LBZ Matched to a 4L80e Vibration

[poyntern]

I am wondering if anyone has any ideas as I am at my wits end with this one.
I recently swapped a LBZ into my 99 CrewCab (OBS) ShortWheel Base 4X4. I left the 4L80e behind it. ( I know, I know, it won't last, but I'm pretty easy vehicles so my fingers are crossed). So far just for cruising around its been fine.

The problem I'm having though is a vibration between 1900 - 2300 rpm when in park, neutral and or running down the high way.

The technical details. Stock LBZ, EGR Delete, Intake Air Heater removed, Stock Ring Gear, 06 G3500 Van Flex Plate, GM Torque Converter Bolts, Stock 454 Converter on the 4L80e. I researched this to ensure I was matting the two up as GM did in the vans. (I hope I got it right?)

I have run the engine with the transmission slid back, with no contact whatsoever, and the engine has no vibration at any rpm range.

Slide the transmission back and bolt it up and the vibration is back. This is in park.......no wheels in motion, no driveshaft turning just the converter etc.

The truck is very drive-able at all other rpm ranges. 2600 rpm is great as is 1800. But at 1900 - 2300 I think the trans is coming up through the floor.

I'm posting because I am days away from pulling this combo out and putting in another LBZ/Alli that I have sitting on my garage floor that is completely stock.

I can not stand vibrations and this has me twisted up pretty good.
I don't think its worth puling the tranny and going through it......if that would even solve the problem......if I need to to that I might as well put the Allison in. The transmission when the 454 slug was in front it was fine. No vibrations. It's only since the DMAX came along......and maybe that's it. Have I already broken it and this is just the beginning.

So I need some advice......is that what it's going to boil down to?

Thanks in advance,
Norm

 

[Stingpuller]

Tranny

I'm no tranny expert but to me it sounds likethe convertor. If it's fine unbolted then I would think it has to be the convertor. Yhe only thing turning when in park is the input and drum. I don't think anything there could be a problem. Jeff

 

[dmaxfireman]

was the trans full of fluid and driven on the road? i wonder if the converter is not full of fluid yet.

 

[Mike L.]

Couple of questions.
Was the 4L80 converter a rebuilt unit? Could be out of ballance. What is the gap distance between the front of the converter and the flex plate with the converter shoved all the way back into the trans? Could be you are drawing the converter out of the pump too far.

 

[Stingpuller]

Tranny

Does the convertor have the correct pilot size for the crank?

 

[Mike L.]

Does the convertor have the correct pilot size for the crank?

I looked that up and they are Jeff. But if the converter is too short it won't enter the back of the crank.

 

[poyntern]

Thanks guys for the responses.
The converter is an original GM. The truck had 172,000 km's on it when I started this and to my knowledge and from the appearance the transmission and the 454 had never been apart. (really an original unmolested truck)
With the converter all the way back (going from memory here) there was a an 1/8 to maybe 5/16 of an inch gap between the flex plate and the the lugs on the converter.
So I think that should be ok with respect to spacing? and again this is from memory as I really did not inspect this at the time. It did seem normal though as I was installing the bolts. Just the way it worked I found it easier to shove the converter back and install the bolt through the starter access and the hole in the ring gear. Its not a pleasant job as I'm sure you know and in my truck the starter will not come out. So it needs to be wrestled as far forward and down as possible to get a socket and a swivel in to put the bolts in the torque converter. All in all I would have to say I think this spacing was fine. (of course now I'm seconded guessing)

From what I could tell when I slid it back, the converter was the correct size for the end of the crank. But I did not measure this and had limited space to investigate it as well.

As for fluid, there was a deeper pan put on at the time of conversion as I was fearful of temps and saving the 4l80e as long as possible. I also had to use a lokar dipstick tube. During this time I had some help with the install and I did not personally measure the quantity of fluid that went in the transmission. On Saturday when I reassemble this, I did check tranny fluid and it was low. I added about a litre (sorry for all the metric). Never has the transmission slipped or refused to move. Its always functioned fine, but had this vibration. THus, I had not thought about fluid prior to this and had trusted my colleague who filled it to begin with.

Not sure I've added much information which will help resolve this one.

Any other thoughts? Or is it doomed?

My next dilemma is do I pull the whole thing out and put in the factory mated LBZ/Alli/Transfer Case I have.....or do I just swap in an Allison and Tcase and go from there. My fear is I will create yet another vibration.
You know Murphy's law????? I once had a dog named Murphy.....for that exact reason!

Thanks Everyone appreciate your insight and your time,
Norm

 

[chevy791979]

Couple of questions.
Was the 4L80 converter a rebuilt unit? Could be out of ballance. What is the gap distance between the front of the converter and the flex plate with the converter shoved all the way back into the trans? Could be you are drawing the converter out of the pump too far.

i have built a good number of these trannys............is there any sign of "counter "wieghts on the conv. ? Any front pump leaks>? if so check the input shaft for runout.

does the truck do it while in first ................reverse ...............third?

ive seen shafts bend in these 80's from farmers pulling 80K worth of wet corn (jk) but way too much weight and too much right foot.

if you can get a slip yoke (empty) run it through 1st an reverse only (it will do funky shit if it shifts) see if the vibe goes away.