Engine/Transmission (1994 - 1998) Need to lower power band

[gbrinlee]

Well after a few hours of searching through the forums, I feel a little better informed. Yesterday I took my 97 to a local diesel shop too have the timing set due to poor low end power. They set the timing at 16 and told me that the reason the truck had poor power from a stop was that it appeared to have a "low stall (told around 1300) convertor. " I was told that my only options were to either replace the convertor with a higher stall unit or to add more fuel.



What is the proper way to get power down low? Truck will be driven unloaded most of the time, however it is used as a backup rig for our horse trailer. Diesel shop told me that it would probably get stuck if it had to stop on a steep hill with a trailer attached.



Truck is the 97 3500 4x4, #6 plate in the middle, what I believe to be stock injectors and turbo. MBRP 4" exhaust, missing cat, Goerend trans, stock height tires (it is a dually), 30 psi of fuel pressure, boosts to around 35 once moving. AFC full forward. The truck runs great once the boost builds in 2nd gear (no boost in 1st). I do have a call into Dave at Goerend and am awaiting his response also.



Appreciate any information. Also does anyone have a #4 or #5 plate lying around that they need to sell?

 

[Missouri Mule]

You should post your rear end numbers also.



Have you played around with your AFC Starwheel yet?

 

[fest3er]

Slide the plate forward until it starts to smoke at launch or until you have adequate low-end power, whichever comes first. Then adjust the AFC housing to remove the smoke. You might need to adjust the starwheel, plate and housing several times until it works right.

It sounds like your problem is that you don't have enough fueling to get the engine up to 1500-1600 RPM (past the TC) where it can start making boost. This is exactly what happened when I put the Purple TC in my stock '98. Truck was a complete dog until the engine could stay above 1500 RPM or so. Sliding the stock plate fully forward and tweaking the AFC housing to minimize the smoke cured that problem.

 

[WilsonF]

Just a question. I have always been told that in a diesel you wanted a low stall converter.
Is that true?

Floyd

 

[HBarlow]

Our Cummins engines produce at least 350 ft. lbs. of torque at idle and depending on engine year and tune 400 to 650 lbs. ft. of torque at 1500-1600 rpm all the way up to 2500 to 2900 rpm.

You don't need or want a loose torque convertor.

I am not a tuner so my opinion is not worth much but the modifications you've made are probably overfueling it before boost rises. Does it smoke at launch?

You are working against 3. 54 gears and the old 47RE transmission so it's simply not going to launch hard until you get it rolling a little.

 

[gbrinlee]

Oops, I did forget the gear ratio, they are 4. 10s. I had the plate full forwawrd, moved it back to the middle and the truck seemed to run better. Have moved the starwheel and have it at the point where there the spring is just at rest (no tension). No smoke at launch, just a light haze even when the plate was full forward. Once it starts building boost it takes off like it is on fire (still no great smoke display, just a little darker haze). Truck runs good just need more on the bottom, if you floor it from a stop it just starts rolling until it gets to 2nd and starts boosting.

 

[Missouri Mule]

It seems to me in the TDR mag that they stated a high stall convertor was better (IIRC).

 

[gbrinlee]

Missouri Mule I do not remember the article. I am using whatever convertor that Dave Goerend sent with the trans they built. Have been extremely happy with the transmission. I had a 96 2500 and sold it to purchase the 97 3500. I transferred my favorite parts from the 96 to the 97 (including the trans). The transmission functioned flawlessly in the 96, only starting having an issue after the transfer to the 97. I have fixed the low power problem and now am going to try a "test pull" with the trailer in the next few weeks. Thanks for the input.

 

[HBarlow]

It seems to me in the TDR mag that they stated a high stall convertor was better (IIRC).

I don't know what was recommended in TDR, you could be correct.

What I know is a high rpm stall convertor comes with a trade off. A high stall convertor allows the engine to rev to a higher rpm before it engages and launches the truck. It also means that during ordinary driving on city streets at speeds between start and torque convertor full lock-up the engine will alway rev as the TC slips. They are very annoying to drive.

Drag racers use high stall TCs to allow their radically-cammed gasoline V8s to rev to 3500 rpm or even to 6,000 rpm before engagement to allow the engine to get into their power bands for hard instantaneous launch. The loose TCs work great for drag race launch but are lousy as daily street driven cars.

 

[Missouri Mule]

gbrinlee, I'm sure Dave Goerend put the right torque convertor in for your needs and with a 4. 10 you should be able to eat hills for midnite snacks.

You probably need to look for plate that fuels at low rpms to mid rpms (towing plate). Are you sure the trans isn't acting up?



I'm re-reading the old issiues so I'm mite come across torque convertor suggestions. Been driving manuals for 11 years (except my Mom's car).

 

[Grumpy John 4x4]

power

Have you changed your overflow valve on your pump?

 

[gbrinlee]

The overflow valve has been changed. The power problem has been repaired, the the fuel lever was hitting underneath the cam plate. I found the repair on cumminsdatabase.com. I was going to do a "test pull" with the trailer, however my trans is back to its "dancing" again. Has anyone ever dealt with a transmission that seems to hunt for a gear? It has to be one of those odd electrical problems as it is not consistent. When it first started acting up I replaced the output speed sensor and that temporarily seemed to fix it. About a week later it started again, then I replaced the gov press solenoid and sensor. Good for about another week then yesterday back to the same problem. Were there any PCM problems like this? I just do not want to have to pay for a PCM and find out that it does not fix the truck either. What led me to replace the gov solenoid and sensor was that I installed a pressure gauge in the gov port on the trans, when driving the truck had to get to 30 mph before I got any pressure reading. At that speed the pressure would spike to 90psi then drop to 0 and go erratically all over the place. Does not the PCM control the pressure solenoid? Once I repaired the low power problem it made the truck fun to drive again (until the trans started acting up again). I do not believe that it is the transmission as it did not do this in my 96 that I swapped it from. No problems with the TPS. This happens in the 1-3 gears.

 

[gbrinlee]

Missouri mule, I believe that Dave provided me with the correct parts also. When I was shopping for a trans about three years ago I purchased from them on the reputation here on the TDR. I could have spent that money with anyone, I still believe that I made the correct choice in my purchase as the people there have been great. (although I do wonder if they get tired of all the questions from people that are not "trans" people). I have searched on here and not found a thread describing my transmission problem. It seems that most of the threads are about overdrive or TPS problems.

 

[HBarlow]

I haven't owned a 12 valve with 47RE or one with a Goerend rebuild but I'll assume all three are similar to the '06 w/full DTT rebuild I owned for two years.

James Northrum, who did my full DTT build, explained that some of the modifications that changed the shift points and torque converter in my 48RE would cause some irritating hunting back and forth between 1st and 2nd and nothing much could be done about it. I accepted it and figured that overall, the performance of the full-built DTT was so vastly improved over stock that I could live with that minor inconvenience.

Yours may be similar.

 

[BDaugherty]

I'm not a 12v guy, but isn't there a different spring available for the AFC that will allow you to fuel harder at lower boost levels while still controlling smoke?



PDR Diesel Performance: AFC Spring Kit

Something like this.



TST AFC Spring Kit

Or this.

 

[gbrinlee]

Harvey, thanks for your input. I guess that my description was not entirely accurate. The transmission is not actually hunting as much as it just shifts in and out of gear at random times. I am starting to lean more and more towards the PCM. I am going to hook up the gauge to the governor port again tomorrow and drive it around, see what happens. Since I put the new solenoid and sensor in I do not believe that they are the culprit. (the old ones were probably not bad, should have not thrown them out). Will let you know what I find tomorrow.

 

[gbrinlee]

BDaugherty, yes there is an AFC spring kit available and it has been installed on the truck for a long while. It allows more fine tuning of the smoke when there has been a cam plate installed.

 

[tp0d]

gbrinlee:

I bet you have a bad connection (ground or otherwise) somewhere that is causing this problem. (the gear hunting) I`ve solved a few weird problems by removing any connectors I can find, inspecting for corrosion, spraying both sides with RadioShack TV Tuner cleaner/lube, then replugging 2-3 times to scratch up the connections. I would start with the PCM, and all transmission plugs. Might want to try checking any accessible splices for corrosion also. .

good luck

-j

 

[gbrinlee]

tp0d, that is exactly where I am headed. I will have a Snap-on "brick" scanner tomorrow. Will hook it up and see if it can point me in the right direction. Am going to go through all of the connections also. Lots of fun. Thanks for the info.

 

[EBramwell]

Very interesting... . Ive got a 97 3500, auto, 3. 54 gears, with a lot of the same build as gbrinlee even a Goerend trans and I'm also having the same exact problem, no low end power.
I had my timing checked and then re-checked, moved the fuel plate all around, same with the AFC. Ended up with a 0 plate full forward and a gutted AFC.
Runs great unloaded and doesn't smoke hardly at all. Loaded with trailer still has no low end, I cant figure it out. Ive got lots of boost through out, and fuel pressure is at 30 psi... . I don't know. #@$%!