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Old 05-27-2013, 05:58 PM   #1
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Default 4L80E transgo hd2 Both blue springs or just one?

Doing a transgo HD2 kit here. It says "For slightly firmer shifts: Use outer BLUE Accum spring by itself. For even firmer shifts: use inner BLUE Accum spring by itself."

My question is how hard are these shifts? Anyone recommend one spring over the other? Or just use both?
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Old 05-27-2013, 06:53 PM   #2
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Default Re: 4L80E transgo hd2 Both blue springs or just one?

One must realize the 4L80E accumulator system was not designed for a passenger car but a truck. The more spring pressure outboard of the accumulator valve the softer the shifts shoud get ,but the firmer the 1-2 backoutshifts get.Damn ugly.If you are using this in a passenger car I suggest stopping the accumulator oil pressure from entering the rear servo by plugging it off.Then remove the 2 oil seal rings off the accumulato piston and permit 2nd oil to still enter the cavity but without going against accumulator oil pressure.The reason for this is so the trans does not lock up on a 2-1 manual downshift if the 1-2 shift valve cant exhaust faster than the low band applies or if the trans ever loses electric.Now use the 2nd gear feed orifice in the plate to fine tune the shift.Start with .085" and go larger as necessary. Remove the 3rd clutch checkball from the case and drill out the 4th feed to .085" as well and fine tune fron there.Block 3rd and 4th accumulators with a block off plate or by plugging the housing.If you are using a bleed hole in the 3rd clutch be sure to remove the reverse check ball in the case or there will be a delay going into reverse.
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Old 05-27-2013, 08:23 PM   #3
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Default Re: 4L80E transgo hd2 Both blue springs or just one?

Great info. Not that I have the capacity to know what the hell you just said. Lol.
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Old 05-27-2013, 08:38 PM   #4
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Default Re: 4L80E transgo hd2 Both blue springs or just one?

1 spring is not bad 2 springs is a pretty good bump.


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Old 05-28-2013, 07:26 PM   #5
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Default Re: 4L80E transgo hd2 Both blue springs or just one?

2 springs here with a nice "solid" shift.
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Old 05-28-2013, 07:30 PM   #6
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Default Re: 4L80E transgo hd2 Both blue springs or just one?

On the 4L80E the more spring pressure you have outboard of the valve the LOWER accumulator pressure is so the shifts should be lighter with 2 springs and they are ,but the backout shifts get bangier because of lack of rapid torque signal pressure drop off amongst other things.Weird.
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Old 05-29-2013, 04:55 PM   #7
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Default Re: 4L80E transgo hd2 Both blue springs or just one?

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Originally Posted by LS1NOVA View Post
2 springs here with a nice "solid" shift.
So you're pretty happy with the way it shifts with two springs?
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Old 05-29-2013, 06:55 PM   #8
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Default Re: 4L80E transgo hd2 Both blue springs or just one?

A little hydraulics lesson for a TH400 or 4L80E rear servo....

If you block the accumulator oil and omit the 1-2 accumulator piston seals, so that 2nd gear oil acts on the entire backside of the servo, the feed hole for 2nd needs to be much larger than stock.
It will CAUSE a 2-1 downshift bind because low gear or rear band apply oil will push on the servo, putting pressure on the 2nd gear circuit, temporarily keeping it charged.
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Old 05-29-2013, 08:19 PM   #9
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Default Re: 4L80E transgo hd2 Both blue springs or just one?

My method has worked for several years with no ill side effets.As the lever is pulled into lo gear ,oil will enter the low servo cavity but will not apply the servo until the shift solenoid "A" has released the shift valve and exhausted 2nd gear apply oil.Without the rings the oil pressure on both sides is equal but as 2nd oil exhausts the pressure drops on the spring side but the 2nd accumulator spring will keep low servo and band off until full exhaust is made.As far as the feed hole size,it is irrelevant because the checkball next to it is in the exhaust mode.This system was well thought out by GM and keeps the band off and the resultant bind up if the electric fails when shifting to manual low.They also designed a bypass into low servo in reverse if the shift valve gets stuck because it is on in Reverse.
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Old 05-29-2013, 08:33 PM   #10
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Default Re: 4L80E transgo hd2 Both blue springs or just one?

This advanced transmission talk can confuse a guy. I'm just going off the transgo instructions so far.
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Old 05-29-2013, 08:43 PM   #11
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Default Re: 4L80E transgo hd2 Both blue springs or just one?

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Originally Posted by chris718 View Post
My method has worked for several years with no ill side effets.As the lever is pulled into lo gear ,oil will enter the low servo cavity but will not apply the servo until the shift solenoid "A" has released the shift valve and exhausted 2nd gear apply oil.Without the rings the oil pressure on both sides is equal but as 2nd oil exhausts the pressure drops on the spring side but the 2nd accumulator spring will keep low servo and band off until full exhaust is made.As far as the feed hole size,it is irrelevant because the checkball next to it is in the exhaust mode.This system was well thought out by GM and keeps the band off and the resultant bind up if the electric fails when shifting to manual low.They also designed a bypass into low servo in reverse if the shift valve gets stuck because it is on in Reverse.
The feed hole needs to be bigger for any kind of decent apply. .085" would provide soft shifts. I would recommend .110" as a minimum for that setup in a performance combo but shift quality is subjective.

Band oil comes straight off the manual valve, so it doesn't care what position any shift valve is in, pressure is coming on quicker than 2nd can release. When the shift valve does move and release 2nd, as it is exhausting, low band apply is keeping it pressured up, because the piston is "chasing" it.

It's a little side effect I learned when sorting out a RMVB with engine braking.
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Old 05-29-2013, 09:06 PM   #12
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Default Re: 4L80E transgo hd2 Both blue springs or just one?

If this was true true,why does a stock trans not lock up in low?It still has acc oil and 2nd oil still on the spring side of the cavity, and at a much lower pressure so this would cause an even worst bind. Anyone interested in using my methods here and finds that they are incorrect ,let me know what your concerns are and I will walk you thru it. Your best bet is to follow the kit instructions and contact TRANSGO if you need to customize.What do I know about repairing television sets anyway?
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Old 05-29-2013, 10:05 PM   #13
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Default Re: 4L80E transgo hd2 Both blue springs or just one?

http://www.youtube.com/watch?v=yNjkmLoYax4
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Old 05-30-2013, 03:15 AM   #14
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Default Re: 4L80E transgo hd2 Both blue springs or just one?

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Originally Posted by chris718 View Post
If this was true true,why does a stock trans not lock up in low?It still has acc oil and 2nd oil still on the spring side of the cavity, and at a much lower pressure so this would cause an even worst bind.
When you downshift to manual low, accumulator oil becomes the same as apply or line pressure on a TH400 or 4L80E.

This accumulator pressure, the spring pressure, and the circuits being seperated are what helps the bind up. There isn't as great of a volume of 2nd gear oil on the back of the servo that has to be exhausted out of 2nd gear. A large(r) volume of oil is now accumulator oil.
So the 2nd oil being chased out of the backside of the servo is reduced, and also has another circuit to prevent it being the one "pushed" as much.

Killing the accum oil to the back of the servo, and omitting the sealing rings causing 2nd gear oil to cover the back of the servo will work fine on many applications, but it has a large effect on the 1-2 upshift quality, and servo/band clearance becomes more critical to this shift quality.

I've noticed a slight 2-1 bind on units with all circuits intact on the dyno. Slightly more pronounced bind with accumulator oil blocked and 2nd oil flooding the back.
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Old 10-24-2016, 04:58 AM   #15
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Default Re: 4L80E transgo hd2 Both blue springs or just one?

Quote:
Originally Posted by chris718 View Post
One must realize the 4L80E accumulator system was not designed for a passenger car but a truck. The more spring pressure outboard of the accumulator valve the softer the shifts shoud get ,but the firmer the 1-2 backoutshifts get.Damn ugly.If you are using this in a passenger car I suggest stopping the accumulator oil pressure from entering the rear servo by plugging it off.Then remove the 2 oil seal rings off the accumulato piston and permit 2nd oil to still enter the cavity but without going against accumulator oil pressure.The reason for this is so the trans does not lock up on a 2-1 manual downshift if the 1-2 shift valve cant exhaust faster than the low band applies or if the trans ever loses electric.Now use the 2nd gear feed orifice in the plate to fine tune the shift.Start with .085" and go larger as necessary. Remove the 3rd clutch checkball from the case and drill out the 4th feed to .085" as well and fine tune fron there.Block 3rd and 4th accumulators with a block off plate or by plugging the housing.If you are using a bleed hole in the 3rd clutch be sure to remove the reverse check ball in the case or there will be a delay going into reverse.
Thanks, that makes a lot of sense.
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