1998 Pontiac Grand Prix RWD Swap


FireFox05
02-12-2008, 10:56 PM
Alright gents, so my ride is a 98 Grand Prix GTP. However, I have always wanted a Trans Am. But I love my GP, the looks of it, it's a sedan so I love the four doors.... So I'm going to make a fusion of the two cars I want.

Now, before you go calling BS or waving flags at me, here's a thread (http://www.clubgp.com/newforum/tm.asp?m=3776377&p=1&tmode=1&smode=1) of a %60 complete swap, and there is one GP out there with a Grand National engine and rwd swap done by a pro shop.

Now, as you can see from some of the pics in that thread, there is a TON of room in that engine bay, more than enough for a V8. My idea is to get an LT1 with the T56 and a Mustang rear end (A big reason is because of the bolt pattern on the axles- matches my fronts). Now, I figure the LT1 will be easy enough to get my hands on, the T56 a little more tricky, but still not bad. I've seen complete dropouts on eBay for under two grand.

Fab work that will have to be done, in a nutshell:

K-Member:
I'm thinking stock F-body here. Positioning and all of the finesse work will be the deciding factor. Also, new lower control arms for the front suspension will be required.
Front steering rack:
Custom mount on the front of the K member? Probably. Keeping the rack down close to the level of the control arms will keep bumpsteer down.
Trans mount:
If you look at the thread I posted, he ended up cutting up a lot of his interior floor to make room for the trans and the mount. I don't know how much room I can gain by pulling the motor forward, but the more the better.
Rear axle mounting:
Doesn't need much explaining, going from no axle to a solid rear axle is a big move. Lots of cutting and fab back here.
Fuel cell / trunk mods:
The stock gas tank is in the way of the drive shaft. Relocate to inside the trunk? Maybe behind the axle?


Now, you're probably asking why I'm posting this over here. You guys know all about f-bodys, obviously. And I know several of you well. So I just want to gather as much input as I can get.

Some notes:
This WILL be a DD car when finished. Stock interior is a must, small modifications can be accepted.
The LT1 (or other motor perhaps, I'm not dead set) will be going in pretty much stock. It's a bit of a boost in power over the stock GTP anyways, and I can always mod later. This allows me to devote as much funds as I can to the actual build.
Small items also will need to be addressed. Exhaust routing, headers to a single pipe and split again seems best, but without a lot of hacking, that central tunnel will get tight fast. Brake booster is addressed in the posted thread, but just to say it here, almost any vacuum booster will probably be too large. One person solved this by going to a custom fabbed HydraBoost. I will probably do something similar.
I will say, I'm hesitant to go with the LT1 for one reason: Boost. They don't like it much without a bit of building (if I recall correctly) and I have grown addicted to my suercharger whine.

Thanks for reading guys, the more comments you make (you can skip "You're crazy", "this is a waste of time", "Just get a GTO/f-body/G8" comments) the more ideas I will have.

wrightz28
02-13-2008, 09:25 AM
Well, all I can say is, you've atleast done some homework on it and know some of what you're up against. Ultimately, it's going to to be up to your ability and resources to follow it through, with the right plan, time, knowledge and budget, nothing is impossible.

That said, GM toyed with this idea for a special edition Monte SS 'Intimidator' to commemorate Dale Sr's death. I believe it was Hot Rod that had a extensive write up about how they planned to go about it, and I if I remember correctly, they did get the prototype done and you may want to look for that. It was also based off a Australian version. The car never came to frutition due to costs and thus the idea matured into the new GTO.

Good luck :thumbsup:

FireFox05
02-13-2008, 12:37 PM
GM also tried an LS1 prototype with AWD known only as the "G8". However the idea was scrapped because of the fact that the AWD they retrofitted was from the Aztek, and couldn't handle the power the LS1 was putting out. I forget when this was, 02 or 03 maybe? Every once in a while it will show up at a large Pontiac gathering.

My biggest challenger will be firming up the framework of the unibody once I cut out so much of the rear center section.

Also, just to be clear, I will be doing this on a dummy chassis, not my car. So I won't be out of my DD while this project is going on. I'll just swap everything over once it's done. Or maybe put a custom interior in and sell mine outright. *shrug*

stieh2000
02-13-2008, 03:28 PM
This will be such a sweet car when its done. If it only wasnt so damn tricky/costly to do this. And why stop at an LT1, try for an LS1. May be more upfront, but the potential with modding will blow away the LT1. :2cents:

Good luck with it! Cant wait to see it finnished.

gmack221
02-13-2008, 04:06 PM
Maybe I'm missing the big picture here, but it seems like your going to have to cut up most of the car to achieve what your building, trans tunnel, driveshaft tunnel, subframe in the rear to mount the rear axle to (which will make it ride higher unless you build it inside the car, which you said you don't want to do b/c its a DD). There will be no good place to route the exhaust, to make the trans tunnel your going to have to cut away part of the firewall which might cause problems with the dash / under dash pannels. On top of all of that your pretty much going to have to frankenstien the wiring harness (days & days of work). All this so you can have a 4 door rear wheel drive daily commuter. With all that said if its your dream ride by all means have at it.

But if cost is the only reason for such a creation you might want to consider a different donor vehicle for the creation. Might I suggest finding something that has been wrecked in a rear wheel drive 4 door car, maybe something someone has already parted out the engine & trans but has a title. If you take this route make sure you look into what it takes to convert a salvage title to a rebuilt title in your area. The reason I suggest wrecked is if you can do that much fab work, you can rebuild / replace parts on a wrecked car cheaper then you can buy the metal to fab up the car you are talking about building. The interior will already be set up for rear wheel drive (some added metal for strength in the rear end might be necessary), but the floor plan will have room for a rear axle, the gas tank will not be in the way, and a rear wheel drive car should have a stronger subframe which will keep the car from twisting & the doors fitting nice. There's alot more that goes into engineering the platform of a car then one might think.

Good luck with whatever you decide to do, I'm just having a hard time seeing the ride height you want without tearing up the interior of the vehicle.

Firebirdlad03
02-13-2008, 05:14 PM
Well it sounds like alot of work. but i too think it would be sweet when its done. Sure you can can find other v-8 rwd 4 doors. but not a grand prix. so i support ya, like wright said. nothing is impossible

philly rs
02-13-2008, 05:59 PM
thats alot of damn work and money that could be spent on a lexus or a benz!! hell why do u want a rear wheel drive grand prix?? the supercharged ones are bad ass the way they sit, my boys wife has one..he even modded out the blower.... the cash flow u are gonna spend why not get a nice 2002 ss??? now how bad assed is that???? huh?? huh??? cum on u know u feel it:grinyes: :grinyes:

FireFox05
02-14-2008, 09:29 AM
Well, as far as the motors go, I look at it this way. If I can live without boost (I don't think it'd be a good idea on an LT1), the extra $2k or more I'll save by using the LT1 would get me a nice set of heads and headers for it, and maybe a good cam too. And that right there would net me a good deal of power. So that's what my thought is there. Plus, I can get the T56 AND the LT1 for the price of a decent LS1 alone.

Thanks for the encouragement guys, I really want to do this. The first powerslide will make all the cost and time and effort worthwhile :-p

The plan right now is to focus on getting the extra frame to start hacking on ASAP, then followed by the major parts, rearend and motor/tranny. I'm hoping to suck my Dad into this, father/son project.

Can anyone tell me the name of that site that specializes in LT1 cam/head combos? I can't remember his name, but it was almost a mom/pop type deal.. He had a low budget website with a black/white checkered flag theme.

Edit: Found him! Lloyd Elliot!

FireFox05
02-22-2008, 03:43 PM
Bump.


The biggest thing I am worried about, is what am I going to do if I have to completely cut out the tunnel and make it larger? Without destroying the interior of the car. Thoughts? Tonight I'll post the pics of one of the existing swap projects here, so you can see them easier.

blindeyed
02-22-2008, 04:21 PM
Just to see what you're up against, I would suggest you check out this thread on another forum:
http://www.fullthrottlev6.com/forums/showthread.php?t=29604

There's an crap load of custom parts that have to be made in order for the swap to work. There is also an unbelievable amount of room in that engine bay.

FireFox05
02-26-2008, 09:09 AM
I know, isn't it funny how much room is in there?? Thanks for that thread, I'll check it out after work.

Nicholass1979
02-26-2008, 05:24 PM
my father took a 1958 triumph 10 and leightened/widened the body and put it on a 77 mustang 2 chassis and all the work that went along with it... to me it would almost be more productive to try to mate the body of your car onto the chassis of a buick roadmaster or a caprice etc.. that already has the v8 in it

blindeyed
02-26-2008, 05:56 PM
my father took a 1958 triumph 10 and leightened/widened the body and put it on a 77 mustang 2 chassis and all the work that went along with it... to me it would almost be more productive to try to mate the body of your car onto the chassis of a buick roadmaster or a caprice etc.. that already has the v8 in it
That might be possible if you could remove the body from the chassis, but since its a uni-body (like most all new cars), I don't see that being any more easier than just converting it to RWD.

FireFox05
02-27-2008, 01:18 PM
I don't know about that, I'd think with all the fab work to do all that work, it'd be just as easy as converting my car to RWD, like Jason said.

FireFox05
02-28-2008, 10:48 AM
Hahaha, I just looked at that thread on FTV6 Jason, and that's the same guy and same build as in the link to ClubGP that I posted.

Edit: But the different comments from other people were good to read. So there was some benefit! Thanks.

blindeyed
02-28-2008, 02:49 PM
:lol: Guess it probably would have helped if I checked out the link you posted first

FireFox05
02-29-2008, 09:02 AM
Well, got a small update for this thread. I'm making plans to get my k-member, steering rack, an LS1 and T56 in the next few weeks. Found a totalled 2000 Camaro SS for sale for under two grand with all those parts on it. That's exciting because The cost of a LS1 + T56 dropout with that many miles on it is at least 3 grand. So , this means I need to start looking for a beater to drive during the project.

wrightz28
02-29-2008, 09:11 AM
Well, got a small update for this thread. I'm making plans to get my k-member, steering rack, an LS1 and T56 in the next few weeks. Found a totalled 2000 Camaro SS for sale for under two grand with all those parts on it. That's exciting because The cost of a LS1 + T56 dropout with that many miles on it is at least 3 grand. So , this means I need to start looking for a beater to drive during the project.

NICE find :thumbsup:

FireFox05
02-29-2008, 10:07 AM
NICE find :thumbsup:


Thanks man, I thought so too. I spotted it and I was like *snatches*

Edit: Nevermind. Looks like I'm out of luck.

wrightz28
02-29-2008, 12:19 PM
That sucks, sounded like a very positive opportunity. I had a simlar experience when I bought my '87 Electra Park Ave, sight unseen, my wife wanted it so I had to get it :( Turned out the front end was wrecked and the heads were warped as all heck. So as it was sitting there awaiting a few hundred dollars in parts that were unexpected, we got a phone call from a buddy who just had a customer stiff him on a estimated repair bill for a similar model, "$75 bucks for the title and try to drive it home or tow it". Gimped it home and stripped it for all it was worth.

Hang in ther, another will come along, maybe even better :dunno:

FireFox05
02-29-2008, 01:05 PM
Thanks man, pretty down about it right now.

FireFox05
06-02-2008, 10:43 AM
This project has wings finally!! I'm selling my S/c'd 3800 to a buddy of mine who has the base 3.8, in exchange for borrowing his car (since he has a motorcycle and a truck and his car doesn't get driven much) to drive to work during this project. So this saves me the extra dough of buying a car to drive, or one to hack up.

I made some decisions about what I'm doing, too. I made up my mind on an LS1/T56 combo for the car. Later on down the road I plan on picking up a LMSpeed Magnusen MP112 s/c for it. I also decided to go with a 9" rear end, with high 3.xx gears or maybe 4.10's and a posi diff. I also decided, instead of taking out the center hump of my car and making one custom, to just cut out the trans/driveshaft hump from a camaro and fab that in. Less work in the long run, I think.

So the cutting to my car might happen soon, and I'll post pics when progress is made!!

For thos of you with F-bodies, I could really use a hand. I need to know the distance from the bottom of your K-member to the ground, preferably at stock ride height. Also, from the tailshaft of the trans (t56 preferably here) to the front edge of the k-member. And last but not least, from the highest point on the trans near the shifter to the top of the center armrest console.

THANKS guys!! I'll be back soon!

FireFox05
06-06-2008, 09:28 AM
Nobody?

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