Engine/Transmission (1994 - 1998) Idle speed, road speed at idle, etc

[CharlieFoxtrot]

Hey y'all--



My truck has mild mods (see sig), including a DTT trans and low-stall torque convertor.



It idles a hair over 500 RPM in drive, while I think the spec is 600, iirc. Idle in neutral is about 850. According to the factory tach, fwiw. .



I don't really want to speed up the idle to the specified speed, both because it already is jerky enough when shifting into gear from park, and because if I take my foot off the brake, the truck will gradually accelerate to ~30 MPH all by itself. The other day, I pulled a dead F250 through a field and into a gas station while touching only the brake pedal!



Is this normal?



thanks

kevin

 

[Missouri Mule]

On the auto trans it should be 750 to 800 rpm in drive with a/c on.

Make sure your tach is working correctly. ( There is some type of remote tach you can use, sorry can't remember the name of it).



There is built in lug protection (known as lugging) in the governor of the p7100 pump (I think). On my Mule(96 5spd) if I take my foot off the go pedal in the lower gears the idle/tach will drop down below 600/780 rpm then something kicks in and it will go to 780 (or higher). I can shift thru the gears while it is in lug protection. 1 rst gear will run at 5 mph, 2nd 10 mph, 3rd 15 mph, 4th 20 mph, haven't tested it in 5th ( this is with my foot off the go pedal, it will even keep going with my foot on the brake in 1rst gear).



(Lugging is when you are running to low rpm for a certain gear, this will ruin your engine. )

 

[HBarlow]

Hey y'all--

My truck has mild mods (see sig), including a DTT trans and low-stall torque convertor.

It idles a hair over 500 RPM in drive, while I think the spec is 600, iirc. Idle in neutral is about 850. According to the factory tach, fwiw. .

I don't really want to speed up the idle to the specified speed, both because it already is jerky enough when shifting into gear from park, and because if I take my foot off the brake, the truck will gradually accelerate to ~30 MPH all by itself. The other day, I pulled a dead F250 through a field and into a gas station while touching only the brake pedal!

Is this normal?

thanks
kevin

Yes, its probably normal because of the built DTT transmission and very tight torque converter. That's one of the compromises you make when you build the automatic to handle high torque and heavy loads.

Your transmission is trying to launch the truck at idle.

I have never owned a 12 valve but had a full DTT transmission in an '06 48RE and it was similar to what you described.

 

[budnate]

pretty sure its your converter... . I just rebuilt my trans and now my truck with a Goerend converter is doing the same to me, a decent load on it when stopped at a light, if you let off the brake it will start rolling pretty good, I have not tested how fast if i just let it go... this is my first triple disc converter,



my truck likes to idle at 675 in neutral and is a pretty good hit when slipping into gear at that... love everything else about the products but kinda unhappy on how much load is on it in gear, I have another converter on the way from them to lower my final rpms in O/D a tad, I hope this goes away with the next converter.



B.

 

[CharlieFoxtrot]

Thanks guys! I love the trans & convertor, so I'll leave the idle alone.



Bud, if your convertor is locked in OD, how will a different convertor change the RPM?



Bill, that might be a manual-trans-only thing. I don't think an automatic could ever drop below the idle speed setting.

 

[budnate]

final stall speed when locked up can be adjusted during the build of the converter... every motor is a tad different... before the build i was in the sweet spot at at about 1850 1900 running 70-72 down the road, with the new conv i am running a strong 2000 same speed... a tad to much for my taste, he built one a little different from the one he shipped me the first time, it should nail my target rpm the way I was before the build..... beyond that I dont know... not a converter wizard just know it was off a tad and they are totally taking care of me no hassle... cant say enough good things about Goerend. nice old school care from the first call all the way through and follow up with their products.

B.

 

[Bob4x4]

final stall speed when locked up can be adjusted during the build of the converter... every motor is a tad different... before the build i was in the sweet spot at at about 1850 1900 running 70-72 down the road, with the new conv i am running a strong 2000 same speed... a tad to much for my taste, he built one a little different from the one he shipped me the first time, it should nail my target rpm the way I was before the build..... beyond that I dont know... not a converter wizard just know it was off a tad and they are totally taking care of me no hassle... cant say enough good things about Goerend. nice old school care from the first call all the way through and follow up with their products.



B.

The engine rpm with the convertor clutch locked up can not be changed..... the stall speed can and with programming the lock up point can be changed

 

[cerberusiam]

final stall speed when locked up can be adjusted during the build of the converter... every motor is a tad different... before the build i was in the sweet spot at at about 1850 1900 running 70-72 down the road, with the new conv i am running a strong 2000 same speed

In short, no. Don't know what you got going on there but there is no adjustment to rpm in lockup. It is 1:1 input shaft to engine rpm when the clutch engages correctly.



Sounds like your TC is simply not locking up correctly.

 

[budnate]

I will report back later if it really does change... converter should be here and going to swap this weekend hopefully..... I dont build them, I called and said I was off a tad he said no problem, he said my RPMs will go down rolling down the road locked up like it was before that is all I know,



I fully understand 1 to 1 locked up, I am sure if my rpms could'nt be changed he would'nt say it could.



B.

 

[Bob4x4]

Have him explain how a locked up torque convertor can change gear ratio ???

 

[budnate]

here you go Bob,



Chrysler Turbo Encabulator - YouTube

 

[Bob4x4]

here you go Bob,



Chrysler Turbo Encabulator - YouTube

:-laf That has been shown a few times by instructers

 

[dieselmechanic101084]

a friend of mine has a 12 valve that idles at about 450 rpm cold and as it warms up idle gets faster. The p 7100 is a reman. He also says that when he stops it will sometimes stall or when he turns the wheels it will stall. He has to keep foot on throttle to keep running.

 

[hsmith]

No brainer here. Bump the idle up, if auto, to 750 in gear with ac on.

 

[HerbW]

I have the same problem with my 98 12 valver with a billet low stall torque converter. If I set the rpms up to spec, I seem to ride my brakes in town to slow it down once warm. I hate the cold engine when doing trailer hook ups etc because I stall alot due to low rpms. Once warm, the low rpm works great as it idles faster then.



Has anybody installed a manual throttle control cable and dash knob? I could up the rpm when cold and release it later when warm.



Thanks for any help. Herb