OffshoreDrilling's DIY 6L80 transmission rebuild

[OffshoreDrilling]

The transmission in my 07.5' Sierra Denali has been on the fritz for over a year now. I bought the truck used with 80k miles on it two years ago and have put almost another 40k on it in that time. There's evidence the truck had done a lot of towing in its previous life given that it had been wired for a brake controller, airlift airbag system installed on the rear axle and holes in the bed where a gooseneck or 5th wheel had been mounted at one point. I got one hell of a deal on the truck and knew Id be digging into the trans sooner than later.

My current issues are an intermittent shift flare on the 2-3 and 3-4 gears, banging into gear on downshifts (it literally sounds like someone is taking a hammer to the trans some times ), and it likes to go into limp mode during the summer or high trans temps, locking itself into either 4th gear or 2nd. A couple key cycles usually clears this. However, this is not fun to deal with while towing 6000lbs+ worth of boat and trailer or in general. I've been kicking the can down the road so to speak and decided to finally nip this in the butt.

A friend passed along a "I know a guy" reference for a rebuild. After some back and forth he sounded like he wanted to dodge the work of the rebuild because "they've been coming back with failures a lot" and recommended me to replace it with a reman'd trans with a warranty for his great cost of $3500 parts and labor. Given my research, that would leave me with a $2000 trans and $1500 in his pocket to R&R. Get lost.


This led me down the path of looking what it takes to do a rebuild on my own because I'm a cheap ass. I've never delved into a trans further than replacing valve body components. A full rebuild on a 6l80 looks completely do-able. a very large pair of snap ring pliers is the only specialty tool that is 80% necessary. I'll probably end up making my own set if I cant scrounge them up at work.


The build:
I snagged a 120k mile 6L80 locally on Ebay from a wrecked 08' Hummer H2 for $675. Saw a video of the truck running and driving, and its never been towed with. I could probably drop this into my truck as-is and be fine for another 40k miles. This will be my build core. I can't afford the down time with only one vehicle or the chance I'll fuck up the build and have no backup. If the build goes well I'll re-do the Denali trans and sell that or get at least $500 for the core.

I'm planning on the following upgrades:
-Brand new GM pump, updated design in 2010' that eliminates some known problems. $165.23
http://www.amazon.com/gp/product/B0049Z7DVQ/?tag=tcg21-20

-Rebuilding/upgrading the valve body components with the Sonnax Zip Kit. $220 on ebay
http://www.sonnax.com/parts/3505
These guys make some AWESOME stuff. I know for a fact FLT uses many of their components in their builds.

-Replacing all the clutches with OEM, steels only if they're burnt once I open it all up. $58.54
http://www.amazon.com/gp/product/B001UE1SXS/?tag=tcg21-20

-TIG welding the clutch drums at a common cracking point. $=Case of beer for a friend.

-Sonnax 4-5-6 Clutch Apply Piston Kit

-Sonnax Pressure Switch Rebuild Kit

-Sonnax HD Pump Slide Spring

$153.34 for the above three.

-Installing a brand new ZL1/CTSV converter. They have a slightly higher stall speed and a much heavier duty lockup clutch. $265


-misc. parts: fluid seals filters. Shouldn't run me over $100

Total build cost so far: $1,637.11 and a hefty Portillos bill for some shop time and lift usage.

Click to read more...

 

[Gav'sPurpleZ]

good luck dude

 

[EmersonHart13]

I was hoping you would build thread this.

 

[bikrboy128]

good luck man! GM auto transmissions aren't hard to do at all. like anything it's a matter of taking your time and remembering where everything went

 

[OffshoreDrilling]

good luck man! GM auto transmissions aren't hard to do at all. like anything it's a matter of taking your time and remembering where everything went

interested in swapping the transmissions when the time comes? Refuse to pull this thing on my garage floor. Shoot me a price or tell me to fuck off. I'm cool with either

 

[EmersonHart13]

BP speed shop ftw.

I'd show up for this.

 

[bikrboy128]

interested in swapping the transmissions when the time comes? Refuse to pull this thing on my garage floor. Shoot me a price or tell me to fuck off. I'm cool with either

bring food and drinks to the speed shop one night and we can knock it out

 

[OffshoreDrilling]

You da' best.

 

[EmersonHart13]

 

[syP]

bring food and drinks to the speed shop one night and we can knock it out

ill be there.. just tell me when

 

[bikrboy128]

now it's a gang bang. :naughtyd:

 

[EmersonHart13]

That's how we like it here.

 

[OffshoreDrilling]

bought the pump, clutches and new filter on Amazon. $265.76 I went with OEM clutches, seems to be problems with the alto ones after doing some digging. Also found out the pump comes with all the seals needed for the trans as well. I'm going to leave the stock steels in the clutch packs as long as they're not looking burnt.

total of $940.76 so far.

 

[syP]

shoulda hit me up!

 

[OffshoreDrilling]

I ended up buying a zip kit from Sonnax last night. Figured id be better off having all new parts in the trans than swapping things back and forth. Everything I have listed in my first post, minus the converter, has been purchased and is on its way to my door.

Thinking I am going to buy a couple big drip pans to do the assembly and tear down on. My garage is going to be a mess otherwise.

 

[Mr_Roboto]

You'll pay for your tools the first build if you don't make em yourself (Some you can) I did a 700R4 and it's one of those things that still impresses people when I talk about it. So many people build engines, not everyone builds boxes. Do you have the ATSG books or something else?

 

[OffshoreDrilling]

I posted earlier, the only tool that you 80% need is a 3' long pair of snap ring pliers. You can spin it around and get to the end with a screwdriver to pry it away from the case. Im going to give that a shot first before I go out and spend $140 on something i'll use once. they'd be easy enough to make as well.

No ATSG book, theres enough information floating around on the internet to get by. I'm pretty familiar with taking compacted equipment apart that i don't have manuals for anyways. I do it on a daily basis at work. Pictures and a clean, organized workspace goes a long way.

There are so few moving parts in a 6l80 that it blows my mind. The only thing really tunable with one as well is clutch clearances. Makes it pretty hard to fuck up if you're using all OEM parts.

 

[Spivitz]

Nice Man, you've got dem skills
GL getting it fixed sooner than later

 

[OffshoreDrilling]

Picked up some more Sonnax parts this morning.

- 4-5-6 Clutch apply piston kit.
The 456 clutches are -the- major failure point on these things. Basically, the OEM apply piston and clutch backing plate either warp or are only applying pressure to the outer edge of the clutch due to the shape. It causes the clutches to wear out in a bevel shape pattern. This kit has a redesigned piston assembly and backing plate that fixes that.

-valve body pressure switch rebuild kit
self explanatory
-Heavy duty pump slide spring.
Bought it because it got me free shipping. It keeps the pump in the high volume position at lower RPMs

 

[OffshoreDrilling]

This is just about every part made for this trans. There is a billet 300M output available for around $700, and I could spend a few hundred more bucks on heavier duty clutches. They all seem hit and miss for reliability. The OEM drums and backing plates can be machined down to accept an extra clutch/steel as well but its not worth it to me. With a solid tune these things seem to be holding 500WHP all day long in stock form.

A performance rebuild is going anywhere from $4000 to almost $6300

 

[OffshoreDrilling]

Finally got started on the actual work tonight, instead of finding things to spend money on. A transmission full of ATF and not attached to a vehicle is very hard to drain and not make a giant mess. Spilled probably half the damn pan's worth on the garage floor. Easy enough to clean up with some oil dry. I tried to take a lot of pics to keep this interesting while not changing gloves every two minutes to grab the camera.

The pan of course has no drain plug, leaving you to slowly try and remove the bolts in a pattern that leads the fluid to drain at one corner. This only kinda works. You're still left with the three quarts sitting in the pan after everything seeps past the gasket.

I rested the tailshaft on a jack stand and the bell housing on top of a couple 4x4's to level it out. Slid a drain pan underneath and undid the trans pan bolts as necessary. After it was drained, I supported the pan with jack, removed the bolts and lowered it the rest of the way. This is the trans after the valve body, pan and transfer case adapter had been removed.

pan, gasket, t-case adapter. HOW EXCITING.
The magnet in the pan had very minimal junk stuck to it. Not that it matters, its being rebuilt

Valve body before I cracked into it.

the heart of the beast. They look very intimidating, but are quite simple.

http://i.imgur.com/NLSeuZv.jpg
Parts that were swapped out of the valve body. The plugs were replaced with O-ringed ones, valves with new upgraded components and springs, one of the holes got a sleeved pressed into it. All the parts come in the Sonnax Zip Kit

replacing the switch components on the TECHM (electronics part of trans) they are fluid actuated switches. You can see the orange discs are torn or starting to tear.

This is what the rebuild tools and parts look like to fix that. The orange discs were a MF'r to get in correctly. From the factory they are installed, and then a piece is riveted over them. You rip the old ones out and then magically have to fit an approx 3/4" disc into a 1/2" hole and get it to lie flat.

All clean, bolted and torqued together back to spec.

Next up was to get the guts out of the trans. I started with the bell housing/pump. On the 6l50/80/90 the pump face is actually integrated into the bell housing.

Old pump removed, pulled out the rotor and vanes, cleaned it all up. Replaced the pump slide spring with a heavier duty one (blue). It keeps the pump in a higher volume mode at lower RPM

New pump installed

This is part of the reason i went with a new pump vs rebuilding the old one. In 2010 there some upgrades made to the designate. A big one is these tabs on the O rings to keep them from spinning. They were prone to leaking past in the previous pump design

This was the fun part. I decided not to spend $120 on the proper snap ring pliers to remove it. You're able to get a screwdriver behind it and work it out relatively easy. When I say relatively easy, I mean i was ducking to the side waiting for it to fly out at a high enough velocity to embed itself into concrete.

All the internals out! This is where I called it quits for the night. I built this tray out of lexan to have a clean space to work without needing to go through rags like crazy

 

[SleeperLS]

Looking good man! I hope I can gather the courage to build a trans someday. Excited to see how it turns out!!!

 

[EmersonHart13]

Loving that table. Excellent detail. This is awesome

 

[OffshoreDrilling]

Thanks guys. There is a lot of voodoo associated with transmissions I think. Mainly because people don't understand their operation like they do an engine. It's a fairly simple machine in comparison. Often there are a lot of specialty tools required to work on them and you aren't typically replacing a single part like you would an engine, it's the whole thing that is being disassembled.

 

[OffshoreDrilling]

Debating the merit of doing the converter I have mentioned in the first post. This is the only part I have yet to purchase.

On one hand it is super cheap and will give a modetate performance gain.

On the other, if and when I do put a power adder on the truck I'll want something different. I'd be okay with spending the money at that point for a more agressive aftermarket converter that will hold up to power and towing.