Hey guys, this is sorta long so bear with...

I have a carb'd 540ci BBC in my 92 454ss truck along with a 4L80E transmission. It has a 3500, 10", 245mm stall from PTC. Since these trucks came stock w/the 4L80E I've decided to control the trans via the stock (ODB1) PCM.

Its been working great so far and the only issue I have a wild bucking/shuddering that happens once the converter locks up. I'm 99.9% sure its the converter as when I tap the brakes the bucking goes away. The truck runs great other then this issue.

I've been trying to fix this thing for the past few months and I need your help/suggestions. I have been mod'ing the chip in it for awhile now and I'm at a loss whether its a tuning issue or an internal trans/converter issue.

So far I've tried:

I got it to throw a DTC "Code 68" one time, which I think is is basically the ODB1 equivalent of p1870 (Overdrive ratio error). GM flowchart to diagnose this is pretty lame IMO. This means the slip was >200rpm, for 2 secs.

I do have the capability to datalog it, and its showing that the converter is in fact staying locked during the TCC shudder.

I called the PTC guys and they think the cam is too big for it, but I'm not so sure. Cam specs are: Lunati, 241/249*@.050", .661" lift, 110LS. Their suggestion is to either change the cam, turn off lockup, change out existing rear 4.10 gears to something lower, or continue to bump up the lockup mph until it goes away. Pretty much almost all of which are no-go's for me.

If you guys have any advice at all for me, it would be greatly appreciated! Thanks!

 

Maybe the converter is no good.

 

How old is the converter? It sounds like the clutch is slipping. Log the engine RPM vs the input shaft speed of the tranny. If it is slipping, you should be able to see it there.

 

ive ask a few of the guys around here about your truck Joel, and every one of them have ask the same question as in it being converter related.

Jamie

 

The PTC guys don't seem to think so, but I think its a good possibility..lol


The converter is brand new. I changed the lockup to 70mph today and took it out on the highway and it thew another DTC 68, which is a slip error. :-/ It disabled 4th gear along with it as well. Clearing the codes makes it work again..



Thanks man.. I'm thinking its either the converter is jacked up or the TCC valve/circuit in the valve body is worn out. The problem is I don't know how to test either one! lol



I think the stock converter size is something like 13". I know going to a 10" converter is significantly less lockup surface apply area.

If I swap the old one back in and it doesn't happen, I'm thinking it could still be a possibility that the TCC valve could be worn out just enough to work w/the old one, but struggle applying lockup to the PTC 10" one.


Do you guys think swapping back in the stock converter would lead to any conclusive results? Or should I just send back the PTC converter to be inspected? Thanks again guys!

 

i had my stock 4l80e converter restalled a couple years ago and it actually worked very well with my 600 lift cam in my 461 big block..... i then went with a Revmax billet 3400 10.5" and havent looked back. my new stall converter is very solid when it locks up and is smooth as silk cruising. the stock restalled unit worked just aswell.

if shipping wasnt so high, id send my stock restalled converter your way and let you swap it out and give'r hell and see if that solves your problem and then we'd know for sure....

Jamie

 

Wtf tuning issue or what? - YouTube

This is what was happening on my truck. Message me if this is what is going on. I'll tell ya how to fix, it's not in tune it's in valve body if so.

 

Alright so against my better judgement I took it to a locally owned trans shop here. At first it seemed like they didn't want to help as I got the "3500 is way to big of stall for the street" story.. haha

Then they tried to say that my cruise/lockup speed had to be above 3500 or it will do that -- which I know is NOT correct. This is what I get though for bringing something there that isn't cookie cutter. lol

Anyway after talking to them for about an hour, I told them I need to eliminate variables and see if the problem is in the trans or in the converter. We agreed on installing a HD2 shift kit and AFL valve fix at minimum and once they had the pan off they would have a better idea...Maybe.. :-D

The dipstick indicates the color of the fluid looks good, so I'm thinking the problem is in the trans/valve body somewhere.

I'm going to keep this thread updated until this issue is fixed as I came across at least 20 other threads here where guys have had the same issue, but the solution is never posted (or found). Thanks again guys for the ideas..keep them coming..

 

There is a tsb out for the issue. On 60/80e in stock form they can have erratic tcc lock up. When you raise the line pressure it flutters the lock up in the converter on engagement basically it has a hydraulic leak in the valve body causing the issue. If you backed line pressure off it would probly be fine but your shifts would be terrible. Like it's backwards as it should be.

The tcc solonoid has a sealing oring on it start there to check that. If oring is good proceed to removing valve body then remove the valves pertaining tcc. Google search/ or all data DIY will be a big help here as to which ones. Sonnex makes problem solvers for this issue. And requires a special reemer to resize the bore in the valve body for the new pieces. Also check valve body for cracks replace if needed pretty unlikely tho. I ones you my number if you have questions.

 

Thanks again for the info Jeff!


Also, does anyone know a reputable transmission shop close to Orlando, FL? The shop I took it to looked at me like I had 3 heads when I told them I wanted the TCC valve, bored and re-sleeved.