Fluid Starvation Issue? 4L80
09-25-2010, 10:19 AM
#1
Fluid Starvation Issue? 4L80 I've got a manual valvebody 4L80 with the transgo 3 shift kit in my Turbo '98 TA. I took it to the track last night for a couple of test passes. Before going out to the track, I hadn't launched the car from a deadstop - just from 2nd gear rolls and 1st gear rolls from around 10-20 mph. Car is making around 500rwhp/520rwtq through the 4L80 unlocked.
When I got to the track, I let the car cool for a few minutes, went to tech in and got lined up for my first pass. After the burnout the trans temp was at 200. Put the car in 1, launched, car hooked and when boost hit a few feet out it hazed the tires, I peddled it a bit, and got back in it, shifted 1-2 and it felt like the car was still spinning the tires for a second til I realized that it was at 6500rpm and not holding power in 2nd or when I'd shift it to 3rd. I coasted it to the end of the track and around the return road and parked it. At the time I figured that I toasted the converter because the trans would still shift, but I had no pressure in the converter to push the car (so it felt)...and the trans temp had fallen from 200 to 187 by the end of the run.
I let the car sit for about 45 minutes, inspecting it for leaks etc. All looked good. Hopped back in it and fired it up and put it in 1st. It idled forward fine. Took it for a spin around the pits and shifted to 2nd, felt fine. Took it out on the road by the track and it felt totally normal so I drove it home. When I got close to home I hit it at about 3k rpm in 2nd gear and it ran perfect.
The trans has a stock shallow truck pan on it and new filter. It has the long (36" I think) Lokar dipstick that we all know can be deceiving unless you fill it and let it sit for a while to get an accurate reading on the stick. Level is right on according to the stick. I've heard of guys with 4L60s having problems with fluid slosh on launch, starving the pump and causing them to hit the rev limiter on the 1-2 shift. Think that maybe I have a similar issue and a deep pan would be a good idea? Any other suggestions?
The only other similar thing that I've noticed before is when the car is up on ramps (front end only) and I leave it for a day and pull it off to drive it, it does this similar thing where it feels like the converter isnt engaging and its partway slipping in all gears til I drive it for a bit and it goes back to normal.
When I got to the track, I let the car cool for a few minutes, went to tech in and got lined up for my first pass. After the burnout the trans temp was at 200. Put the car in 1, launched, car hooked and when boost hit a few feet out it hazed the tires, I peddled it a bit, and got back in it, shifted 1-2 and it felt like the car was still spinning the tires for a second til I realized that it was at 6500rpm and not holding power in 2nd or when I'd shift it to 3rd. I coasted it to the end of the track and around the return road and parked it. At the time I figured that I toasted the converter because the trans would still shift, but I had no pressure in the converter to push the car (so it felt)...and the trans temp had fallen from 200 to 187 by the end of the run.
I let the car sit for about 45 minutes, inspecting it for leaks etc. All looked good. Hopped back in it and fired it up and put it in 1st. It idled forward fine. Took it for a spin around the pits and shifted to 2nd, felt fine. Took it out on the road by the track and it felt totally normal so I drove it home. When I got close to home I hit it at about 3k rpm in 2nd gear and it ran perfect.
The trans has a stock shallow truck pan on it and new filter. It has the long (36" I think) Lokar dipstick that we all know can be deceiving unless you fill it and let it sit for a while to get an accurate reading on the stick. Level is right on according to the stick. I've heard of guys with 4L60s having problems with fluid slosh on launch, starving the pump and causing them to hit the rev limiter on the 1-2 shift. Think that maybe I have a similar issue and a deep pan would be a good idea? Any other suggestions?
The only other similar thing that I've noticed before is when the car is up on ramps (front end only) and I leave it for a day and pull it off to drive it, it does this similar thing where it feels like the converter isnt engaging and its partway slipping in all gears til I drive it for a bit and it goes back to normal.
09-25-2010, 03:04 PM
#3
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Attach a gauge to see if line pressure is dropping when u launch.
The condition you describe when it sits sounds like converter drain back. Check your dipstick before you start it after it has sat for a few days to see if its way over filled to confirm. Several things can cause this.
If line pressure drops on the launch, I would remove the pan & inspect-replace the filter. Check the seal in the case also.
While the pan is off-mark the pan rail edge to the dipstick. That should be your full level on your pos dipstick.
Lastly, where is your temp sender located? I would expect to see temp spikes above 200 in a outgoing cooler line.
In the pan, you want to keep the temps under 200. You may need additional cooling.
The condition you describe when it sits sounds like converter drain back. Check your dipstick before you start it after it has sat for a few days to see if its way over filled to confirm. Several things can cause this.
If line pressure drops on the launch, I would remove the pan & inspect-replace the filter. Check the seal in the case also.
While the pan is off-mark the pan rail edge to the dipstick. That should be your full level on your pos dipstick.
Lastly, where is your temp sender located? I would expect to see temp spikes above 200 in a outgoing cooler line.
In the pan, you want to keep the temps under 200. You may need additional cooling.
09-25-2010, 05:45 PM
#5
Attach a gauge to see if line pressure is dropping when u launch.
The condition you describe when it sits sounds like converter drain back. Check your dipstick before you start it after it has sat for a few days to see if its way over filled to confirm. Several things can cause this.
If line pressure drops on the launch, I would remove the pan & inspect-replace the filter. Check the seal in the case also.
While the pan is off-mark the pan rail edge to the dipstick. That should be your full level on your pos dipstick.
Lastly, where is your temp sender located? I would expect to see temp spikes above 200 in a outgoing cooler line.
In the pan, you want to keep the temps under 200. You may need additional cooling.
The condition you describe when it sits sounds like converter drain back. Check your dipstick before you start it after it has sat for a few days to see if its way over filled to confirm. Several things can cause this.
If line pressure drops on the launch, I would remove the pan & inspect-replace the filter. Check the seal in the case also.
While the pan is off-mark the pan rail edge to the dipstick. That should be your full level on your pos dipstick.
Lastly, where is your temp sender located? I would expect to see temp spikes above 200 in a outgoing cooler line.
In the pan, you want to keep the temps under 200. You may need additional cooling.
The trans has the big b&m 11x11x1.5 cooler on it up in front of the airdam on the pass side kinda dope style. I have a theory about the heat in the trans. The temp sender is in the factory drain plug location on the bottom outside edge on the drivers side. The crossover on the turbo kit runs down along and right behind the trans and isn't coated. I've noticed the temps being steady while the cars moving and climb when it's sitting still. I'm wondering if it's measuring case/pan temp and not the actual fluid. I plan on wrapping the crossover soon to see if that helps.
I'm wondering the same thing. I'll disconnect it sometime this weekend and try launching it again and see how it acts.
09-25-2010, 09:07 PM
#6
Did some more research about vacuum modulator and these trannys with boost, sounds like I need to invest in a transgo VBP-VAC, sounds like a 3 way checkvalve? Does this just install where the vacuum line is T'd into vacuum source currently?
09-25-2010, 10:06 PM
#7
The problem you are having is not likely fluid starvation.
I do suggest checking the dipstick calibration but I've seen this issue on the TransGo -3 equipped 4L80Es and it's the major reason we designed our own full manual setup.
I think a pressure gauge will show steady pressure from launch, the 4l80E doesn't get into issues at your level IME.
I have "fixed" this issue on several TransGo -3 units but I prefer other methods over the fix.
I do suggest checking the dipstick calibration but I've seen this issue on the TransGo -3 equipped 4L80Es and it's the major reason we designed our own full manual setup.
I think a pressure gauge will show steady pressure from launch, the 4l80E doesn't get into issues at your level IME.
I have "fixed" this issue on several TransGo -3 units but I prefer other methods over the fix.
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09-25-2010, 10:43 PM
#8
The problem you are having is not likely fluid starvation.
I do suggest checking the dipstick calibration but I've seen this issue on the TransGo -3 equipped 4L80Es and it's the major reason we designed our own full manual setup.
I think a pressure gauge will show steady pressure from launch, the 4l80E doesn't get into issues at your level IME.
I have "fixed" this issue on several TransGo -3 units but I prefer other methods over the fix.
I do suggest checking the dipstick calibration but I've seen this issue on the TransGo -3 equipped 4L80Es and it's the major reason we designed our own full manual setup.
I think a pressure gauge will show steady pressure from launch, the 4l80E doesn't get into issues at your level IME.
I have "fixed" this issue on several TransGo -3 units but I prefer other methods over the fix.
09-26-2010, 02:30 AM
#9
Maybe I'm misunderstanding your symptoms but with the TG-3 kit here is what I've seen.
Delayed 2-3.
No 1-2 shift at WOT warm, or a return to 1st during heavy throttle in 2nd gear, which is oftentimes mistaken for slippage because it seems to free rev.
Delayed 2-3 is easy to improve and almost eliminate. It is a fluid volume and circuit restriction issue, it requires several changes but nothing complex.
The 1-2 shift issue is USUALLY fixable but it seems to be pressure (too much) related and requires changing a shift valve spring, fixing a crossleak problem, enlarging some fluid path, timing the manual valve, and sprinkling chicken blood while chanting.
Delayed 2-3.
No 1-2 shift at WOT warm, or a return to 1st during heavy throttle in 2nd gear, which is oftentimes mistaken for slippage because it seems to free rev.
Delayed 2-3 is easy to improve and almost eliminate. It is a fluid volume and circuit restriction issue, it requires several changes but nothing complex.
The 1-2 shift issue is USUALLY fixable but it seems to be pressure (too much) related and requires changing a shift valve spring, fixing a crossleak problem, enlarging some fluid path, timing the manual valve, and sprinkling chicken blood while chanting.
09-26-2010, 09:43 AM
#11
i didnt have a ton of suc. with the HD-3 kit, i replaced it with another VB and a trans controller, much better, lol
X3 on dipstick cal., i noticed when filling my trans, had a gauge to read doing this, the trans was still building pressure within a quart or 2 of being filled, so this tells me they gotta be filled accurate
X3 on dipstick cal., i noticed when filling my trans, had a gauge to read doing this, the trans was still building pressure within a quart or 2 of being filled, so this tells me they gotta be filled accurate
10-26-2010, 08:20 AM
#12
Just an update. I let the car sit for about 2 weeks without driving it, took it out and the converter felt fine and the car moved without feeling like it was spinning its wheels - so I guess I can rule out the possibility for converter drainback - at least when the cars level.
I installed the Transgo Vac/Boost Bypass Kit (little check valve that installs on the vacuum modulator line). The car seems to launch now and shift 1-2 and hold like it should. I'll get it out to the track on a sunday afternoon next month and see if I can get a clean pass out of it. Trans temps are running cooler due to cooler ambient temps lately too...which may be part of it as the Transgo shift kit has been rumored to cause issues when run hot.
Another issue the trans has had in the past, and still does it but not as noticeably as it was when the weather was warmer, is after I've been driving the car a while and the trans is up to operating temps and come to a stop the gauge tends to climb pretty excessively. I'm wondering if the hot exhaust crossover that wraps around the transmission is heating up the trans/pan/sensor enough to be the cause of this significant temperature increase. I'm going to install exhaust wrap on the crossover this weekend and see if that makes much of a difference to keep the trans temps down.
I installed the Transgo Vac/Boost Bypass Kit (little check valve that installs on the vacuum modulator line). The car seems to launch now and shift 1-2 and hold like it should. I'll get it out to the track on a sunday afternoon next month and see if I can get a clean pass out of it. Trans temps are running cooler due to cooler ambient temps lately too...which may be part of it as the Transgo shift kit has been rumored to cause issues when run hot.
Another issue the trans has had in the past, and still does it but not as noticeably as it was when the weather was warmer, is after I've been driving the car a while and the trans is up to operating temps and come to a stop the gauge tends to climb pretty excessively. I'm wondering if the hot exhaust crossover that wraps around the transmission is heating up the trans/pan/sensor enough to be the cause of this significant temperature increase. I'm going to install exhaust wrap on the crossover this weekend and see if that makes much of a difference to keep the trans temps down.
