99.5 DRW, 37" tires.

In a little over 1 year my truck has eaten 3 flexplates, I did the tsb about changing out just about every mating component between the engine and trans. Spacers, TC, Flexplate I also took out the previous owners shift kit and put in a bully dog shift kit. I also got a different valve for the transmission pump from the guy I bought the new Torque Converter from. It now has very firm shift 1-2 but can BANG 2-3 pretty hard on occasion. I also removed the chip and took the engine back to stock except for the 4 inch duals.

This last Flexplate lasted a Month to the day before cracking, I havent even taken it apart yet, I know the sound too well now. I have done no towing at all.

I would really like to know your thoughts on this, rather than just put in a billet flexplate which seems like it will just cover up the real problem. Someone has said the harmonic balancer could be causing it, which is really the only thing left. Has anyone seen any excessive crank runnout?

 

Well you're more clever than I gave you credit for right off of the bat. I got to your last paragraph and realized that someone else has already suggested to you my first thought. Something is out of balance and if it is not something really out of whack internally it's got to be the harmonoic balancer.

 

The motor runs excellent and has plenty of power so I hope its nothing internal.

Unbalanced does make sense since the second time it broke on me was while it was idling. I had to jump start my line truck (completely dead) and left my truck hooked up to it for 45 minutes, all was well till I finally noticed the engine getting louder and louder (chatter) like it just went bad just sitting there.

Whats odd is the thing must have been bad when I bought it, it had no chatter noise however, it did have a little more vibration than what I now know as normal. I found the previous owner must have gotten sick of replacing them and let it go until the flexplate rewelded itself in 2 spots and traded in. There was a 1/4" of clearance around where it broke except for the 2 spots it mashed itself together and friction welded. Funny thing is that one lasted the longest at 7 months, with some hard towing and driving. This one never did completely break out the center for me, the thing actually twisted and the starter wasnt hitting the teeth anymore.

 

Did you remove and measure the thickness of the cast aluminum gear cover (between the engine and trans)? This part being machined off parallel was the root cause of repeat flexplate failures covered in the TSB. Just changing the other mating parts (crank adaptor, bolts, flexplate, reinforcement ring) will not correct mis-alignment which is caused by a faulty gear cover.

 

Yep, I replaced it (ordered everything for the tsb)

The only thing I couldnt figure out was there was a bushing spacer on the end of the torque converter nose that 3 different dealers couldnt find on there microfiche and no mechanics in any of thier shops had seen. The first time I did the flexplate I reused everything including this spacer. The second time I replaced everything and left this spacer out since it was too dicked up to fit on the new converter. The nose reaches into the crank spacer enough that it didnt seem needed anyway.

 

1) Did you replace the machined, cast aluminum gear cover that goes between the engine and trans? It's shaped like an old "horse collar".

2) The only adaptor to the torque converter pilot should be the crank adaptor which is bolted to the end of the crank. Can you post a pic of this "extra" part?

 

I am on my third flex plate. When the first one went, I thought I lost a piston or something internal. Sounded real bad and took me quite a while to figure it out. The second went out about 6 months later. I knew what the problem was and fixed it rather quickly. I have since had the tranny rebuilt and torque converter replaced. So far, so good. That's been about 7 months ago.

 

Yes, I replaced the horse caller, its called "gear spacer" or something like that. I also replaced the crank adaptor (crank spacer) the torque converter aswell.

I dont have it or a camera right now, but if you think of a thick wall pipe about 2 inch in diamter, cut a 1/4" off it.. then you about have the part I removed from the nose of the old converter.

 

I developed the TSB (fix) for this problem. I don't recall the piece you are mentioning. I am digging into the archives to see exactly what parts SHOULD be there. Be patient, there are a lot of files to dig through. If you should happen to have another failure, please try to measure the thickness (all away around) of the gear cover using micrometers. This part should be machined parallel. It was found to be the root cause of repeat flexplate failures. In your case (with the "extra" part, it appears that something just isn't right. To confirm you have a 1999 w/7.3L correct? Feel free to email me directly also.

 

Yes, a 1999.5 7.3l

Aside from the year on the door (late 98) I have no idea what the previous owner did to the truck.

Im also thinking the truck may have been manual trans at one time, there is a whole in the floor for a shifter and the some of the dash had been changed and painted to match. Some say the floorpan is different from an at to manual but I dont see a whole lot of room above the AT to say it had definitely been manual before.

Thanks for the help I appreciate it, I dont have much money to keep doing this!

 

I did some checking. There should not be a loose piece as you described. If the vehicle were originally a manual, there would be differences on the attachment of the manual vs. an automatic. Manual transmisssions used a caged roller bearing as a pilot. I believe that the crankshaft adaptor was also different. If you bought ALL of the parts (by part number) specified in the TSB (including a new gear cover), then you should have the correct parts for an auto transmission. In addition, there should be two hollow dowels that line up the gear cover to the engine, and, two that line up the transmission to the gear cover. If these are missing, they could cause mis-alignment of the engine and transmission, which would cause flexplate failure. I would also suggest checking the torque converter and transmission numbers to verify that they are correct (for 4R100 transmission). The torque converter pilot should be a close slip fit into the crankshaft adaptor, and, have room inside to slide forward (as the converter will "balloon" slightly during loading). Let me know what you find out.

 

I know this is old as dirt, the end result was the dowel pins in the back of the motor. They were from the manual trans and only went into the trans 1/8 - 1/4 inch or so.

i cant remember how long they were but when on a hunch just ordered them from the dealer they came very long, put them in and they stuck out real well from the horse collar. trans went on like a glove. unfortunately I also dumped 800+ into a billet flexplate to just be done with it.

 

Nice closure. So, did you install the longer dowel pins back in '08 and you haven't had any issues since? If so, then I'd say you definitely solved your problem.

 

wow! thanks for closeing it out.

 

Parts counter started giving me a deep discount on them. So I bought 2 at a time, cut the ring gear off with a plasma cutter and laminated 2 together. Worked like a charm for about a year each. So I actually fixed it sometime in 2010. I also changed the transmission and to a billet flexplate at that time. But the difference of the dowel pins length between manual and automatic was significant.