Storx

CORRECTION!!!, which one is best for FI 2005 A4 vs 2006+ A6 for street reliability.. is what i meant.. just leaving out the model numbers for now.. as i am still learning.,

I am planning out this future build for a fun STREET RELIABLE BUILD and im aiming toward a AUTO on my future C6 to save my knees the hassle.. Which one is more beneficial for Boosted cars?? or easier to maintain for reliability with lets say 500-600hp after FI?

I know the 4L60e is older technology and should be much much simpler to rebuild and work on... but i have read good things about the 4L80e being stout and easily reliable up to 600hp with no issues..

I know I know everyone said get a LS3 car, but if i can get a Higher mile CHEAPER with good clean body LS1/LS2 and have the difference in price savings to toss in a set of forged rods and pistons and supporting bearings and such in preperations for an FI setup.. wouldnt it be much more reliable and possibly produce better end result reliable power for street driving??

I have read that the 2005's have weaker rear axles... but if i am not looking to drag race this car but maybe a handful of times a year does it really matter??

Unreal

80 is much stronger, but a lot more work to install.

2005 rear ends are junk, axles are not an issue, it is the whole rear end that needs replaced.

For 600rwhp, I would just do a RPM built 60 and call it a day. It will handle that all day long. Get a solid rear end and some c5 axles, and you are set.

old motorhead

An '80, while being much stronger, will hide more hp. No free lunch there. A stock '80 with a shift kit will hold more power than a bad *** built '60 though.

Crawler

By reading your post I see that you are saying 4L60 and 4L80. But reading into I think you are asking about the difference between the transmission in the early C6 vs the late C6.

Those two transmissions are 4L40 and 6L80. Two different animals.

OP are you asking which stock tranny is better for boost or are you actually asking about swapping to a 4L80 which is a truck transmission and extremely heavy duty?

4L80 swaps can and have been done, but be ready to spend 15-18K to do it.

Streetk14

I'd have to agree with your logic. Sounds like he's asking about which factory C6 auto trans will hold up the best -- though neither the 4L60 or 4L80 were ever offered in the C6. I think the 2005 models had a 4L65, though.

Either way, I'd avoid a 2005 car like the plague. While I won't go into details on it, there are a lot of reasons to find an LS3 car. At this point, I don't think it will cost much more than a comparable 2006-2007 LS2 car.

And 500-600 rwhp isn't a problem for a stock bottom end LS3. Sometimes when you have someone open up your engine for "upgrades", what you're really opening is a can of worms. If my bottom end decides to explode one day, then I'll consider a forged bottom end build. Until then, I'm not too worried.

dennis50nj

Why stay away from the 05? The trans is stronger and readily available to be built or have an rpm trans built, the rear case is the weak point, easily upgraded to a 2nd generation or c6Z06, so far the LS2 is putting down better 1/4 times according to the C6 Performance List

dennis50nj

I have close to 500 rwhp NA stock bottom end and CI, 05 LS2 A4 and who knows depending how much i set the nitrous to with no problems stock trans with 3800 yank converter 373 gears upgraded rear case

Storx

Thanks yall for the input, i really meant the stock A4 vs A6 in the C6 vettes.. im not looking to throw 6k away from an built tranny from RPM.. that is way to much for what i am looking to do.. from readings both trannys can handle the power of lets say an A&A or ECS supercharger well.. just they wear out quicker.. i guess im kinda answering myself in a way it seems.. either way i would be tempted to rebuild the tranny myself.. as i have rebuilt probably 10+ trannys in my life and they were pretty simple and straight forward as long as i kept things clean.. when i had like a part that required a special tool to do or press out.. i would just take it down to local tranny shop and toss them 10-20 bucks to do the 5min action for me.. and save thousands of dollars..

Unreal

No the rear end isn't easy to upgrade to a c6z rear end. You would have to swap the output shafts in the tranny.

ATLS2

I'd go 6l80 if you like to repair transmissions

Storx

I didn't say i liked to repair them.. just figuring out which one is more RELIABLE with my power goals in mind.. i know both are pretty durable in stock form.. but i don't know the limits of them once the engine is modded.. i am am really truly trying to understand the Auto's in the C6 before i go and pick one for a Daily Driver.. i am half tempted to just suck it up and go M6 like my current daily driver.. ive been sucking it up this far and my knees only bother me occasionally.. im thinking MAYBE the corvettes gearing would allow for more comfort on the knees since its seems like i could easily cut half the shifting out... currently i daily drive a diesel car with the need to shift very often to keep the powerband within a comfortable range to accelerate and keep up with traffic..due to the narrow 1k rpm range of power with the turbo..

ATLS2

I'm not sure about the 4l65, but the 6l80 is known to be reliable at 600 with a good tune, stock. 650 whp would be max on stock internals.

Unreal

For 600rwhp I would just do a ls3 6l80. For 600rwhp in a ls2/05 you are looking at a built tranny/rear to hold up to any abuse, plus you have other quirky 05 issues. I would avoid them.

Rkreigh

I have a spare 680LE tranny for sale. trans has only 300 miles and would allow you to build it out and swap it.

also have a 4L60E that I bought for a stocker. it's a bit cheaper to build out for high hp than the 680 which is a complicated little rascal

I'm hoping the new 8 spd will offer a retrofit as I believe it's better than the rest of these fancy trannys

let me know if you need anything

dennis50nj

Are you serious, or just Unreal,- istic I have done nothing but race my 05 A4 LS2, not just the track, also street every time I drive it, wide open to triple digits and no quirky 05 problems, as a matter of fact no headlight problems or Has it been in for any recalls, no brake line not even the clip for telescoping wheel, changing a trains shaft isn't that big of a deal when switching to a Z06 rear, I have ran hundreds of 1.4- 1.3 60 ft times and 10 second passes with the stock trans and 2nd generation case

ATLS2

The top three fastest stock ls2 (05-07) are 4l65. Fastest stock ls3 (08-13) are 6l80. GoGTO did high 8s in a built 6l80, but that was in a forged bottom end. Lots of people have done 8s in a built 4l65.

Streetk14

There are too many reasons to list as to why I'd recommend going with a newer C6 model. The ls3 will make more power with less modifications, but that's not why I said what I did. The newer ones are just nicer cars all around. My cars are fun street cars, not drag cars. I wouldn't be building a C6 if I wanted a fast strip car.

Most of us don't give a damn about any "fast lists", either. I respect the dedication it takes to run good times, but it's not for me.

Storx

If i am understanding my readings correctly.. the 4L65 is easily tuned via HP Tuners without much stress, but the newer A6 tranny has to be perfect or one slipped clutch shift can wipe out the tranny??? am i reading this correctly?

dennis50nj

You are a 100% correct it does make more power, but doesn't show it on the track, the fast list is just a tool to let people compare mods and times in a real sampling situation. and even though the LS3 makes more power and has more gears, in a modded situation it runs slower ets, and the 6l80 isn't strong enough yet, and I feel it will fall to never reaching its full potential as not enough model years to be racing reliable, don't get me wrong in stock form it is very good for fuel savings and even the 1/4 with its 1st 2nd and 3rd gear ratios with its final drive gearing with 256 gears is almost the same as a 4l65 1st 2nd and 3rd with 373 gears no wonder it can beat the LS2 and the 05 4l65 bone stock with 36 more ponies, until the the LS2 4l65 gets gears & mods, that's not speculation but pure facts. the fastest LS3 automatic has the A4 10.521 @ 127.96 - Bspc608 - 08 A4 Z51 NPP - CAI, H&C, conv, 3.42, hdr, udp, tune, DR - (6805)

Streetk14

I'm not going to argue about any of the drag racing stats. The guys who post times on those fast lists spend a lot of time getting where they are in most cases. And for the 2005 models, those guys (like you, I'm guessing) have been working on those times for close to 10 years now. I'd expect the earlier cars to have better fast times just because of that.

But really, this is about building a street car. Like the OP said: a fun STREET RELIABLE BUILD . He's not looking to build a strip car. I'd rather have the extra displacement and gears in that situation. Not to mention the improved interior parts, steering changes, etc. Like I said before, the newer C6s are just nicer cars to drive and are less likely to be problematic.