Slipping or Torque Converter problem?
#11
10-12-2011, 03:58 PM
Saw this.
This is from one of the posts on there:
This is from one of the posts on there:
Off the top we’d say to let it shift as fast as possible with as much pressure as possible. Anything you can do to speed up the shift, or create more pressure while shifting is fine with me. It will reduce friction and lessen the heat build up inside the transmission it’ll allow the clutches to live longer.
When we dyno these units we spend a lot of time on the shift quality and speed.
You see it all the time won’t shift on 2-3 hits rev limiter, what we have to find out is weather or not it’s a slip or a miss shift A long engaging shift is normally a slipping clutch, a short shift into the limiter is a timing issue or tuning problem. These guys who say its neutral is normally a tuning issue, unless of coarse the clutch is totally gone.
When we dyno these units we spend a lot of time on the shift quality and speed.
You see it all the time won’t shift on 2-3 hits rev limiter, what we have to find out is weather or not it’s a slip or a miss shift A long engaging shift is normally a slipping clutch, a short shift into the limiter is a timing issue or tuning problem. These guys who say its neutral is normally a tuning issue, unless of coarse the clutch is totally gone.
#12
10-12-2011, 04:34 PM
Join Date: Oct 2007
Location: The 'Burbs of Chicago
Posts: 18,306
If your 4L60E has a vacuum modulator, then it's been modified.
I don't know if anybody other than TransGo makes it, but here it is: TransGo Vac Modulator Kit
See if you can find the instructions for it, to make sure it's set up correctly.
I don't know if anybody other than TransGo makes it, but here it is: TransGo Vac Modulator Kit
See if you can find the instructions for it, to make sure it's set up correctly.
#13
10-12-2011, 04:55 PM
I assume that it's on the other side of the trans just like on a TH400 and of course I don't have any pics of that side.
I looked at that kit above a little while ago when you and that link I referenced above talked about them. I don't remember there being a modulator but I could be wrong. It's raining here so I won't be able to look at it till tomorrow or the next day. I may just hook up the vacuum line from the trans to the rear of the manifold if I can do that quickly this evening without getting too wet.
#14
10-12-2011, 05:01 PM
Join Date: Oct 2007
Location: The 'Burbs of Chicago
Posts: 18,306
I assume that it's on the other side of the trans just like on a TH400 and of course I don't have any pics of that side.
I looked at that kit above a little while ago when you and that link I referenced above talked about them. I don't remember there being a modulator but I could be wrong. It's raining here so I won't be able to look at it till tomorrow or the next day. I may just hook up the vacuum line from the trans to the rear of the manifold if I can do that quickly this evening without getting too wet.
I looked at that kit above a little while ago when you and that link I referenced above talked about them. I don't remember there being a modulator but I could be wrong. It's raining here so I won't be able to look at it till tomorrow or the next day. I may just hook up the vacuum line from the trans to the rear of the manifold if I can do that quickly this evening without getting too wet.
#15
10-12-2011, 07:07 PM
I guess I meant to say that I would make sure that it's hooked up from when I pulled the harness for the cam sensor harness. I ended up having to extend that harness because the previous owner of the engine truly made a frankenstein. The cam and timing gear are from the LS2 out of the GTO apparently so the timing cover has the cam sensor in it. I had to extend the harness and flip the two outer wires for the LS2 cam sensor to work. I think I might have accidentally pulled the vacuum line loose earlier but now I don't think so.
I had my Predator with me at work and I increased the shift firmness pressure by 15 PSI. After reading that other link I posted and quoted I figured that maybe the pressure wasn't high enough to engage the lockup. At first I tried lowering it but that seemed to make it worse so I upped it. It got rid of the rpm going up and down at cruise and even made it feel like it had a bit more ummph.
The only problem now is that it still screams up to the rev limiter and doesn't shift but I'm trying to figure out if I'm in 3rd or not when that happens. I read that it won't shift into 4th at WOT but if I'm in third and floor it I would expect it to kick down into passing gear until it built up speed and then go back to third. So I dunno.
I had my Predator with me at work and I increased the shift firmness pressure by 15 PSI. After reading that other link I posted and quoted I figured that maybe the pressure wasn't high enough to engage the lockup. At first I tried lowering it but that seemed to make it worse so I upped it. It got rid of the rpm going up and down at cruise and even made it feel like it had a bit more ummph.
The only problem now is that it still screams up to the rev limiter and doesn't shift but I'm trying to figure out if I'm in 3rd or not when that happens. I read that it won't shift into 4th at WOT but if I'm in third and floor it I would expect it to kick down into passing gear until it built up speed and then go back to third. So I dunno.
#17
10-14-2011, 12:41 AM
Join Date: Oct 2007
Location: The 'Burbs of Chicago
Posts: 18,306
Looks like a busy vacuum hose. I'd try running a designated vacuum hose to the modulator if you can, just like the old school days.
You do understand what the vacuum modulator replaced (electronic pressure control solenoid), and what it does, and why it's important for it to work correctly?
You do understand what the vacuum modulator replaced (electronic pressure control solenoid), and what it does, and why it's important for it to work correctly?
#18
10-14-2011, 06:54 AM
I have limited knowledge of transmissions to be honest. I know that the modulator on the TH400 used engine vacuum to determine load for shifting. I had an adjustable one where I could raise or lower the shift points for it using an alan wrench. Other than that I do not know how it works. From what I just read in your post it sounds like as if it uses vacuum to control pressure in the valve body for shifting. That's just a guess at what you just stated.
#19
10-15-2011, 10:44 PM
Welp, transmission went out yesterday on the way home. I lost 3/4 gears and 1/2 are fine it seems. I was wondering if you could just replace the 3/4 clutches or if it's a full rebuild?
#20
10-16-2011, 12:56 AM
Join Date: Oct 2007
Location: The 'Burbs of Chicago
Posts: 18,306
Full rebuild. If the 3/4 clutches are toast, the forward clutches (beneath the 3/4's) probably are too. And who knows what else, till you get in there.
Had you been driving the car around with the vacuum modulator connected, or disconnected?
Had you been driving the car around with the vacuum modulator connected, or disconnected?
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