[XJ wit an LT1]

ok the scoop is i was driving out to indiana, the tcase chain snapped hosing the tcase... got the rig taken apart , put a 4.3 atlas 2 in. now the trans has a slow leak that isnt coming from where the tcase bolts up to the trans.. its on the top somewhere put i can't find it. that isnt the real issue.. now mind you the trans was shifting PERFECTLY before this all started. now.. the trans will not shift out of 1st gear unless i gun it to 20 mph , let off the gas, then get back on it.. then it shifts thru the gears perfectly. if i stay on the gas it will just redline and not shift. so far i have tried replacing the tps, adjusted the vss, replaced one of the shift solenoids to no avail. no change at all. the only thing i have noticed is that the motor idles much better with the vss unplugged. HELP! i need to get the heep mobile and running right.

the running gear is a stock LT1 , 4l60e and atlas 2.

TIA for any help.

 

[XJ wit an LT1]

no one knows ANYTHING about these transmissions at all?

 

[odgreen]

Is the VSS sensor still on the transfer case tailshaft using the 40 tooth gear? VSS is required for proper operation of the PCM and the PCM has no way of controlling line pressure or shift points without it.

 

[raymo]

possible 4l60e answer

This is arguably one of the more problematic autos used in chevy's. The one in my wife's suburban died after about 50K miles. When it was being replaced (under warranty) the guy at the dealer said they fail all the time. He thought it was a super light duty tranny that belonged in something like an s10, not suburbans, etc and he thought it had no business towing anything. There is a tranny shop out near Barstow called 'Freeway Transmission' that knows what parts to swap in from a bling escalade that beefs up the clutches considerably. I don't have a number, but if you are rebuilding, you might at well replace with better parts.

That being said, the leak could be that it was overfilled?? It can leak out the vent if overfilled when it heats up. The shifting problem doesn't sound promising.....

 

[XJ wit an LT1]

i thought it might be overfilled as well but it isnt... there is no fluid coming from the vent tube or cooler lines. the vss is in an adapter kit from advanced adapters.

i'm thinking the trans is bitched.. even tho it was rebuilt a little more than a year ago. a buddy of mine has a 700r4 with kevlar clutches i may consider swapping in and having howell reprogram the computer.

or if anyone knows of a beefier tranny i may want to consider swapping in please toss that out as well.

if anyone has any other suggestions please fire them out. again i appreciate the responses.

 

[odgreen]

So are you not running the stock PCM then? It does not sound mechanical, tranny will not shift without the PCM telling it to. If you look at the stats GM tranny's are the most reliable domestic tranny made today, chrysler being worst, everyone has a horror story about something.

 

[XJ wit an LT1]

nothing changed with the pcm though.. it feels as if it's " catching " when i let off the gas and get back on it.. maybe its the torque converter?

 

[souldoubt]

4l60

Hey, did you make it to Indiana? I live in Indy and Im a gm tranny tech.

 

[odgreen]

Well you got two choices,

1. when the transfer case went it also took something in the tranny with it.

2. the vss signal is not correct/bad/missing, this will cause the tranny to not shift properly. I know nothing of the AA kit.


You talk about installing a 700R4, the 700R4 and 4L60E are virtually identical, 4L60E has a different valve body which is completely controlled by the PCM.

 

[XJ wit an LT1]

soul, i made it to indiana.. stayed for 2 months.. hated it and came back to jersey....


od ... from what i have been told the vss only controls overdrive... is this correct? if its not i'll go buy a new one tomorrow from the chevy dealer and give it a go.


the AA kit houses the reluctor ring and vss... it bolts in between the trans and tcase and thats all i really know about it.

 

[odgreen]

The only way the PCM knows how fast your going is by the VSS signal, since the PCM does all of the tranny functions (shifting, etc, not just overdrive) it cannot shift the tranny if it doesn't know how fast it's going. Curious, what kind of speedo do you have? if electronic it also should come from the VSS signal. Is your speedo correct? FYI getting VSS signal from the tranny instead of the transfer case output shaft will throw everything off when your in 4-low not that it matters too much.

Not saying that when the transfer case went it didn't take the tranny with it, just doesn't sound like it did.

 

[XJ wit an LT1]

the speedo is mechanical .. coming off the housing on the atlas.

hmm well i guess i'll go to the dealer and get a new VSS and try that... i did notice that the idle is much smoother with the VSS totally unplugged....

as for the low range deal i never had an issue with it in low range before .... do you think the change from a chain driven tcase to a gear driven tcase changed the dynamics of the load on the trans at all? i'm grabbing at straws because nothing has worked so far ....

 

[XJ wit an LT1]

any chance this could be like a torque converter lockup solenoid?

 

[odgreen]

the speedo is mechanical .. coming off the housing on the atlas.

How were you getting the speedo before the atlas?

hmm well i guess i'll go to the dealer and get a new VSS and try that... i did notice that the idle is much smoother with the VSS totally unplugged....

Dealer will probably want $80, get what you need from a parts store or gmpartsdirect.com, never the dealer.

The VSS has influence on the idle speed on some GM PCM/ECMs, don't know about this one.

as for the low range deal i never had an issue with it in low range before

Most don't go over 30 mph in low anyways so no big deal, now are we talking this all has happened right after your problem/atlas change or is just now starting to happen. Know nothing about the AA kit, does the sensor just screw all the way in like it did on the old transfer case or does it need to be adjusted somehow, i also assume it's actually a GM VSS sensor of the same type.

do you think the change from a chain driven tcase to a gear driven tcase changed the dynamics of the load on the trans at all? i'm grabbing at straws because nothing has worked so far ....

No

Just hoping you don't have to tear into the tranny, if that's what has to happen if you have the skills the parts only cost $100 or so for everything.

 

[XJ wit an LT1]

How were you getting the speedo before the atlas?
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From the back of the 231



Dealer will probably want $80, get what you need from a parts store or gmpartsdirect.com, never the dealer.

The VSS has influence on the idle speed on some GM PCM/ECMs, don't know about this one.

_______________________________________

The motor and trans are out of a 95 caprice ... The pcm/ecm is programmed as a 95 camaro with a 5.7 and 4L60e



Most don't go over 30 mph in low anyways so no big deal, now are we talking this all has happened right after your problem/atlas change or is just now starting to happen. Know nothing about the AA kit, does the sensor just screw all the way in like it did on the old transfer case or does it need to be adjusted somehow, i also assume it's actually a GM VSS sensor of the same type.
_________________________________________

The problem occured immediately after the np231 blow up / atlas install... never before



The AA kit has the vss that screws all the way in like the old tcase. i am unaware of any adjustment that needs to be made for it.




Just hoping you don't have to tear into the tranny, if that's what has to happen if you have the skills the parts only cost $100 or so for everything.
_________________________

If the tranny needs to be torn down its gonna cost me, because while i feel i am pretty good with a wrench i have never dabbled into the internals of a trans nor would i feel confident doing it for the first time in this case.

 

[odgreen]

Ok, so you used to have a electronic speedo and now have a mechanical one. There should have been no reason to change this if the current VSS is correct.

I'm still saying it's VSS/PCM related and not mechanical, can you point me to a place that discusses the AA kit, i tried to search for it and found nothing, assume someone very much in the know about GM PCM's sold you this so that it's correct. A call to AA might be in order to clear all that up. Hope this was all helpfull in figuring out your issues, would hate to steer you wrong.

 

[XJ wit an LT1]

the adapter from AA was ont here before the problem started to mate the 4l60e to the np231... it was just reused when i got the atlas... i am gonna give AA a call tomorrow and see if they have heard of this problem.. i have to call anyway to get the gm part number for the VSS ... thats for the help i will let you know how it turns out.