lsfanatic

Hey guys, I have read endless threads about what a 4L80E with light mods will hold but it was all for cars. I have always held myself back from modifying the motor on my truck because I don't want to worry about the trans. I do towing every now and then, and change the trans fluid every 50k. I don't drive the truck hard but I do lay on it every now and then. I currently have 143k miles on the original trans. My question to you guys is how much power can my trans hold with maybe a shift kit? I don't want to put a ton of money into building the trans because I am still saving for a 5th gen. I have a feeling it won't be reliable at anything over stock especially when moving around 7,000lbs all the time. What do you guys think?

Jake's Performance

iTrader: (2)

A stock 4L80E with TransGo HD-2 kit (modified) will work fine for you and give long service as long as it's in good shape.

If you get ready to do it call the shop for specifics on what the HD-2 kit needs to work correctly.

lsfanatic

Okay I see that is mostly valve upgrades. How much power would that hold?

Jake's Performance

iTrader: (2)

Properly done, on a 4L80E that is in like new shape (most aren't), it would hold over 1000 HP as long as the input shaft didn't fail. There are a lot of "ifs" here.

Stock input shafts have questionable metallurgy and heat treat. Mass production, lowest bidder.
I've had customers run 1200 RWHP through a stock input shaft without failure and I've seen them break behind stock LQ4's when used in heavy towing applications.
Later model units reportedly had better heat treating.

I rate the stock input to 750-800 flywheel HP. Most seem to do fine at that power level. If the car/truck is heavy, N2O is going to be used (more than 150 shot in any case), or the shaft will see spiked loads (offroad) I recommend an upgrade.

lsfanatic

Okay that is pretty impressive. I would be no where near 1000hp. Honestly I had a cam, with ported heads and long tubes in mind. So not over 500hp in all reality. If I got really crazy maybe a whipple blower on light boost.

Obviously my trans is no where new condition because it has 143k miles on it, but I would think it is in decent shape. So the stock clutches hold up relatively well in these? I like that the trans doesn't even have to be removed to install the trans-go kit. How hard is it to do yourself? I don't have much experience with automatics but do all the other work on my truck.

Troy5061

iTrader: (19)

My car just made 700whp on a mustang dyno through an unlocked craigslist $100 4l80 with an HD2 kit I put in. I think it had 130k miles on it. Its been in the car a year and hasn't broken yet.

Troy5061

iTrader: (19)

Just saw you have a 2500hd haha, might be different for you my car is only 3450lbs.

lsfanatic

That was honeslty my biggest concern. I have read ratings for stock transmissions that state a certain power level and a certain vehicle weight. So I am guessing the resitance to the vehicle accelerating increases the stress on the trans. However Jake's said it would be fine, so their expience with 4L80Es makes me fairly confident in their advice. I am just blown away that the stock clutches will hold that kind of power.

NorthTexasConverter

Stock Hi Energy clutches (that came in the later model 80Es like you have) are what we, Jake, and many other builds use for our performance builds. They are an excellent clutch, and they are not even a tiny worry in the back of my mind whenever they are used. I wouldn't really feel comfortable saying it can hold 1,000 hp, but like Jake said, there are a lot of "ifs" there. Right out of the box, the kit is not perfect but it's not a horrible option for guys such as yourself without much, if any, transmission experience.

lsfanatic

That is very good to know. What would you guys think is the next weakest link in the trans other than the input shaft?

Also how much firmer would the shifts become with the shift kit?

NorthTexasConverter

The forward hub would be my recommendation to address. It's also the cheapest billet part among the group.

I have no idea how to answer your other question. It's all subjective. Either ways, TransGo has several recommendations based on their separator plate design that you can drill the holes out too with around .096" being what they consider "firm".

mrvedit

Keep in mind that "stock" 4L80E are used in mobile homes which are much heavier than your truck.
I barely know "squat" about 4L80E, but from reading all the posts here for many years, IMO, the Transgo shift kit combined with Jake's (or NorthTexasConverter's) "mods" is all you need at you power level. Later a stock rebuild with a billet input shaft is good for 750HP+.
In short, I think you are worrying too much.

sardo_67

iTrader: (2)

Jake and TX converter....

I just picked up a complete drive line from a 2000 Chevy 2500 truck, 6.0/4l80e/t-case (pull lever type) and will be putting the 80/tcase behind my built up LM7 with around 500 crank hp then into my jeep cherokee on custom axles with 37-40" tires.

I don't plan to neglectfully abuse it offroad but other than a 3500 or so stall and the shift kit what's something else that's good while I'm there? I like the OP have a larger vehicle and non street/strip use.

turbols427

Just read this article, https://www.autogespot.com/the-legen...ton-martin-db7, and it says our 4L80E could handle 440lb of torque if taken from the 99' DB7. Does anyone know if that was just its rating from Aston Martin and it can handle more than that stock with lower mileage or if that really is the max torque it can handle?

mrvedit

Unless Aston Martin bought severely downgraded 4L80E, or rebuilt them themselves <grin>, they can handle much more power as described in this thread.

vorteciroc

Myself and others have Early-Model 4L80E Units with 2,500 HP going through them...
A small diameter multi-plate lock-up Torque-Converter and great Cooler-System is a must!

vorteciroc

Not at all.
They actually received the "normal" 4L80E but with "Humvee" Overrun-Bands (Low-Reverse and Intermediate).

Similar to how the THM400 went into Rolls-Royce and Jaguar years ago.

mrvedit

You are such a crazy wealth of even the most trivial information about GM transmissions. It would not have surprised me if you had listed the serial number range of the transmissions sold to Auston Martin. No, don't go look it up.
Seriously, we greatly appreciate all the information you share, and how you take the time to explain it all to us, including the incredible diagrams you create.

truckdoug

iTrader: (25)

didnt a Jag come with an 80e at some point?

truckdoug

iTrader: (25)

if so, hopefully they didnt put Lucas electronics in it haha