little higher, and ran much better afterward. Surprised his fuel pump didn't kick the bucket from all the crud in that filter.

Could be old/bad fuel. But it’s not idling any different (it always has been a little bit low). There may be a slight vacuum leak from the 4x4 system, fwiw.
Torque converter going bad.
Wasn’t bad when I parked it. How could sitting make it go bad?
Check tire pressures. Confirm not stuck in 4x4 mode by turning tightly on pavement.

It’s not stuck. Tires good (brand new BFG A/T KO2).


I'd jack up each of the wheels and see how they move by hand. I think that after sitting, you just have to get the rotors smoothed out again. Or just drive it a bit and see if things free up.
rotors are smooth and not too rusty or anything. No signs of calipers being stuck or parking brake being stuck.
 
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Put into neutral and push by hand? I wonder if a carrier bearing in the driveshaft is bad. Or toe went bad. Something to make lots of rolling resistance. Brakes are the obvious first spot to look but you did that already. Maybe take a longer drive, long enough to heat things up.

Otherwise I wonder if the pump is keeping the convertor full and/or keeping line pressure high enough. Slightly higher rpm gets pressure high enough to engage whatever needs to be engaged. Clogged filter? Just guessing here.
 

JHZR2

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Put into neutral and push by hand? I wonder if a carrier bearing in the driveshaft is bad. Or toe went bad. Something to make lots of rolling resistance. Brakes are the obvious first spot to look but you did that already. Maybe take a longer drive, long enough to heat things up.

Otherwise I wonder if the pump is keeping the convertor full and/or keeping line pressure high enough. Slightly higher rpm gets pressure high enough to engage whatever needs to be engaged. Clogged filter? Just guessing here.

Brakes are, I have to wonder if perhaps a bad hose that bleeds back by the time I check it?

I think the potential of a bad filter past it’s prime might be something.
 

Astro14

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First, check the fluid level. Always the first thing to do with transmission diagnosis.

Next, check the rolling resistance. If you’re dragging a brake, it could be rear drum adjusters, or it could be a bad hose. They fail internally, and then restrict the fluid return, resulting in brake drag.

And yeah, fix the idle.
 
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FWIW my 2005 Chevy Avalanche has a hill hold feature that engages when on an incline with my foot off the brake, and releases with a touch of the throttle whether In forward or reverse. I didn’t even know it had this feature for years
That’s not a feature of the 4L60e. Assuming you had the 5.3/4L60e and not the 8.1/4L80e.
 
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I like the idea of replacing the brake hoses. At this age they're probably due. Even the lower priced ones on Rockauto.com should be good.
 
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I'm also in the "Higher Rolling Resistance &/or Low Idle Speed" camp.

That being said.....I've seen some strange Forward Clutch issues cause similar symptoms before the Forward Clutch completely fails. Put the Shifter down in D1/L1....If it now rolls/creeps like it should....You have a Forward Clutch issue. D2 might work as well depending if this model has the 2nd gear start feature or not.
*D1 & D2 will bring on the Overrun Clutch which will augment pressure applied to the Forward Clutch.
*'96, '97, & '98 4L60E's used Allomatic sourced Forward Frictions which are notorious for premature wear, Allomatic redesigned them for '99 & they lasted okay. Then GM started using "Waffled" Borg Warner Forwards in '05 which are good to EOL & beyond.




"The other thing I noticed is that when driving along slow, like in a parking lot, if you coast down for a few seconds, and then hit the throttle, it can sort of clunk, like it catches harder a split second after giving throttle."

*Creeping along in with the Shifter in D4, Then letting off the throttle will overrun the Forward/Input Sprag, Then to accelerate the Input Drum/Input Shaft has to be brought back up to speed where the Sprag locks back up with the Input Sun Gear.....Normal operation for this unit.
 

JHZR2

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First, check the fluid level. Always the first thing to do with transmission diagnosis.

Next, check the rolling resistance. If you’re dragging a brake, it could be rear drum adjusters, or it could be a bad hose. They fail internally, and then restrict the fluid return, resulting in brake drag.

And yeah, fix the idle.

So, I’ve owned the truck since new. It’s always idled the same (550-650 depending upon ac, electric loads, temperature, etc.). Ive confirmed it to be correct/normal. So while low to me, it’s not something that can really be fixed, short of programming the ecu to command another value that wasn’t the OE setting.

Fluid, Pennzoil Dex VI is at a good level and looks good.

The truck is 4-wheel discs and aren’t dragging. But I didn’t mess around enough to see if it could be hoses or something related.

Im kind of figuring that since it’s over 20yo, the potential for a decomposed (?) part, bad filter, etc. is there. It is maintained, so it’s not like bad fluid, or something burned up. Very low use the last few years is my bigger concern than a broken part.

I'm also in the "Higher Rolling Resistance &/or Low Idle Speed" camp.

That being said.....I've seen some strange Forward Clutch issues cause similar symptoms before the Forward Clutch completely fails. Put the Shifter down in D1/L1....If it now rolls/creeps like it should....You have a Forward Clutch issue. D2 might work as well depending if this model has the 2nd gear start feature or not.
*D1 & D2 will bring on the Overrun Clutch which will augment pressure applied to the Forward Clutch.
*'96, '97, & '98 4L60E's used Allomatic sourced Forward Frictions which are notorious for premature wear, Allomatic redesigned them for '99 & they lasted okay. Then GM started using "Waffled" Borg Warner Forwards in '05 which are good to EOL & beyond.

Per above, idle is correct for this truck/engine, even if low to me... rolling resistance, sure, but what and why...

Sure hope it’s not the AT. Can a clutch assembly “dry out” from sitting too long/too much? I assume everything is bathed in fluid, but when not operated enough, maybe the fluid eventually falls away or evaporates, or gums up?

Thanks for the hint, I’ll, try the L test...

"The other thing I noticed is that when driving along slow, like in a parking lot, if you coast down for a few seconds, and then hit the throttle, it can sort of clunk, like it catches harder a split second after giving throttle."

*Creeping along in with the Shifter in D4, Then letting off the throttle will overrun the Forward/Input Sprag, Then to accelerate the Input Drum/Input Shaft has to be brought back up to speed where the Sprag locks back up with the Input Sun Gear.....Normal operation for this unit.

I agree, to a point. It has always sort of “caught” when doing that (rolling stops, speed bumps, stuff like that tend to be the conditions), but it was much more pronounced like a firmer/louder version of what it has historically done. So I’m assuming it’s a harder/harsher lock?

Thanks!
 
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My 05 4L60E has very little "creep" at idle on flat ground. Any kind of incline and it will just sit where it is. I'm not sure about the hill holding feature. I think I always keep my foot on the brake expecting it would roll back.
My 80s 2004R in comparison wants to move forward even on a hill. I figured it was differences in stall speed plus slightly higher idle on the Oldsmobile.
 
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