Need help with 4l80E swap!!!

[blueburb]

onelucky, I am thinking you may be right. I can get 13mpg with it as is with the TH400, and I really don't see getting much better than 15 with this pig even with od. I am into the 91 sub $250 and I am sure I can make money on all the parts. My TH400 works absolutely perfect as well, I kinda hate to ax it for an unknown 4L80E that is supposed to be rebuilt. Has anyone heard about having a TH400 rebuilt with a taller third gear? A mechanic here in town says that would be my best bet. Not looking for a lot more top end, but I would like to see some drop in rpms. It would still be spendy, but at least I would know what I had.

Anyone know of a cheap GV OD? That would be my best bet.

 

[MadOgre]

onelucky, I am thinking you may be right. I can get 13mpg with it as is with the TH400, and I really don't see getting much better than 15 with this pig even with od. I am into the 91 sub $250 and I am sure I can make money on all the parts. My TH400 works absolutely perfect as well, I kinda hate to ax it for an unknown 4L80E that is supposed to be rebuilt. Has anyone heard about having a TH400 rebuilt with a taller third gear? A mechanic here in town says that would be my best bet. Not looking for a lot more top end, but I would like to see some drop in rpms. It would still be spendy, but at least I would know what I had.

Anyone know of a cheap GV OD? That would be my best bet.

I would check into getting a lock up set up put in to it.

 

[blueburb]

Does someone make a lockup tc for it

 

[marks86]

a 4l80e is the best Chevy transmission option ever made for a square body, and like I said before swapping under the dash harness takes about two hours and is all plug and play

 

[Green79Scottsdale]

I am not sure what Transmission you have in the burb as of right now, but most likely either a TH350, or a 700R4.

This is key IMO. Make sure what you really have! You said yourself you are not a GM guy. Is your donor Burb a 1/2 or 3/4 (or 1) ton? If it's a 1/2 ton, you have a 700R4. If it's 3/4 or 1 ton, you have the 4L80.

How much do you actually drive the Burb? Daily, or occasional? If it's a DD, this swap has merit. If it's occasional, you may not see the cost recovery for a long time. I have gone over this scenario many times with my TH400 equipped truck.

 

[blueburb]

They are both 2500 3/4 tons. I am positive the 91 is a 4l80E. It has a big round plug on the driver side with lots of wires. The burb is a daily, but mostly around town with a 100 mile round trip maybe twice a month, and a longer 400 mile trip maybe once or twice a year.

The deal is that we have an 89 grand marquis that is in mint condition, but it has almost 200k on it, its tired, and I would like to phase it out. But the poor old Mercury still gets 18-23 mpg on a regular basis, and I was hoping to be able to get maybe 15 mpg or so out of the Burb on the open road if possible. If I could get a little better, I wouldn't mind just having the Burb and getting rid of the car. I'm starting to think just keep the TH400, accept the fact that it gets 10-13 mpg, and just keep the car till she blows up or quits shifting.

 

[oneluckypops]

You really think so? He apparently has the complete donor, so besides the trans swap itself, it's just and engine and dash harness swap. No tracking down any parts and the body harness should stay. Seems time consuming, yet simple to me.

Yea I do indeed think its more work then its worth, especially after finding out he already has a TH400.

Why not just swap the engines? or is there something else wrong twith the 91 that were not aware of?

 

[Green79Scottsdale]

They are both 2500 3/4 tons. I am positive the 91 is a 4l80E. It has a big round plug on the driver side with lots of wires. The burb is a daily, but mostly around town with a 100 mile round trip maybe twice a month, and a longer 400 mile trip maybe once or twice a year.

The deal is that we have an 89 grand marquis that is in mint condition, but it has almost 200k on it, its tired, and I would like to phase it out. But the poor old Mercury still gets 18-23 mpg on a regular basis, and I was hoping to be able to get maybe 15 mpg or so out of the Burb on the open road if possible. If I could get a little better, I wouldn't mind just having the Burb and getting rid of the car. I'm starting to think just keep the TH400, accept the fact that it gets 10-13 mpg, and just keep the car till she blows up or quits shifting.

I would start taking the parts off the donor and get them ready for the swap. Once you have everything start doing the necessary steps to your DD, without completely taking it out of commission, to get this swap done. I would think a long weekend would be good to get the trans swapped and it driveable again. Then you can button up all of the other things as you drive it.

I am with bucket, this swap has merit, but only if you are going to keep the Burb for a while. If you are going to get rid of it in three years, then I agree with OLP, this swap probably ain't worth it. I do not see this swap increasing the resale value either when it does come time to sell it.

 

[MadOgre]

All valid points so far.

Im sure anybody with a square would almost be willing to give their left nut for a good working 4L80 installed in there square.

 

[marks86]

All valid points so far.

Im sure anybody with a square would almost be willing to give their left nut for a good working 4L80 installed in there square.

ands theres a good reason we'd give our left nut for a 4l80e in said square

 

[DoubleDingo]

I have a 4L80e but need some parts before I can do the swap. Vortec 350, a torquey cam, 4:10's and an OD will be so sweet!

 

[MadOgre]

Sure would!

 

[Green79Scottsdale]

Im sure anybody with a square would almost be willing to give their left nut for a good working 4L80 installed in there square.

I would do it in a heartbeat! But I would not give me left nut...

I have been thinking 6L80E or possibly Allison lately. Both would be way more involved than a 4L80E, so that is at the top of my list.

 

[MadOgre]

How about the right one ?

 

[marks86]

How about the right one ?

or the main shaft?