Beefing up a 4l80e

Redneck357

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If you have a BBC with enough hp/torque to get the torque converter to lock in 4 gear can you tow in OD? Or is that still going to burn stuff up? My trailer weighs 10,000 lbs. that’s what my k3500 is rated to tow. I’m swapping a souped up 454 into it and am hoping to stay in higher gears for the duration of my haul. What should I do to the transmission to keep it from burning up? I’m thinking a torque converter with the stall speed of 1500 and an HD2 kit.
 

yevgenievich

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it will be hard on the lock up clutch and an overdrive section. Due to thrust load, I seen recommendation to rollerlize the transmission. I am going to try a stock stall, but tripple disk billet torque converter. It will also lockup with in 3rd
 

slovcan

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So, my 1997 K2500 with the 454, 4L80E and tow package can't safely tow 10,000 lbs without risking the transmission? I wondered if towing in 3rd would be safer, but now I hear the TC locks in 3rd, as well.

I don't expect to ever tow more than maybe 8,000 lbs, but I sure would like to know the real limits.

As an aside, I have the Black Bear Performance ECU with the basic tune for regular gas. The first thing I noticed - apart from the apparent loss of 1,000 lbs of truck weight - was that the TC locks at low cruising speed (as low as 30-40 mph) and as soon as I lift the slightest off the gas it unlocks and almost feels like a momentary slip with a little bump up in the revs of maybe 50-100 RPM. Makes for very little engine braking. I did ask for the slightly quicker shifting option (shorter time between gears when upshifting).
 

yevgenievich

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Lock up in 3rd will be easier on the transmission. 4l80e strategy is to unlock tcc when near zero tps. I had no issues towing in OD with completely stock 454/4l80e, but only about 6-7k lbs. But if a lot of hills or lower speeds, I let it stay in 3rd
 

slovcan

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Lock up in 3rd will be easier on the transmission. 4l80e strategy is to unlock tcc when near zero tps. I had no issues towing in OD with completely stock 454/4l80e, but only about 6-7k lbs. But if a lot of hills or lower speeds, I let it stay in 3rd
Excellent! Thank you for that. I don't know why I didn't notice the TC unlocking like that before. Maybe with the tune I am using less gas pedal for my normal driving. Good info, thanks!

I don't see hauling more than a flat car trailer with a 3000-4000 lb car on it, maybe a covered one. It will be rare, in any case.
 

stutaeng

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I think you will be okay. These transmissions we're rated pretty high from the factory. 22k gross combined weight rating.

Edit: also wanted to mention that the overrun clutch does not seem to be a heavy wear item on these. In fact, often times when you tear them down you can even still see the friction plates manufacturing information on them.
 
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tayto

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if towing on flat or down hill I think OK to be in OD. going up hill pull the lever into 3rd. also note if you leave the shifter lever in OD/4th, even if the transmission down shifts to 3rd it is still different than manually pulling the lever to 3rd. the difference is the overrun clutch is not applied unless the lever is pulled down to 3, 2 and/or 1 ranges. this clutch backup the sprag and generally has more holding power . sonnax makes a kit that allows the overrun clutch to apply even if in the 4th gear range.
 

evilunclegrimace

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One of the best things that you can do to increase transmission longevity is to keep it cool. Install a larger transmission cooler in place of the factory one and think about plumbing a temperature gauge in the system. 170 degrees would be optimum and 200 degrees would be the highest temperature that you would want to see. Transmission fluid starts to break down at 225 degrees and every 25 degrees above 170 starts to shorten the life of the transmission.

 
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