4L80E Clearance Issues?

[The Lost Texan]

1985 C10 2WD Short Bed
Looking at transmission options for this particular truck. I'm leaning toward a LS3 6.2 for the powerplant. This truck will not be drag racing or auto crossing, etc. This truck has a small hump. Will a 4L80E tranny work, without modifying the tunnel? I do not want to modify the floor. Will a 4L65E work, without modifications? I apologize if this topic has been previously "beat to death". Thank you for any and all help.

 

[NickTransmissions]

Both should fit without physical mods if a 700R4 or TH400 is now installed; I'd do a 4L80E as you end up ahead in terms of durability and strength. Especially if you want to upgrade the engine in the future, the 4L80E will be able to handle anything up to 600 hp as-is while the 65E will need upgrading...

 

[Bextreme04]

1985 C10 2WD Short Bed
Looking at transmission options for this particular truck. I'm leaning toward a LS3 6.2 for the powerplant. This truck will not be drag racing or auto crossing, etc. This truck has a small hump. Will a 4L80E tranny work, without modifying the tunnel? I do not want to modify the floor. Will a 4L65E work, without modifications? I apologize if this topic has been previously "beat to death". Thank you for any and all help.

It should be no problem. The issue you will have is controlling the LS3 with anything that will also run the 4L80 unless you are running an aftermarket controller. The easiest thing would be to just get a complete takeout engine/trans/harness/pcm from something and drop it all in together. You can get a 454/4L80 from 97-2000 or an 8.1/4L80 from 01-04 pretty cheap and easy. As far as I know, you couldn't get an L92/L9H/L94 with a 4L80 in any application. They only came in the Denali and Escalades from 2007-2014 and had 6L80's behind them. I have an L9H/6L80 combo in my 2011 Suburban and it is a pretty spicy setup, but only when you get up over 3k RPM. My Burb is 7300lbs and it gets up and goes, so it would probably be a real blast in your short wide that is at leas ta ton lighter. That is still using my G80 equipped 10 bolt also... with 240k miles on it.

I got the L9H with a blown up 6L80 that had 140k miles on it along with the harness and PCM out of a 2009 Denali locally for $1500. I took it apart and cleaned everything, replaced gaskets, new cam, checked cylinder wear, then sent it with all the stock hard parts and new bearings/rings. I tuned it myself with HP Tuners MPVI3 and it has been towing my trailer around the PNW all summer like that.

https://help.summitracing.com/knowledgebase/article/SR-04851/en-us

 

[The Lost Texan]

Bextreme04
I think you might be correct on the 4L80E connecting up with the L92. I know GM currently offers a performance package that combines the L92 with 3 options: 4L65, 4L70 or 6L80. Would a 4L70E be a legit option over the 4L65E or 4L80E? Or should I consider a 6L80E for the 6.2 engine? I have a great opportunity to acquire a 6.2 engine, so I am pretty set on that going into the truck. Now, it's deciding on the best tranny option for ease of installation, connectivity and performance.

 

[Ricko1966]

With 4l80 you could use transgo 48 mod and a cheap ebay shift controller. The cheap shift controllers don't regulate line pressure,that is their big problem. The 48 mod controls line pressure.

 

[NickTransmissions]

Bextreme04
I think you might be correct on the 4L80E connecting up with the L92. I know GM currently offers a performance package that combines the L92 with 3 options: 4L65, 4L70 or 6L80. Would a 4L70E be a legit option over the 4L65E or 4L80E? Or should I consider a 6L80E for the 6.2 engine? I have a great opportunity to acquire a 6.2 engine, so I am pretty set on that going into the truck. Now, it's deciding on the best tranny option for ease of installation, connectivity and performance.

I'm not Bextreme but if you can tell me how you plan on using the vehicle, engine power, frequency of high rpm use, frequency of heavy towing/hauling (if any), i can tell you what transmission, of the ones listed above, will meet your needs, given you're weighing ease of installation, fitment/integration as much as overall durability and strength handling...

 

[Bextreme04]

Bextreme04
I think you might be correct on the 4L80E connecting up with the L92. I know GM currently offers a performance package that combines the L92 with 3 options: 4L65, 4L70 or 6L80. Would a 4L70E be a legit option over the 4L65E or 4L80E? Or should I consider a 6L80E for the 6.2 engine? I have a great opportunity to acquire a 6.2 engine, so I am pretty set on that going into the truck. Now, it's deciding on the best tranny option for ease of installation, connectivity and performance.

Nick is gonna be the trans guy to answer the holding up side of this better than me. But in my opinion, if you are just street driving a stock L92 in a short/wide, you should be totally fine with a 4L70.

I regularly tow a 6400lb trailer with my 6800lb Suburban and I had the 6L80 go out on my at 160,000 miles due to the known AFM converter slip issue causing the converter to get worn out and send metal through the whole thing. I rebuilt the 6L80 and put in a Sonnex zip kit, a billet converter, and turned off AFM. I swapped in an L9H with a TSP VVT cam this year with 240k miles on the odometer and the trans is still doing just fine. The heavy duty trucks in these years had iron block 6.0's with the same head/intake as the L92 combined with a 6L90 and those are pretty bulletproof as well.

The 6L80/90 series has a taller first gear(4.03) than either 4L series(4L60 = 3.059) and also a double overdrive... so it's a pretty good option if you are going to be driving it. I have 33" tires and first gear shifts at ~25MPH at full throttle and cruises at ~2000rpm at 75MPH with a 4.10 rear gear.

There are a lot of variables from a controllability perspective. What are you planning on using to control the engine? Is it coming with a harness and PCM? If not, you have some options to either use cheap and available OEM solutions or spend big bucks on something like a Holley Terminator or dominator system or even the new HP Tuners Core system. Those are going to be in the $1500-2k range, but they let you run any Gen III or Gen IV engine in combination with almost any GM trans. The Core won't control a 6L80 yet, but it is the first planned addition.

 

[The Lost Texan]

Bextreme and Nick,

I plan on driving it normal. Meaning I will be cruising it from town to town on county roads. In addition, I will be driving it at highway speeds (60-70mph) for the occasional weekend trip to cars shows, vacation, etc. I will NOT be drag racing, auto crossing, towing, etc. I want to build a reliable driver, with some decent power. I am a hotrod guy with multiple cars ranging from small block chevies to ford flatheads, all with 4 or 5 speed manuals. I don't know much about automatic trannys, like I do the muncie, saginaw and T5 transmissions. This will be my first LS/auto build. Finances are not a constraint, within reason. Just looking for advice, opinions on a combo set-up that will meet my needs, from knowledgeable people. The truck is completely blown apart with the frame powder coated on the hoist. I did install QA1's front crossmember/coilover system, along with the rack pinion steering- the idea was to make it more drivable. From here, I would like to make a decision on the tranny. I am almost 100% decided on the 6.2 motor, due to a friend having access to one. I also have another friend with a Stange ford 9" that will probably going into the truck. I am also asking for advice on gearing size, based on my application. I fully understand there are many variables to this, but just looking for opinions. As far as controllers, will the factory GM connect and cruise surffice? Or are there alternatives that you highly recommend? Are there controllers to avoid? Gentleman, I appreciate y'all taking the time to steer me in the right direction. Much Thanks.

 

[TotalyHucked]

So I'll just throw in my 2 cents for what it's worth. When I first built my truck I used a warmed over 5.3 (~425hp) and a 4L65E out of the donor Envoy Denali. The trans had ~104k miles on it, all I did was a fresh filter/fluid and a Circle D 3200 stall to go with my cam (BTR Stage 4 V2 truck cam at the time). I beat on the truck pretty hard, roadtripped it all over the country and got it hot several times (230+, never could get my cooler setup right) and it never missed a beat for 28k miles. I only pulled it out to put a T56 6-speed in. Personally, I'd go with a 4L65/4L70 over a 4L80 any day of the week cuz the 80E has garbage ratios and sucks up so much power. Put together a good cooling package and a well built 65/70E will last plenty fine for what you're after.

My truck is lowered 5/8 on 20s and the rear tire is a 315/35/20. I put 3.90s in when I built the 10-bolt and that was PERFECT with a 65E and my engine. Don't fear the gear, LS's like to rev. I ran ~2500 at 80 and I'd still pull down 18-22mpg on roadtrips. I'd strongly recommend 3.90-4.10 for what you're doing if you stick with a 65/70. If you do end up with an 80E, definitely go 4.10 so the power loss won't be too bad.

For wiring/controlling, I'd recommend a BP Automotive swap harness. They can get you the harness you'll need to control whatever combo you end up with and it'll keep the wiring simple. They also have the best integrated AC wiring/control options of anyone. I have a PSI Conversion harness in my truck and will never go back to them again, BP will be what I buy going forward.

Swap Harnesses

BP Automotive offers a complete selection of standalone harnesses & swap harnesses. Find the right part for your performance vehicle at the right price.

bp-automotive.com

 

[Bextreme04]

If you do any modification to a stock 6.2, you will smoke a stock 4L60 in short order. It's the difference between a 327 and a 383 in torque production and probably even more than that... its not a small difference.

Is the 6.2 you are getting from a connect and cruise setup? What trans did it already have? If it already had an 80, then it would be fine. If not... you are going to have a really hard time getting that working right. It might be easier to get a factory computer from a junkyard out of a 2008-2013 2500 that originally had a Gen IV 6.0/4L80. It should plug right into the 6.2 and be close on the tune from the get go. You could run a stock 4L80 on a slightly tuned up 6.2 for a long time before you have issues.