vibration in drivetrain at low rpm in 4th and 5th gear

chadhargis · **Posted:** Thu Dec 04, 2008 1:10 pm

I have the Suncoast TC, which is supposed to be the Mac Daddy TC, and I still have the shudder.

I'll take a look at what I need to do to replace the U-joints if it's not a tough job and I can do it myself.

I seriously doubt that's the issue though. It for sure feels like something slipping. Since I have the upgraded TC, I'm thinking maybe it's the clutches.

retmil46 · **Posted:** Thu Dec 04, 2008 1:27 pm

chadhargis wrote:

I have the Suncoast TC, which is supposed to be the Mac Daddy TC, and I still have the shudder.

I'll take a look at what I need to do to replace the U-joints if it's not a tough job and I can do it myself.

I seriously doubt that's the issue though. It for sure feels like something slipping. Since I have the upgraded TC, I'm thinking maybe it's the clutches.

I asked Ron Woverton of Suncoast specifically about this - whether there was any need to upgrade the clutch packs along with his TC. His answer was no, for normal daily driver/towing use the stock clutch packs were more than adequate behind his TC.

However, that doesn't preclude the possibility that somewhere in the life of your vehicle the clutch packs weren't damaged in some way, shape, or form.

By comparison, replacing the u-joints is an el-cheapo mod. If that cures the problem, you just saved yourself a hefty bill for pulling and rebuilding the tranny. If not, you're only out $40 tops for the cost of the u-joints and you'll have eliminated one potential cause, such that it most likely is the tranny causing your problems.

Dawgbyte1975 · **Posted:** Thu Dec 04, 2008 2:19 pm

I don't claim to know much, just beginning to learn to work on this little tractor. It seems to me that the TCM would need to be reprogrammed for higher line pressure from transmission pump if you have an aftermarket tune or chip to totally get rid of the t/c shudder. I've taken off my chip till someone cracks the tcm and is able to reprogram it. Without increased line pressure i don't see how the suncoast will help long term and the clutch packs will wear out premature. Like I said I'm no expert just trying to bring in another point of view.

Dawgbyte1975 · **Posted:** Thu Dec 04, 2008 2:50 pm

To explain myself further, I think the line pressure might be marginally enough to keep t/c locked in O/D at low rpm's. Add in inmotion or pressure box along with possibly worn clutch plates that might be what some of us have been experiencing. Also this would explain why it goes away at higher rpm's due to the higher line pressures.

Dawgbyte1975 · **Posted:** Thu Dec 04, 2008 2:58 pm

PressureLoc Transmission Kit

A BD PressureLoc increases convertor lock-up clutch applied pressure on 1994 to 2001 Dodge trucks by 30% at light throttle pressure. The kit can easily be installed on the stock transmission and assists in preventing convertor shuddering and transmission slippage.

Torque convertor clutch slippage results in high heat and eventual transmission failure! The higher the HP, the lower the transmission line pressure is, because line pressure is controlled by the position of the throttle pedal. The diesel has so much torque at light throttle pedal movement and thus low apply pressure at the lock-up clutch when the engine is at its peak torque!

You can notice a shuddering torque convertor under throttle at low speeds, and also under heavy throttle with high power engines.

The kit’s function is to increase the transmission line pressure when the lock-up clutch is engaged. The PressureLoc cylinder rotates the transmission's throttle valve shaft to simulate 3/4-throttle travel to increase the line pressure to 90% of what the valve body design can attain at wide open throttle. The resulting pressure must be measured and set when the kits are installed.

The PressureLoc is primarily designed for stock or mildly enhanced engine applications and owners whom have installed an exhaust brake and want some extra protection.

It is not a replacement for a modified valve body!

High horsepower and heavy-loaded applications should also be equipped with the BD Valve Body with larger porting for pressures up to 180 psi.

The PressureLoc increases the clutch applied pressure to 90% of what the valve body is capable of achieving at full throttle when you are only at 1/4 to 3/4 throttle travel. This kit addresses the need for more clutch holding pressure.

This pressure increase remains within the valve body design. The stock valve body has 4.0 G.P.M flow when the torque convertor is locked up with the PresureLoc engaged. Without the pressure lock engaged, this pressure will be 4.0 G.P.M or less, depending on throttle pressure.

I wish they made one of these for the CRD.[/i]

ATXKJ · **Posted:** Thu Dec 04, 2008 3:03 pm

most folks do the Trango shift kit at the same time as the Suncoast
http://www.suncoastconverters.com/Jeep/jeep_products.html

chadhargis · **Posted:** Thu Dec 04, 2008 4:42 pm

I've got the transgo kit too.

Still have the shudder.

Ranger1 · **Joined:** Mon Oct 17, 2005 7:40 pm **Posts:** 1137

chadhargis wrote:

I have the Suncoast TC, which is supposed to be the Mac Daddy TC, and I still have the shudder.

I'll take a look at what I need to do to replace the U-joints if it's not a tough job and I can do it myself.

I seriously doubt that's the issue though. It for sure feels like something slipping. Since I have the upgraded TC, I'm thinking maybe it's the clutches.

Pull a sample of transmission oil with a new clean plastic line and have it analyzed. If your clutches are wearing to the point of shuddering, it will show up as increased wear metals. $22-$25 for an analysis will let you know for sure.

Replacing the UJpoints isn't difficult if you're moderately handy with wrenches and the cost is low for a good set of greasable Tom Woods or other high quality UJoints. A couple of hours and you'll have it done while you wait for the lab results. If it cures the ill, you'll still have a good wear metals baseline on your tranny.

chadhargis · **Posted:** Thu Dec 04, 2008 6:58 pm

I did some research on how to change U-Joints, and it doesn't look too tough. It's a little like doing wheel bearings in my motorcycle wheels.

I need to climb under my Jeep and see how hard it is to get the driveshaft out. I'd rather replace the U-joints on my workbench than under the Jeep. As long as I index the driveshaft to the output and input shafts, then I shouldn't have any issue.

Ranger1 · **Joined:** Mon Oct 17, 2005 7:40 pm **Posts:** 1137

chadhargis wrote:

I did some research on how to change U-Joints, and it doesn't look too tough. It's a little like doing wheel bearings in my motorcycle wheels.

I need to climb under my Jeep and see how hard it is to get the driveshaft out. I'd rather replace the U-joints on my workbench than under the Jeep. As long as I index the driveshaft to the output and input shafts, then I shouldn't have any issue.

15 minutes. Index the driveshaft for reinstallation. Remove 4 bolts on the rear driveshaft flange. Pull out the other end from the TC yoke.

A UJoint press and some C clip pliers is pretty much what you need to replace them.

chadhargis · **Posted:** Fri Dec 05, 2008 12:21 pm

I don't have a U-Joint press, but from what I read, you can substitute a C clamp and some sockets.

This weekend I'm going to climb under the Jeep and see what I can see. Many times, something that SHOULD be simple is not. Especially given the probability of corrosion and gunk on the U-joint that will make it difficult to remove.

Has anyone got a part number for a good replacement part?

Ranger1 · **Joined:** Mon Oct 17, 2005 7:40 pm **Posts:** 1137

chadhargis wrote:

I don't have a U-Joint press, but from what I read, you can substitute a C clamp and some sockets.

This weekend I'm going to climb under the Jeep and see what I can see. Many times, something that SHOULD be simple is not. Especially given the probability of corrosion and gunk on the U-joint that will make it difficult to remove.

Has anyone got a part number for a good replacement part?

If you have a socket that fits the old ujoint bearing cap (inside the socket) and contacts the yoke ears correctly on the outside, it'll be simple. I didn't and wasted all kinds of time with the socket slipping off many times, once I had the driveshaft off the vehicle.

On my spare driveshaft, a cheap ujoint press reduced the removal and installation time of the ujoints themselves to about 20 minutes total, working slowly and being careful to not bind the new bearing caps on installation. In my case, not having the right tool to press out the old ujoints made a simple job needlessly difficult.

Both RockAuto and Tom Woods (you have to call Tom Woods) have 1310 super strength greasable joints. The pn's vary with the brand.

Good luck.

danoid · **Posted:** Fri Dec 05, 2008 10:12 pm

kb61751 wrote:

I just have a hard time accepting that its the u-joints causing the problem. Drive shaft load and speed would be the same (or greater)at other load\transmission ranges. I feel it may have something to do with the engine load at that speed (1600-1800 rpm), which is only held there under load for any long time when the transmission is in TC lockup. I vote for a fuel issue (air, overloaded, etc). The other is that the TC is slipping when locked up, but at 2000 rpm where the most torque is developed it does not make that noise, so I don't think its that.

Agree somewhat. I'm not ruling out fuel, here's other ideas.

What's the common factor with the originally described issue? Engine speed. Ergo, it's engine related.

As any driver of a manual transmission will tell you, if you lug an engine, it rattles. Four in a row (while may make it go) is one of the worst configurations for engine vibration. A high torque / low rpm diesel makes the situation worse.

The engine mounts are the culprit in my opinion, coupled with the general unibody structure of the vehicle. At certain engine speeds, the inherent imbalance of the 4 cyl 'lights off' portions of the unibody at their resonant frequency. The engine mounts do a poor job of isolating the engine from the unibody, hence our relatively high torque converter lockup speed (1600 rpm vs. 1100 rpm in my V6 minivan). The reason I bring up a minivan, it that the 2.8L VM tractor engine is also used in Chrysler's (not available in US) minivan. Different mounts + better body structure = smoother operation.

A suggested fix (and not a relatively easy one I'll admit) is to loosen the top end of both engine mounts, gently lift the engine off of the mounts, and set it back down straight. Then retighten the mounts. This will relax any preload of the mount (more engine weight on one mount or the other).

Another thing to check (it happened to me) is to make sure all of the transmission bellhousing bolts are at their proper torque. Golling Chrysler/Jeep (may they rot) neglected to perform this simple task when performing my F37(?) recall. (They also neglected to flash anything - mabye that's why it failed again in a year.) My symptom of this one was a dashboard rattle, but the driving frequency usually determines the response.

Also, check the whole air path. A leak on the intake or exhaust side could destabilize the engine only at specific engine speeds/loads.

My 2 cents.

kb61751 · **Posted:** Fri Dec 05, 2008 11:37 pm

I agree fully.

chadhargis · **Posted:** Sun Dec 07, 2008 3:38 pm

Interesting thoughts. Although I don't think I have the provisions to loosen the mounts or lift the engine.

A friend of mine who is a transmission specialist came by yesterday and I took him for a ride. He told me it felt like a "harmonic" issue. He said that an engine turning at a certain rpm can generate a resonance in the vehicle and that manufactures typically put weights on the driveline somewhere to compensate.
We climbed under the vehicle and sure enough, there are weights under there. He pointed them out to me.

He told me that if I'm going to do the U-joints, and I'll be removing the drive shaft anyway...to put the Jeep in Full Time 4wd and go for a ride using just the front wheels to power the Jeep. With the drive shaft removed, I can rule out bad u-joints or driveshaft balance or harmonic issues.

He said if it still does it, then you know you have something in the transmission itself.

He is a big Dodge fan, and is familiar with the transmission in the CRD. He told me that they are actually pretty good transmissions, and he's never seen many major issues with them in his years of rebuilding transmissions. He told me that since I had replaced the TC, that I could rule that out. But he did say that I might not be getting enough line pressure at that low of an RPM.

So...the answer may be to increase the line pressure. Is there a way to do that?

BlackLibertyCRD · **Posted:** Sun Dec 07, 2008 3:45 pm

When you did the suncoast TC I hope you put the pressure valve springs from the trango kit in the new front pump. I don't know any other way to boost the pressure. I think the TC is only half the problem like your friend said, more pressure is needed.

Ranger1 · **Joined:** Mon Oct 17, 2005 7:40 pm **Posts:** 1137

Quote:

He told me that if I'm going to do the U-joints, and I'll be removing the drive shaft anyway...to put the Jeep in Full Time 4wd and go for a ride using just the front wheels to power the Jeep. With the drive shaft removed, I can rule out bad u-joints or driveshaft balance or harmonic issues.

GMCTD posted the resistor mod (the one that TransGo uses) for raising line pressure as well as a suggested different resistor value and the pin #'s to connect it to in the engine bay computer wiring. I think he wired his to a toggle switch on the dash so he could use it while towing. Search his posts for that one.

BlackLibertyCRD · **Posted:** Sun Dec 07, 2008 6:15 pm

I believe the resistor is to modify torque management and goes between pin 1 and 3 on the transducer plug. The instruction in my kit says not to use it if your running a chip.

chadhargis · **Posted:** Sun Dec 07, 2008 6:29 pm

I did purchase the TransGo kit, and I ASSUME my dealer put it in like he said he would, but you never know.

Ranger1 · **Joined:** Mon Oct 17, 2005 7:40 pm **Posts:** 1137

BlackLibertyCRD wrote:

I believe the resistor is to modify torque management and goes between pin 1 and 3 on the transducer plug. The instruction in my kit says not to use it if your running a chip.

Way back when I first considered the Transgo I called them and asked about the resistor. They told me it was to spoof the computer into raising line pressure. They didn't say how they did it, either with lowered pressure readings to the TCM/PCM or modifying the torque management. Either way, it's causing firmer shifts, to the point where iirc, gmctd suggested using a different value resistance for experimentation to see if that eased some of the harsh shifting complaints.

vibration in drivetrain at low rpm in 4th and 5th gear

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