Guys I am installing an HD2 kit, just wondering if there are any deviances you would recommend?
This is a temporary trans until I can get with Franks Custom Trans for a full build, I am hoping later this year. I’m only saying that so nobody says “thats not gonna last very long for you”. I basically need to get this vehicle on the road and get a BUNCH of other things ironed out in the meantime. I have changed ALOT in this vehicles powertrain. And do some learning.

2006 GMC Envoy, 4x4, 3.73 gears. Has 285/45/20’s with a 4” lift. Weighs about 4800-5000 lbs. I rebuilt a 4.8 and added a s369, BTR tork cam, injectors 12613412 from BMZ on Ebay, new but stock fuel pump. I have read it will supply up to 500hp. It has a 2800 stall.

The trans is in great shape, everything worked great, it shifted great before, no flares or anything.
I don’t have much experience with these, I currently have the pump out, valvebody off….here is my plan. If some of my terminology or ideas is off or whatever, PLEASE correct me, i am here to learn.

1. Thread and plug the 3/4 accumulator feed hole and not put any pistons in it. I was just gonna smash a checkball in it, but i thought threading it and plugging could be “reversable”. This is down in the 3/4 accumulator cavity in the case. I have read this will supply the gears with better lube all the time, and make the 3/4 shift solid.

2. I am leary to use the super servo after reading about it (for this application) so I think the Corvette servo with HD2 Blue spring. I have the spacer rings to adjust the band if needed.
Should I grind the relief cuts in the spring seat thing on the second piston or leave it solid? Some say it helps drain faster, some say it does but doesn’t actually help anything.

3. I dont know what to do with the 2nd accumulator, I want a firm but not harsh shift from 2/3. If I am getting on the interstate and at 8-10 psi, I want it to shift firm/fast but not if I am just cruising around part throttle. So i am unsure about the washers and springs in the kit. I have read that combined with the corvette servo makes it harsh at slow load/speed upshifts. I have pinless accumulator pistons if that would be better.

4. I have a pump upgrade kit that is supposed to be for high rpm applications. I was gonna shut off the PWM as well. I have replaced a pump before, but any tips/trucks welcome.

The rest I was planning on following the directions for the HD2-D kit as it says. Even the VB separator plate stuff if you guys recommend.
I have read where some guys dont like to drill out to .093 on certain holes in the separator plate, they only go to .055 for the AFL holes.

I have read so much and printed a ton from users Clinebarger, MaroonMonster, Franks, PBA, VortecIroc, and others. I get there are many ways to do this, and I am just a beginner at this, so whatever way is least likely to mess it up. I dont want to be drilling holes all over the place if a spring or something else is an equal fix.
For this trans, I want to stick with the pump/VB/servo stuff, then learn on tuning and stuff.
I have also bought the ATSG manual and the revision manual for diagrams and to help learn the parts and correct names of things.

I dont want it to slam into gear like when going from p-d or into reverse or whatever. I would actually be ok with it chirping the tires on a 1-2 shift under heavy acceleration AS LONG AS its not gonna break stuff in the trans. I understand any aggressive driving/towing should be in D, and 4-2 downshifts are bad.

I also have HP, which I can change somethings there, but again, kinda new to it as well.

Thanks guys

 

You are off to a good start.
First, understand that the 2nd accumulator affects the 1=>2 shift, not the 2=>3; maybe you must wrote it wrong. Put at most one washer in the 2nd accumulator, using the HD2 springs. If you are also mixing in Sonnax parts, DO NOT use the Sonnax pinless piston with the OEM or HD springs as that will jam it up; if using the Sonnax pinless piston, use only the supplied Sonnax spring.
I recommend skipping Step 5 related to replacing the 1-2 Shift valve; the HD2 valve lets your force a 2=>1 downshift at any speed. This would let you downshift to 1st at excessive speed and blow the engine.
Lots of people drill the 2-3 Shift hole to .125", partly to counteract any small leakage in the 3rd feed circuit.
The Sonnax HD 2-3 Shift Valve is highly recommended as it then applies the Overrun clutches for all gears while in D3. (The ATSG manual is incorrect in this area.) With the HD 2-3 Valve installed, aggressive acceleration is then best done in D3. (Without this valve, there is disagreement on whether D3 or OD is better.)
Good luck with all this.

 

thanks!

 

The Sonnax pinless pistons will work, you just can't put a spring on each side of the piston. You can only use springs on one side or the other. TransGo likes to put a spring on each side of the piston. This will limit the travel of the Sonnax piston, and you won't have very much accumulation.

 

Looking over everyone's advice all looks good, I would not get to carried way with the 1-2 shift feed .093 Is what I use there with the vette servo and bit smaller with the sonnax and even smaller with the superior servo. Though with the stock band I do not suggest anything bigger servo wise than the vette servo.
The suggested .125 for 3rd is fine.I use .100 in my builds but then I a have addressed all the leaks AKA BORE PLUGS (rev and fwd) . End caps (4-3 SIGNAL and CONVERTER REGULATOR VALVE)
I would consider this mod FTOVERUN its simple and greatly improves durability of the sprag https://cimg6.ibsrv.net/gimg/ls1tech...8014b77ea1.jpg

 

I see the pic Frank....what are we looking at...how did you do it....and why ( why is my fav question )

 

As you see the circled area, You see two holes plugged and the gasket cut to connect two channels. This keeps the overun clutch on in all fwd gear positions in all gear but actual 4th/ Doing this adds support for the input sprag assembly . I do this with all my builds from stock to the stage max .
Its IMO one of the most important mods I do. The downside is you will feel to less or greater extent the 3-2 coast downshift which is normally not felt in D OR OD positions.
But basically it's great insurance for the sprag.

 

So finish threading this in here, leave everything out

Used a lil solder on these, fits good


So with this bathtub mod, i dont need the sonnax 2-3 valve? I have one if needed. What else for a good firm 2-3 shift?

 

sonnax 2-3 is a waste of money you can do same thing with separator plate mod. Frank's mod is superior to Sonnax. Maroonmonster does similar mod but has his own custom plates made AFAIK.

 

well 💩, lol i guess i bought one fir nothin, but all good!

anything else you guys recommend without pulling the gearsets on this one? Can I slip a wide band on the factory drum, or does it need to be machined first?

I have the remainder of the HD2 kit (which I think is just accumulators, boost valve, and i am putting in a “high rpm” pump kit. I think thats it.
I do not have aluminum replacement pin style pistons, i have pinless. How do I setup the spring for that? What color/which side? This would be for the 1-2 housing. I got a couple check ***** with them, but no instructions.
I would like a firm tire chirp shift under WOT (or as much as possible without damage), but i dont want it to slam just accelerating normal either.

I apologize for the repeating, I work 13-14 hr days now so its hard to keep things in order.

 

i am assuming you only cut the gasket for the bathtub circuit on the valvebody side, NOT the transmission side correct?

On my 2nd accumulator, the piston is plastic and it just had a blue spring. In the HD kit it shows the aluminum piston, a spring seat, then all their washers/spacers.

I was just going to install the one spacer, but i without the spring seat and the aluminum piston I can do anything here, as they are wanting to put an orange spring on the other side of that piston, obviously not possible with the plastic piston.

It looks like I can pull this pin, smash a checkball in, and use the pinless pistons here? If so, what springs and washers on either side?

 

If I was doing this shift kit, I would install whatever spring is stock back in it with the pinless piston. If once you get it all back together if you what a harder 1-2 shift you can install a Sonnax spring part no. 77704s or add a TransGo spacer or two. It may take some trial and error to get it to shift the way you want.

 

Ok I had a chance to get back to it…

1. Corvette servo, blue spring added
2. 3-4 case accum is plugged, cavity left empty
3. blocked 3-2 shift AND control valves inboard
4. Chamfered manual valve for reverse
5. added white spring to actuator valve
6. blue (56 oz) spring 2nd accum bushing/valve
7. Pinless piston/stock spring 1-2 accum VB
8. New style iso-conv valve blue spring
9. Franks “overrun mod” in separator plate

i drilled all the holes out per transgo instructions, but after reading more, it seems like .093 is to large on some? And now with some of these mods, they are too small.

since I blocked the 3-2 valves, it looks like i need to modify the spacer plate to the right sizes….

also wondering about removing the checkball and plug the separater plate beside the BR hole…then increase the size of the band release hole to .106 and the third apply to .140

i have found quite a few variances mainly on this site from different trans builders in many threads about hole sizes for some of these “custom” mods.. I understand you guys do these custom for each application, but is there even a general rule us beginners could go by?

thanks all for any help

 

in my experience ...the 93 hole for 1-2 shift hole is to big.....just my opinion

 

The TransGo sizes should be pretty close for most people, put it together and see how it shifts. If you're not happy with some of the shifts at least then you will know which way you need to go with separator plate hole sizing.

 

i generally leave the 1-2 hole stock or about .083 but to each his own, And of course what you did with the 1-2 accum and the VB accum plays in too.
For example in my Impala SS it has .093 for 2nd but the 1-2 acum and the vb accum are stock and I landed with a nice firm but not overly aggressive at all throttle openings with the corvette servo .

 

agreed. I wouldn't use the pinless pistons or the transgo kit myself. I used transgo stuff for a long time but the stock springs work fine.

​​​​​​agreed. i wouldn't go over .070ish" personally. i am NOT a fan of a firm 1-2 shift especially in a daily driver with stock diameter converter. a gentle bump is OK but an overly firm/hard gets annoying & potentially dangerous (if you're chirping the tires) IMO. I usually like .063" and then go from there.

 

2 checkballs in the case, everywhere I read says just one?
[img alt=".104 band
.110 on 2-3 and 3-4
.082 on 1-2
"]https://cimg4.ibsrv.net/gimg/ls1tech.com-vbulletin/2000x1504/img_0710_3ee54bb727cb05e7897b940d9c1791d960c51e63. jpeg[/img]
.104 band .110 on 2-3 and 3-4 .082 on 1-2

After the “overrun bathtub mod”, do I still leave that ball in?

Pinless forward with stock spring, small yellow Transgo spring on the other one.



Does all this look ok fellers?

 

I haven't done Frank's over run mod yet. From the pics that I have seen, it looks like you cut the gasket wrong. I would not think that the check ball in this location would be used. If I'm wrong here hopefully Frank will correct me.

There are two check ***** on the case side one at the very back of the case that is encapsulated, and one for the 4th gear accumulator. If you have blocked the 4th gear accumulator this, check ball can be omitted. The check ball at the back of the case can also be omitted.

 

It is cut right, you can keep or remove ball makes no difference