suncoast installed but shuder still there... not good.

jinstall · **Posted:** Tue May 05, 2009 6:25 pm

just to add, my KJ has always had a 92-99mph driveline vibration, since new.

chadhargis · **Posted:** Tue May 05, 2009 8:30 pm

+1 on the Dr. Tranny. Worked for me.

ihavelotsoftoys · **Posted:** Wed May 06, 2009 8:34 am

About the shudder changing with the Suncoast: The suncoast has improved damper springs in the clutch assy, so it isn't surprising that the shudder changed a little. Also the Suncoast has a little more mass to it. That's going to change the resonance of the system. I am guessing that the design of the drive train has some resonance peak that stresses the TC clutch. Suncoast says that the clutch in their converter is much beefier than original and that they put better (i guess larger or stiffer) damper springs in the clutch. I guess I will try to increase the line pressure with the transgo resistor. If that doesn't provide enough holding power I will have InMotion shave a little torque off in the 1800-2100 RPM range. If I can't change the characteristics of the system, I will have to apply less power. Bummer, I really like the stage 2 from InMotion.
Has anyone on the forum messed with the driveshaft or flex plate on the back of the engine? I noticed the flex plate was quite springy and that the drive shaft has a huge mass on it near the yoke where it goes into the trans. All this makes for one big slinkey spring that sure can get excited when 700CC diesel jugs pound on it. If this system of masses and springs are not properly designed the clutch could easily see 5X peak torque pulsations!
Has anyone taken off the mass at the yoke? It would pass more vibration to the differential, but it may lower the frequency of the system and move it down from the 50-65 mph range.

nursecosmo · **Posted:** Thu May 07, 2009 12:12 am

ihavelotsoftoys wrote:

About the shudder changing with the Suncoast: The suncoast has improved damper springs in the clutch assy, so it isn't surprising that the shudder changed a little. Also the Suncoast has a little more mass to it. That's going to change the resonance of the system. I am guessing that the design of the drive train has some resonance peak that stresses the TC clutch. Suncoast says that the clutch in their converter is much beefier than original and that they put better (i guess larger or stiffer) damper springs in the clutch. I guess I will try to increase the line pressure with the transgo resistor. If that doesn't provide enough holding power I will have InMotion shave a little torque off in the 1800-2100 RPM range. If I can't change the characteristics of the system, I will have to apply less power. Bummer, I really like the stage 2 from InMotion.
Has anyone on the forum messed with the driveshaft or flex plate on the back of the engine? I noticed the flex plate was quite springy and that the drive shaft has a huge mass on it near the yoke where it goes into the trans. All this makes for one big slinkey spring that sure can get excited when 700CC diesel jugs pound on it. If this system of masses and springs are not properly designed the clutch could easily see 5X peak torque pulsations!
Has anyone taken off the mass at the yoke? It would pass more vibration to the differential, but it may lower the frequency of the system and move it down from the 50-65 mph range.

And again, if it were tortional ossilation, it would not change at all with the addition of friction modifier. The case however, is that everyone who has added friction modifier to their transmission has reported dramatic improvement in the chatter. I'm betting that the transgo shift kit will also help a lot.

grommet1 · **Posted:** Thu May 07, 2009 12:14 am

After recently receiving a new factory installed torque converter under warranty, and still getting the shudders, I made up my mind to just live with it and just keep hoping for a cure...One thing I did at 36,002 miles however was to start operating in ORM. I do not mind the extra clatter in exchange for less smoke, extra power and improved economy, nice! One thing I have noticed is that while operating in ORM the shuddering is not as bad, really. I also have a hard time forcing it to shudder at will as I always have been able to do.
Not sure how this info fits into our little common problem, just thought I would throw it out there.

brew1 · **Posted:** Sat May 09, 2009 1:19 pm

Where are you guys purchasing your Dr. Tranny friction modifier and are you using 2 tubes? Just for $hits and grins, I'm gonna give it a try.

nursecosmo · **Posted:** Sat May 09, 2009 11:03 pm

Bought mine at Napa. Orrileys also has it.

gmctd · **Posted:** Wed May 20, 2009 1:35 pm

I'd pay five bucks to see the look on someone's face after removing that torsional damper mass from the driveshaft - btw, friction modifiers don't make it hold better - they make it slip smoother at breakaway - that's why they're required in certain types of limited-slip differentials, notably those with multiple-clutch packs, but not in those with steel-on-steel dog- or cone-type mechanisms

My KJ never shuddered with the new oem TCC and Edge Trail - it never shudders with Inmotion, Edge Trail, Suncoast, and Transgo - 'course, it does sit 2.5" taller than stock (greater driveline angle), with 2.55 Goodyears (increases driveline loading at all rpms) - and running DCJ recommended ATF+4 - however, the normal 4cyl 2-distinct-power-stroke-per-rotation pulsing can be induced at will, as with all 4cyls at lower rpm - get'em up above 2500rpm and you'll barely feel a thing, tho the larger the displacement, the higher the rpm B4 it totally smooths out - try a Cummins BT3.9 for a real comparo-thrill

A set of anti-wrap bars on the rear axle could help, but may move the 4cyl shudder lower in the rpm band - it is a large-displacement 4cyl hi-tork Diesel, after all - early Astro vans had single-leaf fiberglass rear springs, similar to the Corvette's single transverse rear spring - the '94's got steel multi-leaf versions intended to eliminate that annoying large-displacement V6 driveline shudder into the floorpan - the Astro is uni-body construction with a detachable subframe for the engine and front suspension, similar to the KJ........................

Btw - my TCC slips into full lock at ~53mph - musta not been totally F37'ed at the time of the replacement oem TCC, Apr07, 5mos B4 I got it - Suncoast\Transgo went in Nov07

MOSFET · **Joined:** Sat Feb 25, 2006 11:40 pm **Posts:** 295

brew1 wrote:

Where are you guys purchasing your Dr. Tranny friction modifier and are you using 2 tubes? Just for $hits and grins, I'm gonna give it a try.

Try one tube first. I bought two, but one did the trick. That shudder is 80% gone, and barely noticeable now. I don't know how long it will last, but it was well worth the price.

nursecosmo · **Posted:** Wed May 20, 2009 5:13 pm

gmctd wrote:

btw, friction modifiers don't make it hold better - they make it slip smoother at breakaway - that's why they're required in certain types of limited-slip differentials, notably those with multiple-clutch packs, but not in those with steel-on-steel dog- or cone-type mechanisms

Uhh...no. A friction modifier is just that, it modifies friction either up or down.

They come in many flavors including super slippery tri-nucleic molybdenum which is used in high performance engine oil. Try putting that in your tranny and you will just spin the clutch plates against each other and go nowhere.

A second kind of modifier is used in limited slip differentials and is known as a dynamic friction modifier. It is composed of mainly long coiled organic polymers which thicken up as pressure is applied in the thin film boundary. This achieves a smooth transition between static (locked up) state and open state.

The third kind of friction modifier is a static friction modifier. This is the one used in ATF fluid along with moderate amounts of dynamic friction modifier. It greatly improves the static, "lockup" ability of the clutch surfaces. It does NOT help with the break away smoothness of the clutches, which is why a small amount of dynamic modifier is also used. If you put ATF friction modifier into a vehicle with a slipping transmission (even if it isn't chattering), it will in many cases eliminate the slippage and buy a few more miles before a rebuild. Do NOT use this kind of FM in a limited slip diff, unless you wand to grind tires on every corner. As an interesting experiment, next time you are drilling a hole through metal, put some friction modifier on the bit instead of oil.

The moral of this story; use Dr Tranny for very noticeable improvement in your vehicles performance.

gmctd · **Posted:** Wed May 20, 2009 7:00 pm

Almost true - so, let's add a can of medic to an old transmission, beginning to act it's age: slipping, sluggish, erratic - we've just poured in a quart of solvent which thins the oil, making it less slippery - also helps in flushing out clutch paks and galleries and valves in the body, all filled with that brown stuff we find in the bottom of the pan, soon making for quicker apply\release, improving response - another component softens the soft-seals, making them more pliable, improving response, less leaky - also swells those soft seals, further reducing leakage and improving apply pressures - now our old trans, in it's golden years, begins to respond like it's only in it's silver years

However, we wouldn't want that gunk in our low-mileage juvenile transmission, which may appear to be shuddering in lockup, because: the TCC in this, and many other modern automatic transmissions, does not lockup - TCM applies pressure just enuff to achieve correct crankshaft\input shaft slip angle required to move the vehicle - TCM is constantly monitoring the slippage, varying apply according to torque vs load requirement, but the TCC is always right at breakaway point, just below slipping slightly, never 100% locked up - let's add some friction modifier to improve lockup, and the response would tear the t\c apart - but wait, let's add some friction modifier to improve breakaway slippage, and viola! - reduced shudder - maybe

My KJ CRD does not 'shudder' unless I want it to, as does my Cummins 5.9, and my GM 6.5 - it's called 'lugging', where the individual power strokes may be experienced at low rpm - lugging rpm would have a much broader range with a 4cyl Diesel..................................

nursecosmo · **Posted:** Wed May 20, 2009 7:53 pm

gmctd wrote:

Almost true - so, let's add a can of medic to an old transmission, beginning to act it's age: slipping, sluggish, erratic - we've just poured in a quart of solvent which thins the oil, making it less slippery - also helps in flushing out clutch paks and galleries and valves in the body, all filled with that brown stuff we find in the bottom of the pan, soon making for quicker apply\release, improving response - another component softens the soft-seals, making them more pliable, improving response, less leaky - also swells those soft seals, further reducing leakage and improving apply pressures - now our old trans, in it's golden years, begins to respond like it's only in it's silver years

Uhh....no, no, and no. GM you don't usually don't speak about things which you don't have a clue on, but in this case you are. Dr Tranny is not a quart of solvent. It is about 2 ounces of pure friction modifier. It has no solvent, no thinning agents, no emulsifiers, No seal softeners, just whatever particular chemical they use to improve lockup, in fact it is quite thick compared to TF.

gmctd wrote:

However, we wouldn't want that gunk in our low-mileage juvenile transmission, which may appear to be shuddering in lockup, because: the TCC in this, and many other modern automatic transmissions, does not lockup - TCM applies pressure just enuff to achieve correct crankshaft\input shaft slip angle required to move the vehicle - TCM is constantly monitoring the slippage, varying apply according to torque vs load requirement, but the TCC is always right at breakaway point, slipping slightly, never 100% locked up - let's add some friction modifier to improve lockup, and the response would tear the t\c apart - but wait, let's add some friction modifier to improve breakaway slippage, and viola! - reduced shudder - maybe

Uhh...no. Of course it locks up. That is why it is called a "lock up clutch". While true that the TCM is constantly monitoring the slippage rate, it does NOT normally allow slippage. It is always wants to use the minimum pressure necessary for complete lockup for improved fuel economy. As soon as it detects any less than a 1 to 1 conduction ratio, it applies more pressure so that there is NO SLIPPAGE. It uses adaptive learning software so that once it detects slippage at a certain engine load and RPM, it will not allow it to slip next time the same situation is encountered. If slippage were constantly occurring, the TC Clutch would be toast in a very short time, plus the entire advantage of a diesel engine - it's torque - would be lost. GM, if you are concerned about your TC clutch being in full lockup, I would uninstall your Transgo shift kit post haste. And again, the kind of friction modifier in ATF additive is NOT dynamic friction modifier, as used in LS differentials. It is static friction modifier, which ALL modern auto trannys have to have. Put mineral oil in your modern tranny, which would allow the most slippage and see what happens.

gmctd · **Posted:** Wed May 20, 2009 9:02 pm

You posted while I was proof-reading - so, I didn't get to edit-in that prior to adding the quart of medic, one must drain a quart of atf - but it does affect an old trans in the manners as posted - 'course, the results are never as satisfactory as a rebuild

Nor did I get to edit-in the second para that TCC apply is never 100%, apply is always modulated at just above breakaway, no more - the solution would depend on whether TC friction was too great or too little, either way resulting in more aggressive modulation, which could contribute to the observed shudder - correct proof would be from a scantool, monitoring % of apply vs slip-angles during event of shudder - which mine does not

So, back from a Hemi T\C quest:

I have not squirted a tube of cure in my 545RFE, because there is no shudder

EDIT: SGII could be utilized to observe this phenomena

ihavelotsoftoys · **Posted:** Wed May 27, 2009 1:14 pm

While you guys were ranting, I got around to installing the transgo resistor. NO CHANGE IN SHUDDER! Wow. Now what? It did change the 2-3 upshift performance so I know it was installed properly. I drove it for around 50 miles to be sure the shudder didn't change, but no. So this is looking like it may not be the TC clutch slipping. Or we may have two problems.
I also drove to the mountians with about 1000 lbs in tow this weekend. (this was after i removed the transgo resistor). I didn't burn out anything. In fact while climbing hills I kept it in the range where it shudders. Nothing broke, just lots of buzzing and vibration. The engine rpm's didn't increase quickly that would signal something slipping. I will continue to try to break this which was Suncoast's suggestion. The TC comes with 2 year replacement or fixit promise. Ron at SC said if clutches are slipping it should go to hell in a handbasked quickly.
I will drive some more and check the fluid for discoloration and odor. Maybe even an oil analysis, but not sure they can pick up burning clutch material.
The shudder happens just after lockup in 4th or 5th gear. It starts a about 53-55 (wherever lockup happens) and continues to about 65 or 70ish if you stay on the pedal. Any time the vehicle is in that speed range applying a fair bit of throttle causes the shudder. Engine RPM ranges for the shudder are about 1800 to 2100.
Does any one know of a drive shaft shop that has accelerometers and serious diagnostic tools?
Anyone know who makes a drive shaft with one CV and one U joint?
I am either going to fix this or get pissed off and sell the darn thing.
BTW I am lucky to get more than 20MPG with Transgo, Suncoast and InMotion stage II

Turbo Tim · **Posted:** Wed May 27, 2009 9:46 pm

Hmmmm. You say lockup at around 55 MPH? Do you know if you have been F37'd? This could explain some of it.
If you have had the stealership replace the torque converter and they reflashed your computer, lockup should occur at about 63 MPH.
If not, then the good original tune happens around 57 MPH?

Let us know.

nursecosmo · **Posted:** Wed May 27, 2009 10:40 pm

Those ranges are not even close to what I was experiencing. I could only get shudder @1600-1700 RPM. It would shudder at 4th lockup @50mph and 5th lockup only after I had backed down from 60MPH where it locks up to 56MPH. I have never been able to get it to shudder past 1800RPM. Ever since the new TC and two tubes of DR Tranny, I can only make it happen on a steep hill with a heavy load.

ihavelotsoftoys · **Posted:** Thu May 28, 2009 10:41 am

Mine locks at 53-55 MPH for sure! It is in fourth gear when it locks. It makes a final shift at around 60-65 depending on how much throttle you are giving it.
I know I have F31 mod (dealer applied sticker in engine bay before I bought the car) but never had it into a stealership for new TC or flashes. I avoid them like the swine flu!
Before suncoast, I could get it to shudder with OD off and around 40MPH. With OD off my TC locks at 40MPH. It's in third before the lockup. Now with suncoast, stronger lockup and no shudder in 3rd with lockup.
Before suncoast, when it shuddered in 4 or 5 and speeds greater than 55 MPH you could observe engine speeding up quickly. Just like when the clutch slips in a manual trans car. Dont' really see that now with the SC. If it is slipping it's just a little bit!
I really want to fix this POS, cause it's fun to drive with the SC and InMotion II! Just worried the shudder will eventually break something. If it isn't a clutch (lockup or OD clutch in trans) something is going to break and it won't be pretty!

nursecosmo · **Posted:** Thu May 28, 2009 12:18 pm

So Drop a couple of tubes of Dr Tranny in it and be amazed. You cant hurt anything at this point.

gmctd · **Posted:** Thu May 28, 2009 1:30 pm

I agree - fyi, I have not been advocating against the stuff, merely trying to analyze\pinpoint the source of the symptom, as some KJ CRD's doit, some don't - mine's jacked a little with larger tires, which I've reset the ratios so as not to upset the ABS, TCM, and ECM, but no shudder unless I'm wanting to feel the power strokes - also do that sometimes with my Dodge\Cummins, just to get a sense of the immense low-rpm torque - power strokes in 6th gear in that big 3500 will quickly remove the plaque from your teeth

nursecosmo · **Posted:** Thu May 28, 2009 1:36 pm

You know that we're always cool GM. I don't get too worked up about anything I read on the forum, and hope that I don't get taken too seriously by anyone else.

suncoast installed but shuder still there... not good.

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