Gen 3 Subframe Mod

[javve]

I have done quite a bit of looking through different threads trying to get all the bits and pieces of info that would be needed to do this mod. I think I have everything but I am sure there is a good chance I am missing something. My goal is to get enough info here to make it worth a sticky. I think I may tackle this when I go to do a 3.2 swap in my mtx. Seems some parts are easier to do without the motor inside.


Advantages:
Better suspension geometry (control arms), the awesome Gen3 ZF steering rack, and bolt-in (as opposed to the stock Gen1/2 pressed-in) front bearings. Ride and handling are improved, brake squat and front end lift at launch are reduced, torque steer is reduced, wheel bearings are easier to change, suspension bushings are easier to change and less expensive
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Parts:
96-97 SLO:
subframe (easiest to modify)
spindles
control arms and knuckles
swaybar (or just the mounts)
outer tie rod ends
ABS sensors.

96-99 SHO:
steering rack with pressure & return hose
Gen3 rack bolts (they are longer)

Another thing to think about is that you will have to make your mounts for the power steering cooler and the cruise control actuator. Also, the area around the lower radator hose and AC line that runs through there is a bit tight.

Use existing Struts & Motor Mounts
The modified pressure line for the gen 3 power steering rack consists of the pump side of a gen 2 line and the rack side of a gen 3 line… or put the Gen 3 rack fitting on the end of the Gen 1/2 hose.

The gen3 subframe may need collars on the swaybars (your mileage may vary). The stock bar has that, but they dont have a 24mm. So if you use a gen2 24mm bar you may need to use collars. on the '96-'97 you have to raise the level of the subframe where you drill the new hole to prep it for the new mount 5/8”. put a couple of the washers from the front axle nuts between thesubframe and the motor mount. Some of the 96/97 subframes do not have a divot where you need to move the front mount location so washers are not necessary.

Gen3 steering rack bolts are what are holding the rack onto the Gen3 subframe you will need - you just retain those as they are longer than the Gen2 parts.

On early Gen3 setups, the sway bar had a collar on the outside of each of the mounting bushings (actually, the bar was upset there to be larger diameter) so that the bar could not move side-to-side since the larger diameter would not fit through the mount. Most of us doing Gen3 conversions have used standard Gen2 sway bars with no issues of the bar wanting to wander side to side.

It's easy to see if you need the collars. With both front wheels off the ground see if you can push the bar left to right, right to left.

You need to relocate is the front motor mount hole 2" left and may need to space it up about 5/8"

To put the Gen3 subframe into a mtx car, you need to relocate the trans mount forward, notch the subframe tube for the transmission, and space up the front motor mount location about 5/8".

For the later subframes, take a hole saw through it where the motor mount needs to be (2-2 1/2"), and then weld a 1/4" plate on top that fits in that odd shaped recess. Should take care of it.

If Doing the gen 3 brake modification at the same time:
For a 94-95 Sho, need FN74 Bracket
Brakes and Rotors for a 96 SHO
 
Courtesy of rubydist

 

 

 

according to AllData (Torque Specs):

control arm rear bolts 72-97 lb-ft
front bolt 57-75 lb-ft
lower ball joint 50-67 lb-ft
lug nuts 85-104 lb-ft
stabilizer bar brackets 22-29 lb-ft
rack bolts 85-99 lb-ft
stabilizer bar endlinks - 57-75 lb-ft at strut, 35-46 lb-ft at bar (??)
front hub to knuckle - 61-78 lb-ft
tie rod end 35-46 lb-ft
caliper anchor bracket bolts - 65-87 lb-ft
axle nut 179-203 lb-ft
front knuckle pinch bolt 72-97 lb-ft

Torque the control arm to subframe bolts with the full weight of the car on that corner of the suspension (jack the underside of the control arm, near the balljoint, up until it just lifts off the nearest jackstand).

 

[jelloslug]

I don't think the collars on the sway bar are necessary. The sway bar on the 1st and 2nd gens does not wander around so there is no real need to do anything different when putting it on a 3rd gen subframe. On some of the 96 and may be 97 subframes the front mount is already at the correct height but you still need to redrill. If there is a big divot where the front mount goes you will need a 5/8" plate to bring the mount up, if it's flat you don't need the plate. The '99 (and possibly newer) subframes have larger mounting bolts for the lower control arm and therefor have different lower control arms. Keep this in mind when you are looking for parts.

 

[kevinspann]

From what I've seen, later gen3/4 sway bars don't even have the collars.

You don't have to do the Gen 3 ZF rack, the gen 2 rack will be fine - you do need gen 3 rack bolts and outer tie rod ends.

 

[rubydist]

1. I did not put collars on the sway bar when I did mine, and all is well. the collars may be recommended, but they are not required.

2. one does not need the 96 caliper to do the 96 brake upgrade - the 94/95 caliper works just fine with the FN74 bracket and the 96 rotor.

3. one does not need to change the rack - the Gen2 rack will bolt right on to the Gen3 subframe with the longer Gen3 bolts, and then there is no hose issue.

why would you do this?
ride and handling are improved, brake squat and front end lift at launch are reduced, torque steer is reduced, wheel bearings are easier to change, suspension bushings are easier to change and less expensive, etc. etc.

 

[Sho Amo]

Kudos to you for compiling all that information.

Very good job!

 

[jelloslug]

Even though you don't NEED to put the ZF rack in it's a great upgrade.

 

[javve]

1. I did not put collars on the sway bar when I did mine, and all is well. the collars may be recommended, but they are not required.

2. one does not need the 96 caliper to do the 96 brake upgrade - the 94/95 caliper works just fine with the FN74 bracket and the 96 rotor.

3. one does not need to change the rack - the Gen2 rack will bolt right on to the Gen3 subframe with the longer Gen3 bolts, and then there is no hose issue.

why would you do this?
ride and handling are improved, brake squat and front end lift at launch are reduced, torque steer is reduced, wheel bearings are easier to change, suspension bushings are easier to change and less expensive, etc. etc.

Kudos to you for compiling all that information.

Very good job!

Thank you and thanks for the info. I'll remove the caliper from the list. I'll add optional to the calipers since some have said they did use them and others did not. I know the Gen 3 rack isn't required but is a nice upgrade, and since going through all that work it isn't much more to add that.

 

[jelloslug]

Another thing to think about is that you will have to make your mounts for the power steering cooler and the cruise control actuator. Also, the area around the lower radator hose and AC line that runs through there is a bit tight.

 

[ohioshodude]

where would one get new gen III steering rack bolts? i am in need of some as i am keeping my rack stock. thanks!

 

[jelloslug]

where would one get new gen III steering rack bolts? i am in need of some as i am keeping my rack stock. thanks!

I just got some long grade 8 bolts and nuts.

 

[boat]

What is meant by the "collars"?

 

[rubydist]

Gen3 steering rack bolts are what are holding the rack onto the Gen3 subframe you will need - you just retain those as they are longer than the Gen2 parts.

On early Gen3 setups, the sway bar had a collar on the outside of each of the mounting bushings (actually, the bar was upset there to be larger diameter) so that the bar could not move side-to-side since the larger diameter would not fit through the mount. Most of us doing Gen3 conversions have used standard Gen2 sway bars with no issues of the bar wanting to wander side to side.

 

[SHOZ123]

It's easy to see if you need the collars. With both front wheels off the ground see if you can push the bar left to right, right to left.

 

[javve]

I added a few things up top, including a few quotes from below.

Is this worthy of a sticky?

 

[kevinspann]

Any steering rack bolt from 96-04, not just from gen 3 shos will work.

For anyone using the later gen 4 parts, the abs sensor is different, or at least the plug is.

 

[sperold]

Someone sticky this thing. Eventually, we will all need later model subframes, and who is going to remember this stuff.
I don't know about you guys, but I am not real great with the search feature. Usually it is either nothing, or so many entries that you can't read them all.

 

[rubydist]

you just need to search for threads started by rubydist for all the useful stuff.....

 

[Art5]

have some patience and soon you will learn that there is one more way to swap engine and subframe with a lot less work.another 2 weeks or so.

 

[sperold]

Rubidist, you are right. But this thread is still a lot of info in one spot.

 

[vortex2450]

Sticky this!