Idle while in gear question.

[willroach8908]

Folks,

I have a question(s) regarding idling under load. I currently work in metro Detroit so my commute to and from work can be bumper to bumper. On my way to work yesterday my idle seemed fine in (P) and when in gear when I was stopped. Well on my way home when the traffic was heavy, I noticed that the idle was fine in park or neutral, but when I was in gear and stopped it was down to 600-650. This was causing the engine to lope really bad; to the point I had to put the transmission in (N) in order to bring the RPM’s up and prevent what seemed like a stall out. Once I was moving again, it would shudder during the initial acceleration and then it seemed to run fine. The only difference I can tell between yesterday and other days is the air temp was warmer than normal. All seemed fine this morning when I came into work. Anyone have an idea what could be the cause of this?



Normal

In park 750 rpm

In gear 700 rpm



Yesterday afternoon in 45 minutes of bumper to bumper traffic

Air temp 80 degrees

In park 750

In gear 600-650



Any help would be appreciated.



Will

1989 W350 5. 9, 155K

2008 2500 6. 7, 95K

 

[cerberusiam]

Sounds like what happened to mine, TQ converter internals took a dump. When it starts pulling the engine down all the time its done.



Could have been other things like fuel or heat soak but that would be unusual. If it starts doing it more and more often it is likely the TC.

 

[Berrigan]

MY 2 cents. if idle speed is ok when cold and drops when ambient temp is warm its normal. My first gen and second gen tucks both did the same thing. One was an auto the other a 5 speed stick. My take is the problem is actually fuel temperature. After long freeway trips under load in high temps my idle would drop 200 rpm. I would bump up your idle speed a little and see if your acceleration stumble goes away.

 

[JLEONARD]

My first gen was almost opposite. It was a little slow (50 rpm or so) when cold and faster when warm. I attributed that to cylinder temps not burning all the fuel when cold, and complete combustion when warm.

My brand new 6 bta that I installed in a boat acted the same way, 50 ish rpm slower when cold. In the boat, the marine transmission would rattle a little as it was unloading the damper plate when the engine was cold. That is normal.

 

[cerberusiam]

Every one I have is the same way, idle is lower cold and higher warm. The only time I have an idle drop warm after working it hard meant it was pump rebuild time.



Dropping the trans into drive and loosing 150-200 rpms while neutral\park is pretty indicative of a TC problem. Same with the shudder on take off and likely quicker than normal shifting. A no stall TC will make a lot of things change drastically.

 

[willroach8908]

Thanks for all the replies. I would like to try and avoid throwing parts at it until i find the issue. so is there a definitive test that would tell me the Torque converter is going?

 

[JHumphries]

Stall Speed Test?

 

[cerberusiam]

so is there a definitive test that would tell me the Torque converter is going?

No mecahnical or electrical test you can run to definitely say it is the TC. You just have to know the symptoms and what a good TC feels like when it goes into gear, stalls when you hit the go pedal, and where the transmission normally shifts.



Pulling the idle down way below wher eit normally is in reverse and forward gears when stopped is one symptom. When you go to take off the truck feels slow and doggy or shuidders, that is another symptom. Usually when the TC is in a no stall mode you will get quick 1-2 and 2-3 shifts, quicker than they normally would be with the associated throttle position. Once it is up to speed and you don't drop under 25-30 mph it all feels good.



There is a possibility a TV cable setting too loose will cause some of these symptoms but never the bogging idle in gear. Check your TV cable setting to make sure it is conected and working correctly then see what it feels like.



FYI, if the sprag is just on the verge of failing in the TC, you will get the bog and weird shifting warm but not cold a lot of times. However, once it starts having these symptoms its just a matter of time until the sprag freewheels all the time, then its ots only a matter of time until locks solid and you have no more go.

 

[HHhuntitall]

Just another thought... . Did you have the AC on while in route home? If your compressor is dragging or building unusual head pressure, it can pull the engine idle down. I thought maybe you didn't have it on on the ride in, but did on the ride home.....

 

[willroach8908]

AC was not on when all of this was happing. I went throught the fuel system, tightend some loose lines, changed the fuel filter, this didnt seemed to help any. I think I will change the TQ the first opportunity I can. Thanks everyone for the help!

 

[HHhuntitall]

Yep. Just thought I'd ask. I had an '05 come in that puked the TC, and it would idle itself up until it would just take off..... Similar happened on it. FWIW, Cerebrusiam called it, too.....

 

[DVolk]

A reminder If your defrost is on your ac compressor runs !!!!!!!!!!

 

[willroach8908]

Well I ran some Lucas transmission stuff through it today, took her for a ride, and it seemed to help at first. Once trans was good and warmed up it went back to acting up. Was told by a local trans guy that that stuff would work and buy me some time until i could afford a new TC, guess not. Can any one recommend a solid OEM replacement torque converter? Im just looking for a affordable replacement that will last on a stock truck. Any suggestion are appreciated!

Will
1989 W350 5. 9, 155K
2008 2500 6. 7, 95K

 

[cerberusiam]

Where are you located? Any transmission shops close?



Go here PATC 46RE 47RE 48RE Transmissions, Performance Transmission A518, 518 and search the page for #NLUD.



Hughes also makes a non lockup TC you can get thru Summit racing.



Most of the places do NOT have these 518 cores anymore. The last 2 I had done we had to send on our TC and have it rebuilt due to lack of cores.

 

[cerberusiam]

Yep. Just thought I'd ask. I had an '05 come in that puked the TC, and it would idle itself up until it would just take off... .

Yeah, its much worse on the CR's when this happens, and it does frequently. The ECU just keeps trying to hit idle by adding fuel and no way to recognize ther eis an issue.



It will run the rpm's right to 2100, the defuel point with less than 5 mph wheel speed, while you stand on the brakes to hold it. :-laf Shift it to neutral and it bounces off the rev limiter then idles down.



People think your trying to race them at a stop light. :-laf

 

[HHhuntitall]

Where are you located? Any transmission shops close?



Go here PATC 46RE 47RE 48RE Transmissions, Performance Transmission A518, 518 and search the page for #NLUD.



Hughes also makes a non lockup TC you can get thru Summit racing.



Most of the places do NOT have these 518 cores anymore. The last 2 I had done we had to send on our TC and have it rebuilt due to lack of cores.

That's what I had to do on a 91 I got in. I sent it to Blumenthal's and they rebuilt it, and it was wayyyy tighter than any stock convertor I'd ever driven in that year model, despite no lock up. Really helped the fuel mileage.....



Have you used any of the Hughes TCs in any of your stuff?

 

[cerberusiam]

I have not tried the Highes offering. Always was a little leary it might be just a good stock rebuild with not enough TQ multiplication changes to be worth the money.



I had 2 of them from High Torque in Idaho, one we sent back to them to be rebuilt because it would not hold the power. Typical when you turn the wick up.



The other went south like the OP described and had it rebuilt at Transmission Parts Unlimited here in Atlanta. That work really well so far and made a noticeable difference on stall, power transfer, and rpms at speed.

 

[willroach8908]

Well I took it to a local diesel performance shop (very reliable), to rule out any fuel system issues. They were able to isolate the issue to the injection pump :{. They said they pulled a return line that houses a screen and found lots of brass and metal shavings in it and that these are signs of issues going on with the pump. They quoted me a price range for rebuilding that pump and that range was dependent on the components out of spec, worn and needed replaced. Are pumps that have been rebuilt as reliable as a new pump? Any suggestion and help is appreciated.



Will

1989 W350

2008 2500

 

[cerberusiam]

Are pumps that have been rebuilt as reliable as a new pump? Any suggestion and help is appreciated.

That is totally dependent on the builder and how meticulous they are. That varies so much from person to person and vendor to vendor its hard to comprehend.



A lot will also depend on how many parts they replace. There are updated rollers, springs, etc, that can make it a better pump. The hydraulic head and clearances is also pretty important and a lot of times that doesn't get checked and set correctly.



The aftermarket hydraulic heads are $300 or so while the Bosch head is $900 plus and a special order. The Bosch head is much better obviously but the cost and time to get is prohibitive.



You cannot get a new pump anymore so the question really is moot, a remanned pump is all that is available as a unit or rebuilding the one you have.



As a rule, a rebuilt is not going to be as reliable as new but that is relative to how many miles you drive and how you maintain the fuel.

 

[Paychk]

I would suggest looking for a re-builder that is authorized by Bosch and a member of ADS, try looking here:

Association of Diesel Specialists | Find Reputable Diesel Service