4L80E behind SBC
 

I'm looking into putting a 4L80 behind my 420 SBC. If anyone has any experience with this trans I would like some advice.
1) What year transmissions are recommended? I know there are some differences with the early vs late models but does one work better? My SHP block does have the top bolt hole for the transmission so I could use either bolt pattern. Looks like the early style (pre 97?) would probably bolt up best but the later model electronics have more controllers.
2) What internal upgrades are necessary? Motor makes 420 WHP and I run a ~200HP nitrous kit.
3) What controller is best? I prefer running it automatic with a lock up converter. Manual control option seems lower cost. Can a full manual transmission still have a lock up converter?
4) What converter? I have been looking into a Yank. Probably only 25-3000 stall.
5) Planning on a mechanical speedo extension housing. Does this present any issues with the torque arm?
6) What is best way to handle the torque arm mount? I know there are crossmembers or I could fab up a different TQ mount.

Are there any other options for overdrive transmissions that will hold up? I don't really want to spend $5k for a trans just to get a HD auto with overdrive but this seems like the only real option. All input is appreciated.

Re: 4L80E behind SBC
 

Hit the truck message boards. That trans has been behind small blocks in 2500-up trucks since the 90s. I'm not aware of anything special that has to be done to bolt it up. Bolt patterns are all the same except for the presence/absence of that top bolt, which isn't really needed anyway.

Fitting it into the trans tunnel is kind of a pain. Significant modifications are required. Not sure the details.

I'd suspect, like most all transmission-related questions, you'd want the newest one you can get.

No upgrades are really necessary. It's a pretty strong unit to begin with. Shift kit maybe, that'd be about it. Think of it as being much like a Turbo 400 w/ overdrive, mechanically.

AFAIK you need a whole other crossmember. Might as well get a X-mem/TA set.

Re: 4L80E behind SBC
 

I have not come across a 4L80E that did not have all 7 bolt holes in the bellhousing. The strongest units are the 98+ with the rearward relocated cooler line fitting. The 4L85Es that came behind the 8.1 and some Duramax engines have 5 pinon planetaries.

Re: 4L80E behind SBC
 

don't say 5 pinon planetaries...lmao..you will have a troll popping in to bash you.... :)

and here.. we...Go.

Re: 4L80E behind SBC
 

I'm still running a very well rebuilt 700r4 behind my big cube sbc. I have thought about going with a 4l80e but just haven't got there yet.

Re: 4L80E behind SBC
 

Several of my friends with older big block muscle cars are running built 700R-4s and they seem to do fine. My uncles 454 Chevelle probably in neighborhood of 400-450 HP 500+ft lb tq and holding up fine to his abusive behavior lol.

Re: 4L80E behind SBC
 

This guy Lou lives right down the block from me, and he swapped in an upgraded 4L60E into his ZR1, and had nothing but great things to say about it. He was very happy with it. Easily took the abuse from what I seen of it, and that car pulls like a mother. He street races locally, so there is no time shown of course. I wouldn't waste my time with the 4L80.

- Rob

Re: 4L80E behind SBC
 

Re: 4L80E behind SBC
 

Well that's kinda what I'm considering. A "built to the hilt" 700 is going to cost as much as a 80. Even a mild 4L80 is going to be a good bet and if it needs upgrading later at least it's installed and the controller is in place.
I have been looking into going auto for a while and my TKO 600 is starting to need work. Bearings most likely going out. It isn't broke but there a lot of metal in the fluid and making noise. Liberty can go through it with some upgrades and by the time I get that done and a clutch freshen up it'll probably cost a couple grand. May as well put that into an auto. I have a good TH 350 and 400's are pretty easy to come by and cheap. Problem is I just don't think I will like not having overdrive in a daily driven car. So, my choices are rebuild the TKO, drop in a 350/400 or just put a 700 back in. As far as overdrive autos go the 4L80 may be worth the effort from a cost standpoint.

1. Entry level 4L80 ~1800
Controller ~750
Decent torque converter ~1000
Mechanical speedo housing ~500
Misc build X member/TQ arm mount etc ~300
Around $4500 for the 80
2. Built 700 ~$4000 Less hassle but maxed out.
Both will need flex plate/bolts/shifter add ~500
3. Build the TKO/clutch ~$2000

Boy the overdrive adds a lot of cost since I could build the 350 I have or go to a 400 and be all in for $2-3000 max.

BTW do you think any tunnel mods would be needed for the 4L80?

Re: 4L80E behind SBC
 

It's more than just that though. The tunnel will need to be hammered for the 4L80, no question about that. The driveshaft will need to be shortened, and the gearing that it comes with will keep you at a lower RPM around town, and a higher RPM on the highway. This greatly conflicts with your engine setup. The 4L80 is a strong transmission if someone is looking to pull their factory transmission out and wants something stronger, but any transmission can be made to handle your horsepower. Why give yourself the added headache with a 4L80.

Either way you go, it's going to cost.

- Rob

Re: 4L80E behind SBC
 

Good points. There are +/- on the gearing and all autos have bigger steps between gears than my current TKO. I figured the converter would probably help some.
I was aware of the drive shaft length issue but hadn't mentioned it. 350/400 will need lengthened so there's a cost that way too.
The real issue is strength. My engine torque is well within the 700's range. It's only when the nitrous comes into play that torque really shoots up, especially at lower rpm and on gear changes. That's the main reason the "experts" are steering me toward the 4L80. If you take my motor torque at say 4000 and factor in the nitrous @ 200HP the torque gets up into the 700lb/ft range so the shift is really where it's got to be strong. That is only an occasional issue but it's a consideration.
Trying to keep a car daily driver friendly and make up the difference with nitrous is a tricky balance.

Re: 4L80E behind SBC
 

Re: 4L80E behind SBC
 

Re: 4L80E behind SBC
 

Re: 4L80E behind SBC
 

Check out Cahall transmissions. Builds 4l60e for some of the fastest cars in the country. His prices are good, better than rpm by a long shot. He has them living behind 9 second lt impalas. That says alot because the weight and hard launch of those cars #1 killer of a trans. Heres the website.

https://cahallperformancetrans.com/4...ds-%26-pricing

Just check out the page. Call him . He will personally go over everything and all your questions. Tell him Darren sent you. I went with a pro race with billet shafts.


4l80E is going to be extra weight and alot of hammering to get it in. You can make these 4l60E live if built right.