4L80E accumulator valve spring=harsh shifts?
07-03-2010, 11:47 PM
#1
4L80E accumulator valve spring=harsh shifts? Is the accumulator valve spring in the valve body vehicle specific?
I have a 1998 4L80E that has always shifted very harsh in all gears.
I got it with 60,000 miles on it and tore it down because it had no reverse. Everything looked good so I put it back together with new sealing rings and gaskets. The rev servo pin was too short causing the piston to hit the case and got a crack around the case side of the o ring groove. I replaced the piston and pin, and also installed a sonnax pressure limiting boost valve. It works fine except for the hard shifts. I've been running it like this for 30,000+ miles and it's dead on consistant.
This did come out of a 3500 HD and it had a brake on the tail housing.
Now it's in a 3/4 ton. The pressures are normal acording to the tech info on Transgo's site.
Would a transgo SK help? Not the HD kit but the one in the small box.
Thanks.
I have a 1998 4L80E that has always shifted very harsh in all gears.
I got it with 60,000 miles on it and tore it down because it had no reverse. Everything looked good so I put it back together with new sealing rings and gaskets. The rev servo pin was too short causing the piston to hit the case and got a crack around the case side of the o ring groove. I replaced the piston and pin, and also installed a sonnax pressure limiting boost valve. It works fine except for the hard shifts. I've been running it like this for 30,000+ miles and it's dead on consistant.
This did come out of a 3500 HD and it had a brake on the tail housing.
Now it's in a 3/4 ton. The pressures are normal acording to the tech info on Transgo's site.
Would a transgo SK help? Not the HD kit but the one in the small box.
Thanks.
07-05-2010, 12:20 AM
#2
There is a different accumulator spring for each shift as well as an accumulator valve spring in the VB.
I doubt you have an accumulator problem. You may have excessive line pressure.
I would put a gauge on it and see what the pressures are.
Someone may have cranked up the pressure control solenoid or you may have another sensor issue or PR valve issue.
I doubt you have an accumulator problem. You may have excessive line pressure.
I would put a gauge on it and see what the pressures are.
Someone may have cranked up the pressure control solenoid or you may have another sensor issue or PR valve issue.
07-05-2010, 08:42 AM
#3
As Jake said you need to see what the pressures are with a gauge to verify what is going on. The only thing that might be and issue other than the PCS would be a sticky accumulator valve in the valve body. I do know with the shift kits I have installed the lighter the tension on this valve the firmer the shifts. Are you currently running a shift kit? Also one thing I ran into a bunch of years ago, if you leave check ***** out of this unit it will shift very hard!
07-05-2010, 10:32 AM
#4
I did check pressures.
It has no shift kit.
It did come out of a heavier truck than it's in now.
It has a sonnax pressure limiting boost valve.
I've had it apart several times, everything looks normal.
In reading the instructions on the transgo kit (on their site) I starting thinking about the accumulator valve in the valve body.
Was wondering if the accumulator valve springs had the same effect in a 4L80E as it does in say a 700.
The pressures are normal acording to the tech info on Transgo's site.
It did come out of a heavier truck than it's in now.
It has a sonnax pressure limiting boost valve.
I've had it apart several times, everything looks normal.
In reading the instructions on the transgo kit (on their site) I starting thinking about the accumulator valve in the valve body.
Was wondering if the accumulator valve springs had the same effect in a 4L80E as it does in say a 700.
07-05-2010, 11:04 AM
#5
The pressures could be in a "normal range" but not at the proper time.
Max line on a stock unit is usually about 170 psi, minimum will be about 60. If it spikes or has more than 60 minimum it will shift hard.
i.e. if someone has cranked up the PCS. There would be nothing visible to show this and the max pressures wouldn't change, but the pressures less than max would all be higher.
Max line on a stock unit is usually about 170 psi, minimum will be about 60. If it spikes or has more than 60 minimum it will shift hard.
i.e. if someone has cranked up the PCS. There would be nothing visible to show this and the max pressures wouldn't change, but the pressures less than max would all be higher.
07-05-2010, 11:20 AM
#6
I'll have to check again because I didn't write anything down. I had the test procedure written down and just looked at that and everything checked out as it should according to the papers.
So there are no differences between a 3500 HD tow truck calibration and a van?
It shifts perfect when it's fully loaded towing a car on a trailer.
I'll get out there and test again and write things down, it's time for a fluid change so I was planning on looking into this while the pan was off.
Thanks for the help.
So there are no differences between a 3500 HD tow truck calibration and a van?
It shifts perfect when it's fully loaded towing a car on a trailer.
I'll get out there and test again and write things down, it's time for a fluid change so I was planning on looking into this while the pan was off.
Thanks for the help.
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07-05-2010, 01:17 PM
#8
Ok, it looks like theres a problem.
Pressure test now get these numbers.
Idle 100 psi
Reverse is 70 and goes to 300 by 1/8 throttle.
Stopped in Drive stays at 100 psi until I tap the gas, then it'll go to 45 psi.
With Drive at 45 psi, it will go up to 200 psi then shift 1-2 then go to 125 psi and stay there through all shifts, lock up and cruise at 50 mph (as fast as I went)
WOT it goes to 150 psi.
Pressure test now get these numbers.
Idle 100 psi
Reverse is 70 and goes to 300 by 1/8 throttle.
Stopped in Drive stays at 100 psi until I tap the gas, then it'll go to 45 psi.
With Drive at 45 psi, it will go up to 200 psi then shift 1-2 then go to 125 psi and stay there through all shifts, lock up and cruise at 50 mph (as fast as I went)
WOT it goes to 150 psi.
07-05-2010, 02:03 PM
#9
Reverse pressures look OK.
100 psi at idle is excessive for electronic control. That is about what a 4L80E will put out with fixed line pressure at idle, and then it will spike to 160-180 psi when you give it some rpm for pump volume.
I'm not sure why yours is dropping when you give it throttle. I would look at the TPS readings with a scanner, you might have a dead spot at idle on the TPS causing the PCM to command max line?
I would probably try a new PCS if the TPS readings all look good.
100 psi at idle is excessive for electronic control. That is about what a 4L80E will put out with fixed line pressure at idle, and then it will spike to 160-180 psi when you give it some rpm for pump volume.
I'm not sure why yours is dropping when you give it throttle. I would look at the TPS readings with a scanner, you might have a dead spot at idle on the TPS causing the PCM to command max line?
I would probably try a new PCS if the TPS readings all look good.
07-05-2010, 02:41 PM
#10
Been looking at it.
My scanner, TunerPro RT, shows good TPS movement (it's not very old)
I'm going to replace the PCS. It seems like it's sticking. One other thing I did was start it up, pressure stays at 100-110 psi Unless I either tap the gas OR put it in manual 1st.
I can pull it down 3, 2, steady 100-110, at 1st it goes to 125 psi.
Then back up 2, 3, OD it stays at 45 psi.
When it was apart I did put solid rings on everything IIRC, I hear this is not the best thing.
My scanner, TunerPro RT, shows good TPS movement (it's not very old)
I'm going to replace the PCS. It seems like it's sticking. One other thing I did was start it up, pressure stays at 100-110 psi Unless I either tap the gas OR put it in manual 1st.
I can pull it down 3, 2, steady 100-110, at 1st it goes to 125 psi.
Then back up 2, 3, OD it stays at 45 psi.
When it was apart I did put solid rings on everything IIRC, I hear this is not the best thing.
07-05-2010, 04:05 PM
#11
Well I found some bad news.
That Sonnax boost valve sleeve has a ridge around it and the piston catches it slightly.
This only has 30,000 miles on it at the most.
The other bad news is that it's not the pressure limiting valve that I ordered back in '05.
This is just the o-ring style, I see the confusion, one part # ends in 01k and one ends in 10k. (I should have seen the difference back then)
I think I'm going to get the transgo kit, the SK-4L80E in the small box.
Anyone on here sell the transgo kit?
That Sonnax boost valve sleeve has a ridge around it and the piston catches it slightly.
This only has 30,000 miles on it at the most.
The other bad news is that it's not the pressure limiting valve that I ordered back in '05.
This is just the o-ring style, I see the confusion, one part # ends in 01k and one ends in 10k. (I should have seen the difference back then)
I think I'm going to get the transgo kit, the SK-4L80E in the small box.
Anyone on here sell the transgo kit?
Last edited by Jays_SSZ28; 01-30-2018 at 08:02 PM.
07-05-2010, 04:16 PM
#12
That's likely the issue.
I use the Sonnax valve often so I'll keep an eye on any that come in for wear.
The TransGo boost valve is a nice piece as well but it's not sold seperately of the kit AFAIK and I don't use most of the kit. Some unnecessary mods IMO.
FLT may be able to get you the SK?
I use the Sonnax valve often so I'll keep an eye on any that come in for wear.
The TransGo boost valve is a nice piece as well but it's not sold seperately of the kit AFAIK and I don't use most of the kit. Some unnecessary mods IMO.
FLT may be able to get you the SK?
