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Author Topic: 4L60E; Shift problems after complete rebuild  (Read 3271 times)

Offline dragula07

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4L60E; Shift problems after complete rebuild
« on: May 15, 2008, 01:47:24 PM »
Newbie here, but long time lurker.     ;D

I have a friend with a '96 Impala SS (LT1/5. 7L) that I rebuilt the transmission in.  

He races this car pretty often.    It actually has a stroked LT1 in it (with cam, heads, headers, etc.   ).    His old trans was trashed; clutches were shot, apply piston seals were blown, shell collar was broken off, etc.  

We built the trans with the new beast shell, kevlar band, shift reprogramming kit, corvette servo, hd clutches, and a few other upgrades.    It also has a new 3200rpm stall convertor.   

The transmission shifts fine under normal driving except that it shifts from 1-2 a little too soon.   

But of more concern is that at wide open throttle it won't shift from 2-3rd at all.    He carries it to about 6500rpms and then lets off.  

I had a trans pressure gauge but I loaned it out and it never found it's way back home.    >:(  So, this morning I just ordered a new one from ebay.    My point being that I haven't checked the lines pressures yet.  

His ECM has also had some custom work done to it and he has an appointment next week to have it dyno tuned.   

I'm curious as to what I should look for that would cause these problems? I know that normally the 3rd clutches would be of concern but they're all new along with pretty much everything in the trans.    Could it be something in the ECM causing this?

Thanks for any help!

« Last Edit: May 15, 2008, 01:49:24 PM by dragula07 »

Offline crunch

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Re: 4L60E; Shift problems after complete rebuild
« Reply #1 on: May 15, 2008, 08:19:04 PM »
When you start modifying stuff that is what you get into. :ROFL

How much and how was the PCM modified?
How much was the valve body modified?

Forum rules do not let us get into modified stuff
You are on you own with that one.
If you want to put it back to stock we might be able to help.
Crunch
« Last Edit: May 15, 2008, 08:20:06 PM by crunch »
OEM parts only hurt one time Crunch said that.
Cheap after market stuff will bite you many times. My brother in law is learning that the hard way.

Offline dragula07

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Re: 4L60E; Shift problems after complete rebuild
« Reply #2 on: May 15, 2008, 08:43:22 PM »
Quote from: crunch link=topic=6219.  msg35320#msg35320 date=1210900744

Forum rules do not let us get into modified stuff
You are on you own with that one. 


I didn't know that.   Sorry.    :-[

I don't know what's been done to the PCM.   I wasn't involved with that.  

The only thing done to the valve body was the typical GM reprogramming kit.    

Hmmmm, without getting into modified stuff I'm not sure how to proceed with my info.    :-\

I guess the simplest thing is how likely do you think that it's an internal trans problem as opposed to an electronic issue? I assume that since the PCM basically tells the trans when to shift, that's it probably a problem there? Is this adjustable within the PCM?
« Last Edit: May 15, 2008, 08:48:50 PM by dragula07 »

Offline Transman

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Re: 4L60E; Shift problems after complete rebuild
« Reply #3 on: May 15, 2008, 09:13:50 PM »
The pointer I would lead you to is see what the TPS is doing. If the pcm was reprogrammed, the settings were likely changed adding the changes to the trans (stall speed) the pcm is probably confused as the the shift points. I think your problem is most likely electrical in some fashion due to the changes. That probably won't narrow the cause down much but if it shifts fine on normal throttle and refuses to shift on full throttle then it is in "control" (pcm, tps, maf, poor grounds or connections, etc). Look there first, Transman
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Offline dragula07

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Re: 4L60E; Shift problems after complete rebuild
« Reply #4 on: May 22, 2008, 07:00:16 PM »
Just thought I would add an update that he had the PCM/ECM professionally "retuned" the other night and he said that it shifts perfectly now.  1-2 shift at 17mph under normal driving and 6200rpm shifts at WOT.  He said it will even bark second gear.   ;D

Thanks for the help guys!

Offline Transman

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Re: 4L60E; Shift problems after complete rebuild
« Reply #5 on: May 23, 2008, 07:26:37 PM »
Glad it's fixed and thanks for the update, Transman
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