Rare1

Hi, everyone. I've been lurking on your forum since I bought my truck and thereby learned a lot. Now I have questions, specifically for Jughead, but anyone could jump in.

Jughead, when Granpaw asked about his transmission slipping earlier, you said to change the throttle pressure adjustment 3/16". This must be what my Haynes manual calls the Throttle Valve Cable. Three times now, I have felt my truck shudder a little when climbing a hill in overdrive lockup, 60 MPH @ 1700 RPM, boost 25+ PSI, cruise control. I thought it was the transmission slipping so I have avoided those conditions since, but I don't understand how it could slip when it's locked up.

My questions are: Is it slipping because the fluid pressure is too low at 1700 RPM? If I shorten the cable 3/16" will the pressure increase and stop the slipping? Will it change the shift points significantly? I like the way it shifts now.

You said no damage would occur but Haynes says the cable end must be exactly aligned with the attachmet stud or it "can lead to early transmission failure." Please comment.

If this is not a fix for me, ATS is just down the street in Wheat Ridge. I've been there to fix a "starting in 2nd" problem and they are good people.

I like this forum and the people on it. The opportunities for education are endless.

bigbaddiesel

Did they get your starting in 2nd problem figured out?

Rare1

Yes, ATS fixed the "starting in 2nd" problem, but that is not the full description. It did try to start in 2nd, but as soon as a little load and RPM were developed, it shifted down to 1st and went up through the gears normally as velocity increased. So my problem more precisely was "does not shift into 1st when coming to a stop." The cause of the problem was an orifice clogged by debris in the transmission fluid, and the source of the debris was, according to ATS, friction material scrubbed off of various surfaces. They changed out a solenoid valve (which contained the orifice?) and cured it. Also, changing out the fluid should have removed most of the debris.

I suppose the debris and shuddering at cruising speed are related. Since the transmission works good now I would like to eliminate the shudder, if adjusting the throttle valve cable will do it, as a short term fix. I know that eventually I will need an ATS transmission.

Rare1

Bigbaddiesel, I see that your HP is nominal, torque is way up, and milage is poor. Yet you don't list any engine mods. To what do you attribute the abnormal numbers? Tires, heavy foot, plate position, ?

Do you believe your 600+ ft-lbs of torque is "factory" for your engine and the spec 400+/- is not always true? Is your engine turning about 1500 at 50 MPH? That would be the peak of the stock torque curve.

98rammer

25pounds of boost and your afc housing on the injection pump has been off? nope, she's been played with (stock wastegate setting is ~18psi and the normal fuel delivery wont allow the psi to go much higher if the wastegate is plugged off). a shudder is caused from bad fluid, low fluid, bad tolerenaces to the clutch packs (or warped), a warped lockup clutch, etc.

1700rpms @ 60mph with 25+ pounds of boost is right on the torque curve. transmission line pressure is controlled by throttle position (in which the valve body limits what the pump puts out) and by rpm (in which IS what the pump can put out in a general term)---and since your converter is locked at 1700rpms 60mph OD, you're putting 100% power through the transmission, or it's slipping, rather than wasting a lot of power during fluid coupling phase and not creating a situation that will cause a shudder.

if you put your foot right to the floor does the shudder go away? you can try upping the line pressure through the valve body some about 9 psi. i haven't toyed with the cable yet though. there are some things that you can do if in fact the transmission is going (which i doubt)...

Tom

jughead

it sounds like you have tq converter problem. i doubt if throttle cable ajustment will help. if the shudder seems to shake the dash it is probably the converter. raising line pressure could help some. the clutch material in the pan is more than likely coming from the tq converter clutch.

tmiller24

I have been working around a shudder since 95 when I bought my truck new. I just avoid that range of loading. I believe mine is caused by the injection pump or the injecors themselves,since the trans has been rebuilt and the converter replaced, but nothing but a plate and an overflow valve have been changed in the fuel system.

Cummnzpowr

Yes TMILLER...there are 2 kinds of "shudder" on these trucks...well, 2 that we will talk about anyway. One from moderate-to-heavy fueled rigs and their injector/injector pump shudder in lockup at low RPM {which I have REALLLLLY bad and have to manually un-lock the T/C and downshift....and there's the Torque Converter lockup shudder you get when in the right torque band of RPM from a slipping lockup clutch, and i'd be 99% positive that is the problem on his truck.They both feel the same,and it took me A LONG time to figure out what it was

Partsman

Just for giggles I'd put a bottle of Chysler friction modifer in it if you are not using Chysler ATF+ fluid. ATP makes it in a pint bottle and I don't think it will hurt anything but I'm not a trans man. ATP says lack of this will cause shudder.

richard

OK, here's a thought. Could this shudder also be coming from the clutches in the limited slip diff?
I have noticed on occasion that I get a shudder from the rear diff under the right conditions.
Just my .02
Rich

Rare1

Wow! Such wisdom. Ask and you shall receive.

98rammer. All good info. Thanks. The shudder is so rare and so brief (I back off throttle immediately to stop it), and I have never thought to floor it. Actually, I have never floored it--don't need to. Come to think of it, at 25 PSI I think the cruise control has it floored.

jughead, tmiller24, cummnzpowr. Thank you for the good info.

Partsman. ATS changed the trans fluid when they fixed the "won't shift into 1st when coming to a stop" problem. They are a high quality place and I doubt they put in other than Chrysler ATF+3. But I will ask. Thank you.

Richard. Why would you feel anything from your LSD when driving straight line? Others have reported feeling their LSD when turning. I don't have an LSD.

My conclusion thus far, a distillate of all the comments, is that my OD lockup is slipping. One solution, which I am using, is to avoid the high torque/low rpm which causes it. Another possible solution is to increase line pressure 9 psi. I have read that the various pressures in the transmission are tricky to balance, so I will go back to ATS and see what they say. I don't mind using the first solution as long as I know the transmission is reliable and won't crap out on me 1000 miles from home.

Thank you everybody for your wisdom.