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Discussion Starter #1
I've been trying to narrow this problem down for awhile and wanted to see if maybe someone here had any ideas.

If I take my foot off the gas and let the truck slow down on it's own I notice the rpm's will kinda fall gradually until it gets to a point around 1500 rpm's where it seems like the torque converter let's go and it falls to idle speed (or close to it).

If I give it gas again at this point the rpm's will climb quickly (almost like it's in neutral) before hitting 1200-1500 when I will feel a "stutter". The rpm's drop and the truck begins accelerating. This feels very similar to the torque converter locking up in 5th gear.

It's not 100% repeatable, although I wouldn't say it's rare either.

Accelerating from a dead stop is smooth. I don't feel any slippage under heavy acceleration.

Is this normal?
 

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When letting off the throttle then as you slow down the converter kicks out then you coast, YES this is normal.
When you quickly accelerate at this point having a slight delay this is also normal.

Diesels are not exactly like a gasser, the turbo needs to spool up before it gitty-up and goes, depending on the rpms and speed it might instantly take off or delay.

Having good intake airflow and good clean airfilter will make a difference.
 

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Discussion Starter #3
So it's normal when after the torque converter disengages while coasting to a stop to take a bit of RPM for it to hook back up?

I'm not talking about spool up or anything like that. It's more like driving a stick and letting the clutch out late and fast. Let me play out the scenario where it happens the most.

Coasting up to a red light, foot totally off the gas. The speed falls and the RPM's with it, around 1200 RPM the torque converter let's go and the truck falls down to idle of around 720 rpm. The truck is still rolling at this point at 15-20 mph. The light changes to green, so I place my foot back on the gas (note: this is not a quick acceleration, just trying to get back up to 35-40 mph speed limit and getting there leisurely). I rest my foot on the gas and the RPM's climb quickly up to 1200ish. Then it "catches" (like dropping the clutch in a manual) with a noticeable (although not audible) thunk. It feels like a very firm shift. The RPMs fall to the appropriate number for the speed the truck is traveling at and then it drives perfectly normal.
 

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When you’ve let off the throttle driving while it’s coasting you usually feel the trans converter kick out and the rpms drop a little.
When you immediately accelerate there can be a slight delay, that’s where there can be the turbo spool up delay depending on speed, rpms, intake airflow with more airflow you’ll have quicker spool-up or sometimes just because.
Have you engaged towhaul while driving around not towing to see how it shifts?
How many miles is on your trans?
When was the last time your trans was serviced?
Have you changed the spin-off filter, it’s suppose to be changed about every 10k.
How does the fluid look?
Where is the fluid level on your dip stick?
 

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Discussion Starter #5
The delay is 100% engagement and not boost related. It feels solid like a shift as opposed to the surge that a turbo brings.

When it happens it is under very slight acceleration and where the turbo would only see a couple pounds of boost anyways. Air filter is new in the last 2000 miles. Boost level are where they should be I believe, I run an idaho rob EFI live tune at +90hp and see peak (sustained) boost around 28-30 psi read on an edge insight 2.

I've never experienced the problem while in tow haul mode.

around 190k on motor/trans. Last fluid change was at 160k miles, I put on a new spin on filter every time I change the oil. Fluid looks good, smooth between the fingers without being watery or gritty. No burning smell. I've done both hot and cold checks and the fluid level falls in the correct range on the dipstick for either.

Otherwise the truck performs excellently. There are zero other problems with shifting, accelerating, or boost.
 

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Otherwise the truck performs excellently. There are zero other problems with shifting, accelerating, or boost.
Then I don’t understand your concerns.
Maybe take it somewhere to have it checked out if this concerns you.

So far it’s taken 3 posts for you to mention that your running a 90 hp tune on a stock trans.
There are no tunes on this planet that are trans safe.
You’ve explained a lot in your first 2 posts but left out the important stuff.

What’s your opinion on where the proper trans fluid level is suppose to be.
What color is the fluid ?

One thing I would check out a little more is your low boost, I’m running ATP heavy towtune 30-40 hp my boost is 31-32.
But that really should not affect shifting with still in the 28-30 range.
My whimpyest tune 25 hp will maintain 29.
 

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Have you considered putting your smallest HP tune in and drive for a long while to see what happens ?
Bigger tunes have a effect with the trans to perform like what your expecting and shortens the trans life much quicker than you’d like.
 

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Discussion Starter #8 (Edited)
I spoke with a local trans shop and while they told me what I was experiencing was not "normal" they did say that because of the frequency of it happening, the fact the trans had not thrown any codes, and because the trans had never limped it would be almost impossible to diagnose. It could be a loose wire, a sticking solenoid, or another half a dozen issues. Their suggestion was to wait until the problem was bad enough I could replicate it for them, or wait until I limped the trans.


Regarding the trans fluid levels, when checked they are in the high areas of the crosshatching on the trans dipstick annotated as "hot" and "cold" with the level appropriate for the temp of the transmission. Fluid checks are done on a level surface, and after shifting the trans through R D and finally P. Trans fluid is pinkish with a little bit of gold, probably close to time for a drain and fill.

Regarding the boost. I'm not surprised my reported levels are a little low, I also don't drive the truck very aggressively (it is an almost 4 ton vehicle after all). I've never done a 4wd launch, heck I've never done a proper 2wd launch under boost. Never even done a burnout or a donut. The boost levels I quoted are under heavy acceleration while passing for example. I'm sure my turbo it a bit worn after almost 200,000 miles and I expect to have to put a new one in sometime in the next 30k-50k. I've tested the system for leaks, and recently replaced the air filter. If you can describe a method for checking boost levels that would not involve me breaking laws excessively on city streets or putting excessive strain on the trans I can try and do it. I checked my edge insight and it's highest record boost value was 36lbs, although that has probably not been reset for over a year though. I reset it and I'll try and take the truck out tonight and see where I end up.

I apologize for not mentioning the tune, you are correct that is a very important bit of information that I left out. I could have sworn that I had added it to my sig when I was more active on these forums. I am well aware that no tune is "trans safe" and I am fully aware that the stock allison 6 speed is a bit of a weak link in the driveline. Since I am aware of that, I do my best to drive accordingly. I purchased tunes from Idaho Rob specifically because I was told his defueling between shifts was easier on the trans than other tunes. I drive my truck the way I imagine old people drive sports cars. Leisurely driving around 90% of the time with the other 10% being 3rd/4th gear roll on's on highway on ramps or occasional "brisk" starts from stop lights (with traction control on).

Regarding the different tunes. My available tunes are +0 HP towing, +40 hp towing, +90 hp economy, +120 hp "race" (never used), and Valet.
 

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Proper fluid level is just above the low hot hash mark.
Search and you’ll find.
I’ve found right in the middle of the low - high hot hash mark works best for me trans temp 170-180.
If your level is on the high side it’d be best if you lower to at least the middle of the hot low - high.
A simple spin-on change will remove about 8 ounces.

I doubt the higher fluid level is causing what your experiencing.

I still suggest to run a lower hp tune, me personally I’d never run above 50 hp.

I run my ATP heavy towtune 24/7-365, I load one tune at a time.
I have 4 different EFILive tuners with multiple tunes from all 4, all are single loading one at a time.
I found one single tune I like, and it stays.
No chance of dumb mistakes switching on the fly.
 

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Discussion Starter #10
Proper fluid level is just above the low hot hash mark.
Search and you’ll find.
I’ve found right in the middle of the low - high hot hash mark works best for me trans temp 170-180.
If your level is on the high side it’d be best if you lower to at least the middle of the hot low - high.
A simple spin-on change will remove about 8 ounces.

I doubt the higher fluid level is causing what your experiencing.

I still suggest to run a lower hp tune, me personally I’d never run above 50 hp.

I run my ATP heavy towtune 24/7-365, I load one tune at a time.
I have 4 different EFILive tuners with multiple tunes from all 4, all are single loading one at a time.
I found one single tune I like, and it stays.
No chance of dumb mistakes switching on the fly.
thanks for the advice, I'll go ahead and do a drain and fill (since it's due anyways) and toss on a new filter. I'll try and even out the levels when I do the drain and fill. :thumbsup
 

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Let me ask, was the trans shop you spoke with a Allison savy??? Your 2009 is a 6spd so take this with a grain of salt, but my 2004.5 LLY 5spd does exactly the same thing you describe, Did before I had the trans built, and does after. There was nothing wrong with my trans when I had it built, just 200k miles and I wanted it to hold up to the tune options. I guess what that is saying I agree with Dan,, its acting perfectly normal IMPO

Do this, set Tow/Haul and it should stay locked all the way to 1st gear (I believe). That should ease your mind that nothing is wrong. Now that I think about it,, my old tired 5.3 4L60 does exactly the same. Freewheels below lockup RPM, and tends to 'flash' a little if the light turns green and I get back in the throttle.
 

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Discussion Starter #12
I've got a bad habit of trying to find problems when everything is actually running well. I'm gonna do my best to totally forget about it unless it starts popping up more often or starts throwing codes.
 

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In towhaul the converter locks after the trans shifts into 2nd gear and stays locked thru all of the gears.
I really feel if your using your 90 hp tune and doing what your explaining, letting off until the convert unlocks then getting on it the longer than maybe normal delay, your trans is slowly going on its way out, even with trans safe tuning.
If anyone would read the fine print on trans safe tuning, you'd read that they are covering their behinds when stating
"Safe trans tuning" at least up until you drive like a fool" (my words).
It doesn't take much jumping on it before you eventually toast it.

Be smart now that your concerned at least go to your 40hp tune, but that's your choice.
If you had a standard 40 hp tune and a 40 hp towtune you would not notice any differences with performance or mileage.
 

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Discussion Starter #14
So I went out tonight and did a couple full throttle runs to about 80 mph.

Peak boost around 32 psi with sustained bouncing between 28-30 psi. I'm going to drop it off at the shop next week and have them run a leak test (I would do it myself but I don't have an air compressor currently and I'd rather not try and do it with a bike pump).

Hopefully I just have a small leak somewhere (here is to praying a boot is on its way out) and the turbo does not need a rebuild.
 

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Did you do a PCV re-route ?
If not, do you have oil seeping out around the clamps collecting dirt/dust from the turbo to intercooler hose, make sure the clamps are tight.
Maybe even remove the pretty blue hose clean it up including the pipe then re-install.
Turbo to intercooler tube boot/tube at the intercooler is oil seeping around the clamps ?
You also have O-rings from the intercooler out thru the cold side pipe/elbows 2 O-rings.

I feel if you had a boost leak it'd be much lower than what your showing.
Elements, temps the slightest changes will affect the boost.
Now if your on a flat drag strip pedal to the metal, max boost should be max boost.
If you have the EDGE CS/CTS in records, it'll keep your max numbers on several pids including boost, until you clear them, then it starts all over.
 

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Discussion Starter #16
Did you do a PCV re-route ?
If not, do you have oil seeping out around the clamps collecting dirt/dust from the turbo to intercooler hose, make sure the clamps are tight.
Maybe even remove the pretty blue hose clean it up including the pipe then re-install.
Turbo to intercooler tube boot/tube at the intercooler is oil seeping around the clamps ?
You also have O-rings from the intercooler out thru the cold side pipe/elbows 2 O-rings.

I feel if you had a boost leak it'd be much lower than what your showing.
Elements, temps the slightest changes will affect the boost.
Now if your on a flat drag strip pedal to the metal, max boost should be max boost.
If you have the EDGE CS/CTS in records, it'll keep your max numbers on several pids including boost, until you clear them, then it starts all over.
I think you nailed it. The hot side pipe has noticeable oil where it connects to the intercooler. I'll disassemble clean and reassemble.
 

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I think you nailed it. The hot side pipe has noticeable oil where it connects to the intercooler. I'll disassemble clean and reassemble.
That's the one that usually blows off at the best 'uhNo time while your towing up a steep grade at max boost.
Hell, I've even had them blow off when not towing at max boost up a steep grade.
This is the reason I suggest doing it, just don't go cheap with hardware crap.

Check the hose out if its soft, you might consider replacing it, or at least buy one and have for a spare.

That's one thing that usually leads some people to do the PCV Re-Route, no more oil screwing things up in its way.

There's a few that don't agree, they're still stuck in the 50's -60's
when lots of blow-by was the diesel thing with big rigs.

Mines been on since 2008, I still don't have any drops on my concrete driveway.
I extended my re-route hoses (2) to the rear of my cab using 1" ID X 8' long pvc.
 

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Discussion Starter #18
So I got it all cleaned up and put back together. The hose had worked it's way off a good bit. You said it's supposed to be pretty firm and not very pliable? If that is the case I should order a new one for sure, it was about as soft as a radiator hose. How tight is that hose supposed to be torqued down to. I collapsed the spring but I didn't want to torque it real hard and risk damaging the already weak boot.

There was no accumulation of oil inside the piping, although I can totally see why a PCV reroute is a must. Would you recommend buying a kit for the reroute or just buying some decent hose and making one myself with a catch can.

BTW @D_R_C I really appreciate you taking the time to answer my post.
 

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On the hose squeeze the rubber thickness roughly 1/4' to see if its soft squishy, if its not then your probably ok.
After they blow off and put back on a couple of times, they are trash.
Having a back up spare is a good idea, IMO.

On do a re-route, buy the kit don't use hardware crap, you'll need a rubber cap to plug off the opening going into the turbo, you don't want to use rubber caps from any hardware/plumbing store.
My saying is do it right the first time, buy a kit made for this, I've made mistakes using hardware crap for engine compartment areas, luckily I caught in time and replaced with rubber made for this before something bad happened.

I went with the deluxe kit in 2008, in my signature.
https://dirtyhookerdiesel.com/c-426611-pcv-re-route-kits.html

Click on my D_R_C, then click on public profile, then click on albums you'll see a few pictures.
 

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If you'll feel better attach a can or open container under the outlet on each side, that'll work if your concerned on possible oil drops.

Your welcome,
Hopefully I was able to direct you somewhere with good results other than over a cliff. :thumb
 
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