I was about 20 miles away from home after a 1200 mile trip in my 98 6.5 td and I felt like I was on a rumblestrip going about 60 on the interstate, but there was no rumblestrip. Turns out the truck would make that rumblestrip vibration anyplace I could get it up to 50 and let off then get back into it witht he converter locked up. It went away in 3rd gear and never happened in other gears. I had no idea what it was until I talked to a tranny guy locally and he said it was a bad torque converter. Unfortunatley I broke my crank before I figure it out.

Do you think the torque converter really was bad? If you agree it was the converter do you think that caused my crank to break back behind the rear most main bearing?

Right now I have a motor with a leaky head gasket, broken crank and maybe a bad torque converter in the tranny. Good times......

They can become pretty violent. Really sorry to hear about it.

My 2 door Tahoe with the optional 6.5 Turbo diesel had the same problem.

It happened every time the transmission shifted out of over drive. I took it in to a local transmission shop that I trust and they told me that the torque converter was causing the problem that felt like I was running over rumble strips in the pavement.

I also had noticed that from time to time it felt like it did not want to stay in high gear. As I drove at a steady speed it would feel as if the transmission had slipped into neutral. To make a long story short at 309,000 miles I had the torque converter replaced and the 4L80E rebuilt. This was the first trouble the Tahoe has giving me.

I talked to another very knowledgable mechanic near me and he agreeed that my torque conver broke my crankshaft. He said it mast have ahd a broken plate inside. It is scary because I only drove it a week after it started doing it and most fo the driving was around town when it wouldn't vibrate.

My Suburban has started doing this again recently. The first time, I did a fluid and filter change, and it was fine for a whole year. Recently it started doing it again. It only does it when coming out of lockup slowely (i.e. a gentle acceleration uphill). If I force a quick downshift, it is fine.

I was going to replace the fluid again, in hopes of prolonging it. Are there any other options to try and prolong the life of this (i.e. friction modifiers that would prevent clutch chatter)? Or is my only hope to replace the converter? I've seen a number of people have trouble with replacement converters. Are there any recommendations as to where to buy a good stock replacement?

It's not very comforting to know that the chatter can cause the crank to break.

Don.

Are you sure you don't have a bad harmonic balancer that was causing the vibration and broke the crank?

Gary

I really don't know hat a bad harmonic balancer would look like.

Here is what a good one looks like!:)
http://www.am-autoparts.com/AM/Harmonic-Balancers/GMC/Savana/-/AM-10469017/?utm_medium=shoppingengine&utm_source=google_baseSF

Most broke cranks in the 6.5 seem to be from the harmonic balancer going bad.
Just run a quick search and you will find plenty of threads.

Gary

A Bad one will have a crack all the way around in between the inner cast pully and the outter part you put the belt on.

As I was browsing a link to a transmission site in another post, I came accross an apparent fix for TCC shudder. Apparently the osscilation of the TCC shuttle valve can wear the bore of the valve body and lead to TCC shudder. Their fix is an anodized aluminum valve, with a teflon seal, and the option of two springs for stock or a firmer TCC engagement. Has anyone heard of this being the cause of TCC shudder? Does this seem like a reasonable fix for a transmission already showing these symptoms?

The cost is not that much (far less than a new converter), and I know valve body wear is a problem on these transmissions.

Any thoughts, opinions, experiences?

Don.

My 96 is doing the rumble also. Roughly at 174,000 miles right now... So you did a trans flush and it helped awhile longer? I'm thinking this might be a good idea! I just lost the lift pump yesterday so this could be done at the same time.
later
Mike

I didn't actually flush the trans, just drained and refilled... only what came out by dropping the pan to do the filter. So probably only changed half the fluid. But yes, it made a difference on mine for about a year. But now I'm trying to find an answer that doesn't involve a yearly fluid change on the trans (and I really wish the answer wasn't a new torque converter)!