I have a TH400 that I've beat on for a while in my LSx swap 67 Tempest, it is a unit I got for about $150 and its on its last legs. I bought a built TH400 with reverse manual valve body and trans brake from my neighbor who races an 8 second nova. This transmission is good for about 900+hp and I got it for $1k.

My plan was to put it in my Tempest, but I daily drive my beast to work and like to jump on the freeway for about 4-5 miles to shorten my drive. I'm usually churning about 3300-3500rpm on the freeway with the TH400 and the 3.73s out back. The car is bulletproof reliable other than the tranny, and I'd like to drive it on longer (1-2hr) drives and so I thought I would get a 4L80e in there and found some higher mileage units on car-part.com near my house for $800.

Only downside is I need a new torque converter, and probably a new driveshaft for the new tranny, plus my motor is putting out about 500hp and I want to put a 150 shot on it soon too. So I am going back an forth on selling my built TH400 that is sitting in my garage and getting the 4l80 and all the goodies to go with it, or just popping the TH400 in and dealing with high RPM cruising.

What should I do???!!!

 

If it were me, I would do the 4L80E without a question... I had aTH400 in my TA, and it was fine around town and even short highway trips - but, I always wanted to do Power tour and stuff like that and there was no way you could cruise at 70+mph for a long time. But, it really comes down to how you want to use the car... only you can answer that!

 

4L80e all the way for anything driven a little more than a few miles a day.

 

4l80e, so much more than just another gear

 

Another vote for the 4L80e...you'll love that extra gear. I'll bet you'll drive it more than you think once you go overdrive.

 

With my 80,3.73s and 26" tall tire I run 70mph at ~2600 rpm. Love driving it on the highway...wish it cruised at a little lower RPM but my next set of taller tires might help out a little.

I recommend everyone trade up to an overdrive trans when they talk about needing a new one/rebuild. They hold the same power as the old "brutes" but have an extra gear enabling you to enjoy it more than just at race events or around town...it really is win-win

 

So it looks like I have a built TH400 for sale. Lol. Thanks for reinforcing my gut instinct on this you guys, I'll be grabbing the tranny tomorrow at lunch!!!

 

I have several 4l80e 1ton trucks. trans are bullet proof. and if you need it stronger look up quadzilla.

 

I'm going to just grab one from the truck dismantlement place and see how it holds up, then later I may go bigger.

 

Get a stock 4l80e put a good converter and a trans go shift kit there's guys on here with over 600rwhp and they seam to last that way. 4l80es are good stuff. I have the rossler manual black box. Runs good

 

I'll have to look into that black box from rossler. Definitely need the shift kit for sure.
600 rwhp is about the max I plan on going right now so that would be perfect

 

Yup stick with 4l80e.

 

This what mine is in also...(1986 C-30 dually, LQ4/4L80e transplant) I can beat on this thing like It owes me money all day...jump in it the next day and run 600 miles with my trailer...never lets me down.

 

IF you look at the 4L80E and the turbo 400 side by side, they are almost perfectly identical. Rumor is the L80 is just a 400 with an extra gear. And what a difference that gear makes, too!!

Check out this website for the gear ratio's of the different transmissions GM has offered. http://www.chevymania.com/tech/trans-ratios.htm

Look at the turbo 400 and compare it to the 4L80E.. The ONLY difference in gearing, 4L80E has the overdrive... It drops from 1.00 to 0.75. Making your RPM's go down by 25%.

If you are normally cruising at 2800 RPM with the 400, you will be at 2100 with the 4L80E, and have the EXACT SAME durability....

Jump on the 4L80E, send the 400 my way, and call this a Christmas pay it forward!! LOL