The Decision is Made

[General Stalin]

So, I have decided I am totally gonna transform my old '95 Tahoe into a dragster, maybe even make it track only.

First order of business is to finish building that 383 stroker I started building like over a year ago. The awesome part is now I have no time constraint or investment constraint, so I can go all out and get a full-roller valve train and a set of AFR aluminum heads for it with a sick racing cam.

Once the weather finally decides to ******' break around here (been raining here for like 3 straight weeks... and it's going to rain all this coming week as well) then I'm gonna get my truck out of the back yard and start pulling stuff apart and having a ball. The question is with my transmission... do I pull out the 4L60E and rebuild the whole thing with nice parts and servos and a shift kit? Or do I sell it or something and look for a better tranny? I know the 4L80E would be prime, but wouldn't a stout level 3 4L60E witha nice stall be able to handle gobs of torque anyway?

I also think I want to convert it to 2WD to help lighten up the load. I picked up a neat little gem at the junkyard over the spring I think I will pop in the Tahoe for the time being: I found a GMT400 bodystyle 2wd 3/4-ton work truck with a G80 locker (it's an interesting combination). Best thing is, the rear end was a 14-BOLT SEMI-FLOATER! So, because it's a 2WD light duty truck, but also has the 14-bolt rearend, it happens to have a 6-lug setup. I measured the axle from drum to drum and sure enough it will bolt right on to my truck no problem... so I pulled it, cleaned it, painted it in bed-liner, and painted the diff cover in engine enamel and she sits and waits to be installed. I tested the locker by hand and she still works fine

So what do you guys think? I would really like some opinions on the transmission, and also some input on the G80 locker because I have never used one so I don't know how well they perform or how reliable they are.

 

[foreverfalcon40]

700r

 

[DJTricky]

yeah i have the 700R in my hoe. Build by absolute transmissions and its rated at 700 horses. My rear end is now set up for 600 horses. So im good for another 200 horses

 

[General Stalin]

So you're saying get rid of the computer aspect all together. I'm thinking if I am going to be just racing it, maybe it'd be best if I just got a TH400 or something? It probably won't see highway, or at least not much (I'm not gonna say never) so 3 gears would probably be fine, and a TH400 would probably be a lot cheaper than a 700r4 as they are a dime a dozen. Hmmm....

 

[95TwinTT]

Don’t even bother with the 4L60e.

This is the voice of experience. I have been there and done that. I started with a 6 lb boost supercharger on the tahoe on the first round. Blew the trans and built it up to take the extra power. That lasted for a while.

Then I went to a 15 pound boost supercharger and soon after blew the tranny again. Built it up to take the added power and again it lasted for a short time, then toasted that one.

This also includes moving to the separate TCU controller, early on, since the ECM could not control it properly with the higher horsepower.

Meanwhile, I am doing similar things to my Camaro Z28, which still has the ultimate 4L60e tranny. It is doing ok, but mostly because it is only asked to mover 3200 pounds of car.

I was all the way up to holding 320 psi, on the 2/3 shift to make it hold, on the Tahoe. Now, with the 4L80e trans, I am running normal pressure on the 2/3 shift and it will chirp the tires.

The 60 and 80 in the transmission ID stands for Kg Force Meters. When you convert it to foot pounds, it looks like this.

4L60e 60 Kg Force Meters = 442.97 Foot Pounds

4L80e 80 Kg Force Meters = 578.64 Foot Pounds

This is the limit of the factory design specs.

You need to look at a 3 / 4 clutch pack to better understand the limited ability of the 4L60e.

The 4L80e is easy to come by, and it fits nicely in your Tahoe. It does have a taller first gear, but works well with a 4:56 rear.

In the long run, you will save lots of money, because of not having to screw around with the tranny ever again.

Regardless of the added power you end up with, the trans will always have to struggle with the added weight. That is what kills them on these trucks.

Just my humble opinion, but if you have the time, you might as well do it right.

 

[bowtiefreak]

do not use the G80. Nothing more about it other than it will fail. Get a tru trac.

 

[961500]

Avoid a 700r4 it will be a nightmare I went to one first and rebuilt it about every 14 months. Currently have a th400 setup love it works great this is what gm put in the 454ss models buddy of mine built his with a gear vendor overdrive to get it to a six speed truck was wickedly fast with this setup.

 

[General Stalin]

Yeah, I have heard the 700r4 is shit unless you build it up anyway, so I don't think I'll be going that route. TH400 or 4L80E would be decent, but, not sure if you know this or not TwinTT, but 4L80E's are not all that easy to come by. I have been to my fair share of boneyards and have found NONE (and yes, I do know what to look for and how to identify them) and to buy one new is at least $2000. You can buy a new, stoutly built TH400 for like $1000, or by one stock for like $600... or even dig one out of a junkyard for like $100.

I would love a 4L80E, but it just seems like odds are against me, and the Turbo 400 would do all I want it to anyway.

 

[95TwinTT]

The 400 is a great trans, if you don’t care about the overdrive. Mine’s a daily driver, so I need the OD with 4:56 gears.

The transmission shop I deal with, keeps used 80’s on the shelf. I traded my 4L60e for one he had. I think all the special parts in the 60 made it worth while for those guys. They rebuilt it for extreme use and ordered up the extra parts needed for the swap, like dip stick and tube, adapter for the transfer case, etc.

Stall speed on the TC is also a big deal as well and trans brakes are available for just about any trans these days……

 

[Ninety5PoloZ]

Well first off I have a few questions:

Are you planning on keeping the CPI or the TBI? If so your wasting your time with that IMO

Second if you are considering a th400 why not a th350? They don't rob as much power and can be built just about as strong.

But if your talking 383 with AFR heads you might as well make the switch to carb or a multi port fuel injection. If you plan on keeping the CPI or TBI with good flowing heads you will have a serious bottle neck at the intake. And if its going to be a drag/street truck a carb would be pretty easy and quite a bit cheaper than working with the fuel injection.

If I were to build a tahoe into a drag vehicle I would do a carbed 383 with a TH350 with a trans brake, and just gut everything out of it to get it as light as possible. And I would deffinately convert it to 2wd.

But on a side note look up redneck transmissions, my buddy got a TH350 for his 2nd gen camaro. I think hes running a 3500 nitrous converter with a brake and picked everything up for like $1300 shipped to his door. The car is currently running consistant low 10s and he hopes to be in the 9s this summer.

Good luck

 

[foreverfalcon40]

Why not a hydromatic?

 

[General Stalin]

Why not a hydromatic?

TH350's and TH400's are hydromatatics. The "TH" stand for "Turbo-hydromatic"

Are you planning on keeping the CPI or the TBI?

The 383 will be carbed.

You do pose a decent point with the TH350 vs TH400 transmission. Everything I have learned about them boils down to personal preference. The TH400 is all in all more heavy duty and can handle more horsepower, which seems like a decent avenue for me because if I am building a straight up drag truck, then who knows how far I will take it in the future. I would hate to end up with 600+ horsepower at the crank down the road and realize that the TH350 I built for this thing isn't going to cut it anymore, you know? The TH350 does have less of a load on the drivetrain, though... hmm....

 

[Ninety5PoloZ]

TH350's and TH400's are hydromatatics. The "TH" stand for "Turbo-hydromatic"



The 383 will be carbed.

You do pose a decent point with the TH350 vs TH400 transmission. Everything I have learned about them boils down to personal preference. The TH400 is all in all more heavy duty and can handle more horsepower, which seems like a decent avenue for me because if I am building a straight up drag truck, then who knows how far I will take it in the future. I would hate to end up with 600+ horsepower at the crank down the road and realize that the TH350 I built for this thing isn't going to cut it anymore, you know? The TH350 does have less of a load on the drivetrain, though... hmm....

Oh I completely agree, being that the Hoe is heavy I could understand wanting a TH400, but check out redneck trannys, they have some kickass deals on some bullet proof trannys. My buddy had a problem with the first one and they paid to ship it back and sent him another one before they even recieved the old one back. He didn't even have to drop it off, they came and picked it up and repackaged it.

My other buddy has a TH400 and he says he wishes that he would have stuck with a TH350 and hes pushing 800 ft pounds to the wheels, and the guy with the TH350 is pushing about 750 ft pounds to the rear wheels, but they are both in 3500 # cars

 

[General Stalin]

Hmmm... now you got my wheels turning. Maybe I'll tlak to a trans shop and see what they have to say. I mean, I was really thinking about building the trans up myself. It would be cheaper and a great learning experience, plus would get me a much deeper understanding of the mechanics and just what exactly is in my truck.