'86 Grand Prix Rehab

justacruzr2

Apprentice
Jun 16, 2017
93
33
Midlothian, Illinois
I've been asked by some of you to post some pix of a project I've been working on so here they are with a little bit of narrative. Here's what's been done so far.

1) left rear trunk floor patched
2) underside of car sandblasted from rear to firewall (everything underneath *)
3) underside primed
4) underside painted
5) underside undercoated (only the body sheetmetal. I'm leaving the frame painted. I've seen some unwanted things, like rust, happen when you undercoat the frame.)
6) all new NiCopp lines installed. This included switching the evap line from the right to the left side and the fuel line from the left to the right and deleting one line. 84' GP has only 3 lines whereas the 86' had 4 lines. 305 has it's fuel line on the right side. This also included all the brake lines from the proportioning valve to the rear brake cylinders plus a new rear brake hose.
7) new proportioning valve
8) new master cylinder
9) new shocks in the back
10) sandblasted and painted the gas tank
11) made a new parking brake cable guide (attached to the drivers side rear floor) because old one had rusted away

What's left to do is install the left rear reinforcement and the frame rail end pieces and then reinstall the gas tank and rear bumper and the new parking brake cables. For the gas tank I have a new sending unit since an '84 has only 2 outlets and an '86 has 3. Installing the reinforcement is the next thing I will be doing. And because somebody is going to ask about those ramps...I built them myself at a cost of about $120 for the materials.

* I did not sandblast the driveshaft or the brace below the transmission yoke since they will be coming off during the engine swap and that's the best time to do that. Also, the trans crossmember is different for the 305 than the 231 so I didn't sandblast that either as I will be using the one from the '84 and that's when I will sandblast and paint that too. Thanks for following.


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pagrunt

Geezer
Sep 14, 2014
6,776
113
Elderton, Pa
Unless you're going from a 3 speed auto to a TH200 4R or just to true duals the transmission crossmember will be the same/similar regardless of it being a 231 or 305. But nice work you have done under your GP.
 
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justacruzr2

Apprentice
Thread starter
Jun 16, 2017
93
33
Midlothian, Illinois
Unless you're going from a 3 speed auto to a TH200 4R or just to true duals the transmission crossmember will be the same/similar regardless of it being a 231 or 305. But nice work you have done under your GP.

I beg to differ with you. The crossmember for the 231 is longer as it goes from the middle mount position on the passenger side to the forward mount position on the drivers side. The 305 crossmember goes from the middle mount position on the passenger side to the middle mount position on the drivers side. Look under your car and you will see 2 mounting positions built into the frame on the left side. Besides,, the crossmember currently on the car is rusted away at the very end on the right side. There's only 1 bolt holding it right now on the right side.
 

pagrunt

Geezer
Sep 14, 2014
6,776
113
Elderton, Pa
I beg to differ with you. The crossmember for the 231 is longer as it goes from the middle mount position on the passenger side to the forward mount position on the drivers side. The 305 crossmember goes from the middle mount position on the passenger side to the middle mount position on the drivers side. Look under your car and you will see 2 mounting positions built into the frame on the left side. Besides,, the crossmember currently on the car is rusted away at the very end on the right side. There's only 1 bolt holding it right now on the right side.

My brother had a '82 GP with a 4.1 & 3 speed & it used the crossmember as my '81. My '81's original frame (now has a '86 SS frame) also had only one mount position per side as the TH200 4R was not an option until '84. If you have the crossmember mounted in the rear most of the two drivers side positions then you shoud have a TH200 4R 4 speed as all aother transmissions-manual & auto 3 speeds- used the front most drivers side positions as pre '84 frames don't have the rear most. I've swapped out too many transmissions in these cars over the years to know that (thanks to my brother, the pro neutral-dropper).
If your pan looks like #5 then you have a TH200 4R unless a previous owner put a TH400 (#4, never was a factory option) & those would need the same crossmember.
1565289233520.png
 

justacruzr2

Apprentice
Thread starter
Jun 16, 2017
93
33
Midlothian, Illinois
My brother had a '82 GP with a 4.1 & 3 speed & it used the crossmember as my '81. My '81's original frame (now has a '86 SS frame) also had only one mount position per side as the TH200 4R was not an option until '84. If you have the crossmember mounted in the rear most of the two drivers side positions then you shoud have a TH200 4R 4 speed as all aother transmissions-manual & auto 3 speeds- used the front most drivers side positions as pre '84 frames don't have the rear most. I've swapped out too many transmissions in these cars over the years to know that (thanks to my brother, the pro neutral-dropper).
If your pan looks like #5 then you have a TH200 4R unless a previous owner put a TH400 (#4, never was a factory option) & those would need the same crossmember.
View attachment 120340

Well, apparently they made a change with the '86 frame as it does have 2 mounting positions on the drivers side and the crossmember is attached to the forward position on the drivers side for the 231 (it's up near the proportioning valve) . Don't know what trans is connected to it since my '84's 305 and THM350C is what's going in it so I will be transferring all of what is required to support that combination into the '86 (engine and trans mounts and crossmember). along with the wiring in the engine compartment and the computer. My '84's crossmember goes from side to side...never noticed whether it had a second (more forward) crossmember mounting position.
 

justacruzr2

Apprentice
Thread starter
Jun 16, 2017
93
33
Midlothian, Illinois
Unless you're going from a 3 speed auto to a TH200 4R or just to true duals the transmission crossmember will be the same/similar regardless of it being a 231 or 305. But nice work you have done under your GP.

I stand corrected. I was under my '84 for the first time in a long time this past weekend to replace the main brake line for the rear brakes and you're right...the crossmember is the same as the '86 with the 231. But there are still 2 mounting positions...one forward and one in the middle. Wonder what engine/trans combo uses that middle one if any.
 

pagrunt

Geezer
Sep 14, 2014
6,776
113
Elderton, Pa
I stand corrected. I was under my '84 for the first time in a long time this past weekend to replace the main brake line for the rear brakes and you're right...the crossmember is the same as the '86 with the 231. But there are still 2 mounting positions...one forward and one in the middle. Wonder what engine/trans combo uses that middle one if any.
The second set of holes that are rearward (the middle) are for cars with a TH200 4R. They have the trans mount pad in a position further back than all three speed auto's except for TH400's/manual's/Powerglides. The crossmember is more straight across than what you have under your car. About '84 the TH200 4R became an option so the '84-'88 frames have the second set of mount holes for it.
 
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justacruzr2

Apprentice
Thread starter
Jun 16, 2017
93
33
Midlothian, Illinois
Sorry that there haven't been any updates so far this year and for good reason. Back on April 20th the work vehicle I was in was t-boned by a person who went thru a red light. It broke my clavicle (collar bone) and I had to have surgery. Right now I am not allowed to do anything heavy. Looks like this summer is shot at this point. Very disappointed.
 
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