I have been toying with the idea of a 6speed conversion lately but after working out some numbers I don't think it is going to be worth the money.

I know that the auto B2k cars were equipped with the TH400 with a gear vendor overdrive unit. However, I don't know if it is worth the money to go that route either. First of all, the 400 is an acient transmission and second, the gear vendor overdrive unit is very expensive. Third, the TH400 robs power like no tomorrow.

So I have been toying with the idea of a 4L80E swap. I have a 91 so I know that if I drop in the 4l80e I would have to forgo the electronically controlled part of the trans. Is that possible?

Also, what kind of modification is required to go with the 4l80e, such as flywheel, trans tunnel, and driveshaft?

Lastly, will the 4l80 rob power like the 400?

If anyone's done this before or knows of someone that has please chime in and let me know.

Thanks,

Paul

 

:lurk: Interesting............

 

It robs power nearly as bad as the old 400, same design, in general.

An adapter has to be built to bolt the torque arm to the transmission tailshaft.
The torque arm has to be shortened along with the driveshaft.
Your exhaust would probably have to be modified also.
I dont think the dipstick tube for the 4L80E will work either, you might need a flexible one from Lokar.

I dont recall the exact weight difference between the two

Youll have to buy a shift controller or a separate ECU for the 4L80E. Can get very very expensive.



[Modified by vader86, 9:22 PM 2/4/2004]

 

THere is no way to just bypass the electronic control?

 

If its electronically controlled, you have to tell it to shift somehow if you want to use a 4L80E

Otherwise I dont know how to get around it.

 

From another site
[ The 4L80E or 4L80 uses the larger 32-spline output shaft and offers the highest torque capacity (over 700 ft-lbs in the aftermarket JET model). The down side is its size, at 225 pounds with converter and 31-inch overall length. With its equally huge 29.625-inch mounting location, the 4L80 is a behemoth best left to the big-block crowd. To swap in the 4L80E, the driveshaft will have to be shortened and a 32-spline slip-yolk must be used.]

Do you need to carry all this extra weight? What do you need the extra strenght for?The "4L80E" has an electronic control,someone must be able to make it work with the 4L60E system in Vettes.With the right parts a 4L60E can be made to live.
See http://www.torquedriveinc.com/

 

There are aftermarket Tranny controllers such as the TCI unit or you can use a GM truck ECM from a 93 to 95 PU or 3/4T SUVs. Getting a truck ECM is the cheapest route. I think the JEB has a billet tail housing for mounting a TH400 into a C4 or maybe it was for a 4L80E I can't remember but there was something about a rear housing that is being made by either JEB or someone in the forum for doing a C4 install. A 4L80E can also be made to run manually with a transgo shift kit, and the convertor can be locked up using a 4th gear switch and a throttle actuated switch like in the early 6.5L diesel trucks.

 

I had a 4L80E in mine when I had the 502 in it, I saw it as the only way to go.

It worked really slick. We made a tail shaft housing by milling away the side of the factory tailshaft housing and welding in a block of billet aluminum. We then drilled holes in the block in the same location as the factory driveline support beam (thats the short version, it's a little more complicated than that). I used the yoke form a 2WD pickup truck and had a drive shaft made. I used a Speed Pro controller to tell it what to do and when to do it.

I used a filler tube form a 2WD truck, it was a bit tricky, the tube normally bolted to the exhaust manifold on a truck and I had headers, so mine was not bolted down.

We had to cut the ears off the bell housing to get it to fit the tunnel. It needed a new front y-pipe for the exhaust. It also required a digital ratio controller for the speedometer to work properly.

I think that is about it, it really worked great, I had complete electronic control of the transmission and no worries about breaking it.


[Modified by Fatt Vette, 8:26 AM 2/5/2004]


[Modified by Fatt Vette, 8:27 AM 2/5/2004]

 

Fatt Vette? how much did it cost???

 

mn_vette,

Any part in partictular? The whole conversion probably cost me around $1500 to $1750, but I get alot of my parts and work cheap or free (if I do it myself).

 

does anyone know where I could get more information on the electronic controller?

 

speed pro makes one(aka F.A.S.T.) and there are a few others. But doing the manual shift isn't that bad. It's kind of like a manual tranny but without the clutch.

Hey, does JEB have a website that I might be able to find out about this mount?
http://www.tciauto.com/electronics/





[Modified by mn_vette, 5:55 PM 2/6/2004]

 

A while back, I saw someone offering to duplicate and sell a tailshaft housing, he had made up and used on his own conversion, for $900.00. That would adapt the "C" beam to the 4L80E trans.

"Jet" makes a stand alone electronics controller. Simply manually shifting is likely not going to be satisfactiry. For one thing, the trans won't have the input to adjust line pressure. Either you will get bone jarring WOT shifts at light part throttle take off, or soft slow shifts at WOT.

If you don't have the resources to scrounge, as the above poster, you are probably going to have $3000.00-$4000.00 in this conversion. Costwise, it can be pretty much a toss up with a TH400/Gear Vendor set up. Good luck, and...

RACE ON!!!

 

Hay CFI-EFI, I don't know about not being acceptable using a full manual valve body in the 4l80e. It seems like it might be a good way to go. Of coarse you will need to put in a ratchet shifter or you would go crazy trying to ease the shifter into the next gear. I have a fully manual th400 with the Gear Vendors overdrive in my car. I did this install a couple of years ago. It is an excellent setup. I can now flog the tranny relentlessly without worry. It shifts very hard and takes off like a rocket. I get all kinds of rubber going into 2nd at 55 mph with my 315's on the back. I just don't buy the statement that a th400 robs you of power. I drove my 700r4 for awhile before it failed and made no engine mods when I switched to the th400/Gear Vendors and I know from the guage in the back of my pants that the th400 did not slow me down one bit.

I would guess you could do either the manual control 4l80e or the th400/gv conversion for about the same price. I would argue toward the th400/gv. Here's why. If you manage to break a well built th400 (doubt you can if it's built right) a top notch rebuild would be something like $500-1000. How much will it cost you to have a 4l80 rebuilt? The Gear Vendors unit is warrantied for 2 yrs. unlimited mileage. If you manage to break it (doubt it) after the 2 yrs. they will sell you a whole new one for $500. This setup gives you 6 forward gears to select from as opposed to the 4 in the 4l80. The th400/gv is lighter than a 4l80. It is easier to install because the Gear Vendors unit comes with the fittings on the tail to bolt to a re-drilled torque arm. I had some trouble getting my torque arm to fit so I just made a new 2-piece torque arm and it works excellent, look at the page on my web site for pics of it.

Okay, now for all the people that claim a 700r4 can be built strong enough, that's fine. I'm happy for you to have that. I went through 2 700r4's and decided to cut my losses with that and have never looked back. Thank you.

 

So in either case, 4l80 or the th400 w/ gear vendors, you have to get a custom c-beam and drive shaft. Sounds like alot of custom work either way. Not to mention the $3+ k for the th400 setup, but you might be able to get the 4l80 cheaper, but then add in the cost of the controller.

 

I got my th400 with torque converter, all built with supposedly the best racing heavy duty parts, shipped for $1400.00 from here: http://www.dynamicconverters.com/

There is a place up here in Brooklyn Park that will shorten your existing driveshaft for you. They did mine and balanced it and installed the correct new u-joints for I think $100.00. You could redrill your existing torque arm, or come up to my house and see what I did and do the same thing for yourself by building your own torque arm. If I can do this, anybody can, trust me on this.

 

WHOA ! Hold the phone. I didn't say all you are attributing to me.
I never made that statement. It IS true that the TH400 consumes more power than the 700R4, but *I* didn't bring it up. Either your engine makes enough power that it isn't noticeable, or your "buttometer" needs recalibrating.

The 4L80E is basically an overdrive TH400 transmission, BUT there are differences. The 4L80E is an electronic transmission. It doesn't even have a governer. It won't be converted to a manual valve body, the same way as your TH400.

Just for general information, ANY auto trans swapped into a C4, will require the adaptation of the "C" beam. 4L80E transmissions are expensive. The Gear Vendor overdrive costs over $2000.00. The 4L80E transmission is equiped for a lockup torque converter, the TH400 is not. No judgements, here. No opinions, just some facts to consider. Whew!

RACE ON!!!

 

Are you saying that all 400 trans are non lockup?

 

Bobzz4,

thanks for your input on the 400 conversion. I knew there was someone on this forum that had this done. Did you do the conversion yourself? if so how involved was the conversion?

 

No lock up on the th400??? well, nuf said for me, even with the gear vendors unit, the loss from a non-locked up convertor cruising below it's stall rpm isn't good.