building a 4l80e for 450hp and towing

[L31MaxExpress]

I will also add that the Vortec 8.1/4L85E tunes lock the converter at wide open throttle around 45-50 mph and stay locked through the upshifts as well. They make 455 ft/lbs of TQ as shipped from GM.

 

[Supercharged111]

Pretty sure a WOT TCC locked upshift would knock a drink out of my cupholder.

 

[99burbK2500]

yeah wot shifts in our dmax with the converter locked are a little harsh lol

 

[L31MaxExpress]

Pretty sure a WOT TCC locked upshift would knock a drink out of my cupholder.

I have datalogged wheelspin going into 3rd at nearly 90 mph when I still had 3.42s.

 

[RDF1]

Thanks for the info guys. I was just worried about it due to having about 270k miles on it. it does have a small flare 200rpm going into 4th at only a certain throttle input. I did flush it and run a conditioner through it about 2000 miles ago and then dropped 6 more quarts out and changed the filter. the fluid was coal black before I did the service. fluid still looks clean now. been meaning to figure out the flare into 4th but I locked the 350 up and then blew the 4.8 up I swapped in. currently putting a 10.9:1 comp 5.3 together that I plan on adding a intercooled torqstorm to. I'm glad to hear they hold big power with a HD2. ill get one of those ordered as soon as I get the truck running again. ill also look into the torque converter mentioned above.

RDF1 why did you hate the converter being locked during acceleration? wouldn't locking the converter load the engine and make the turbo spool faster? I know our 03 duramax loves when the converter locks, pulls like a damn space shuttle. of course mine will be a blower application so ill probably want the converter unlocked. also how do I identify a bu52 converter? my truck is a 99 k2500 suburban, already has the 4l80e in it.

https://www.wittrans.com/search?part=Bu52

That's the TC I've always used for most the 4L80E swaps we did. I'm not sure how to ID one. The ones from WIT link above are are stamped BU52 on the front cover.

They are cheap , about $90( I use my buddy's shop account and pay with card)

It's not that I didn't like it locked getting up to speed, I hated when it locked while getting up to speed. So I ended up setting the TCC apply only under 25 or 30% tps so if I was in boost getting up to speed it would be alot smoother and not lug the engine down. But when I got up to speed and wanted it to lock I could simply ease off the throttle and let it lock. When it locked it made enough power to never have to unlock the TC to hold speed.

Yea it would make the turbo spool faster with the extra load. But it would already be spooled up cause it was higher in the rpms. I ran a Trucool 40K cooler so never had a heat issue. It would rarely ever get over 150*. Once TC locked it would slowly drop.

I don't understand how pushing on a stock converter could be hard on a transmission but locking the TC under WOT isn't hard on one?
I put over 200k miles on that trans/TC without issue and towed over triple what the truck was rated for.


Also a Duramax makes its torque down Low in the rpms so keeping the rpms low makes a difference.

The Whipple makes good power down low also.
Turbo makes ok power down low but shines up in the mid to high rpms.

I don't Rem the tire size but the 4L80E locked in 4th and 3.42s with about a 30" tire it was 2000 rpms at 70mph and towed very good. It would make 6-7psi (6# spring in wastegate) at 2000 rpms and chug along towing 8000#.

Sent from my HiDiNg PlAcE

 

[Supercharged111]

I find 4th to be fairly useless to bring a trailer up to speed to begin with. My 4th gear for the most part stays locked once it's locked or downshifts right to 3rd. The window for it to unlock and stay in 4th is pretty narrow but it will stay unlocked while going up through the gears.

 

[RDF1]

I will admit I've never tried to tune the trans to go 3rd, 3rd locked, get up to speed then go to 4th locked.
If I still towed alot I'd sure like to try that.
I did put a yank stall in it one time. Guy said it was a 3000 stall for nitrous. It brake stalled to 5200 with 8psi boost. And towed horrible. After that I just ran the stock converter and dealt with the extra 40# rotating mass it had.

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[Supercharged111]

That thing must have left like a motherfvcker.

 

[RDF1]

That thing must have left like a motherfvcker.

You mean spin? Haha. I didn't leave it n long enough to try slicks. It didn't even have a shift extension. Shifted at 6500 and it would blip down for a split second during the shift. Thought I had torn everything up.
It sounded some kinda nasty brake stalling tho......

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[Supercharged111]

No 4wd?