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LT1 swap into an 87 Brougham.

50K views 296 replies 28 participants last post by  outsider 
#1 ·
This summer I am going to begin the process of swapping the drive train from my 95 fleetwood into my 87 Brougham. The Olds 307 in the 87 is getting pretty worn out and my 95's frame and floors are rotting out pretty fast...I am keeping the LT1 stock, but will replace all of the gaskets and seals. The engine runs great but I have noticed a little oil dripping down the front.

So here are my questions:

I will swap the engine, transmission, rear end in.

For the rear end: What kind of modifications will I need to do to get the rear from the 95 onto the 87? Will it bolt in? What about suspension parts? Use the suspension from the 87 or 95?

Transmission: Will the shifter from the 87 work right with the 95's tranny? What about the tranny mounting hardware? Will I need to take the cross member from the 95 over and will that bolt on to the 87's frame?

I will keep the 95's computer. How will the AC/Heater controls work? Do those get wired into the computer? I have never dealt with that stuff in the past so I just want to be sure it will still work.


For the drive shaft I have heard you must modify the drive shaft. Anyone have any info on that process? I know you have to have a shop do it but how do I measure for the length needed?

Any other stuff I should be aware of going into this? Aside from any naysayers telling me to just rebuild the tired old 307 ;)

Thanks for any input.
 
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#2 ·
Nice swap. Always wanted to do one myself. I'm on lunch so I'll reply more when I get home if the questions haven't been answered. The frame is exactly the same so your only issues are going to be anything going from the body to the drive train like tranny linkage and wiring. Can't wait to see how you do the wiring. Do you have the service manual for the 95?
 
#5 ·
I can't help much either, but I do recall some here doing a lt1 swap into an early 80's coupe. He went a little different though, he swapped the body and left the LT1 drive train together on it's original frame. It seemed to be a simpler approach if you have the equipment available.
 
#6 ·
Only difference with the frame is the LT1 frame has a dimple where the AC compressor fits. You can either cut/weld your 87, or heat with the torch and beat the crap out of it with a 3lb.

You need the mounts from the 95 for the LT1. Rear end will bolt in. Driveshaft from the LT1 will work fine. Use the LT1 trans crossmember, you may need to extend the ends for your frame. Use the complete engine wiring harness for the LT1. Start at the PCM, and just fold it back up over the engine to the passenger side, disconnecting as you go. AIR, coil, ICM, injectors, temp sensor, etc, etc. Once all done, disconnect the harness from the firewall under the heater hoses. All you'll need to do is figure out what wires need power for the PCM (and there aren't many). I've got a complete spare LT1 Cadillac harness here if you need/break something.

To get the HVAC controls to work, you are going to need to study wiring diagrams. What needs power, grounding, and what sensors need to be read. You should be able to pull those sensors from the 307 and put them in the LT1.

One more thing you haven't mentioned: fuel system. Use the complete system from the LT1. Back to front. Tank, lines, everything. Swap it all over.

If you really like wiring/swapping, you could put ABS/Traction control on the 87 ;)
 
#8 ·
The rear end will bolt up with no problems, the e-brake cable may have a different connector on the end. The 95 rear end will have an extra electrical connector(or hole if you take the sensor out) for ABS but the brake lines will bolt right up. I cut the wires from the sensor and left the sensor in place, works good for filling the rear.

Is the tranny linkage on the 95 a cable shifter? If it is, you may be swapping the steering column at the worst. Dont quote me on that because I'm not sure how or where the cable shift linkage mounts to...or if it even has cable shifter. I bet that you could even swap over the hardware to keep the hard tranny linkage. The 700R4 tranny mount is about 5 inches forward of where the 200R4 tranny mount is, you'll probably need the 95 crossmember, I believe you may have to drill one hole in the frame to bolt the crossmember in but thats pretty easy.

The computer...I dont speak that language. Good luck. Its gonna take a few hours in that service manual to decipher where the main power and grounds for the computer are and which sensors you need to keep. Maybe its on the internet somewhere.

The driveshaft from the 95 should bolt right in if you get the motor to sit in the same spot. If you dont, you measure from the rear u-joint to the rear tranny casing but call the shop and see how they want you to measure.

The last two guys had issues with mounting the coolant reservoir because the 95 has a different type of cooling system.

Here is one swap
http://www.cadillacforums.com/forum...985/271782-lt1-engine-swap-into-84-coupe.html

The other
http://www.cadillacforums.com/forum...leetwood-1985/269483-new-caddys-n-forums.html
 
#12 ·
Well FWIW, I installed a 4L60E from a 1999 truck in my 87 and I used the same linkage that I had but I had to bend it and maybe shorten the horizontal rod from what I remember. It wasn`t hard to bend but as they say, measure 7 times, cut or bend once. I also had to put my linkage end thingie from the 200r4 to the 4L60E. There is a bit of bind when I go to 2nd and to 1st but it`s ok, I never use these slots on the column. Worst case I would have to take it out of overdrive. I don`t know when it`s going to happen though with 3.73 gears

I don't know about LT1s but in my car I used a 1999 5.3 Vortec and I also had to bend the acceleratol pedal so I could use the stock cable from the 5.3, or was it from the 307. I am 80% sure it was the accelerator cable from the 5.3

What are you doing for the speedo. On the 4L60 that you will use does it have the cable or is it electronic? I wanted to use the cable so since the 4L60E had an electronic speedo I had to buy the kit from jagsthatrun.com It was kind of expensive but I`d rather use the speedo cable and not the box
 
#15 ·
Hello i am in the process of that exact swap into a 1984 fwb. I connected the stock trans linkage to the 4l60 trans and mine works just fine.I also used the stock transmission crossmember cause the lt1 crossmember will not fit,the floorpans are different in both cars.the rearend is also a bolt in with no problem only difference is the lug nut studs are metric...good luck hope this helps!!
 
#19 ·
I have a 9C1 rear end in my 1987 that I just finished instaling and the wheels interfere with the rear calipers. Got to get new wheels. I have the black aluminum 15x6 wheels. Good reason to get some 15x7s with 255-70-r15 tires:)

EDIT...I thought we were also talking about rear discs...I misunderstood
 
#22 ·


The swap has begun. So far so good, I got the wiring harness all disconnected and pulled off to the side. I pulled the fuel rail off of the engine instead of disconnecting the fuel lines. Is that a good thing to do? I figure I'll have to take the whole fuel system with me anyways so I'll just keep it attached to the fuel lines and swap it all in.

Couple of questions. For the AC...do I have to drain the system? If so, how do I go about that? I did it once when I was young and dumb just by depressing the check valve and spraying the cooling stuff all over the place but I'm sure that's not the right way. If it doesn't need to be drained can someone tell me how to go about disconnecting it for removal?

I noticed a lot of the hoses and stuff were dry rotted so I'll be replacing most of those.

Can't wait to make more progress!
 
#25 ·
I'm not sure yet...I'll either just heat it up and beat it with a hammer to dent it if it only needs a little...or cut a notch out, flip the cut out part upside down, and weld it back in like that?

We'll have to see when I get to that part of the install. Hadn't thought of that!
 
#26 ·
Cut, flip, weld. It needs a big dent.

Yes, leave the compressor there when you yank the engine. You need to remove the cats, too, the engine will not come out with them on the manifolds (speaking from personal experience, tried to save time on my second LT1 pull, ended up sawzalling...)
 
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