Hey everyone, I have a 93 GMC Typhoon with 427LSX and twin S366s. I can make a ton of power but I can't get this thing to 60ft better than high 1.4's with a nasty bounce. Here are some video links so you can see what I'm dealing with. I have custom made limiting chains for the front end and a pretty stiff suspension in the back: Calvert split mono leafs 225lb version, Caltracs and Strange "pro-mod" DA shocks..all the way tight. I used to have SA Strange shocks in the back but it did the same thing.






Any ideas from those who walked this AWD path before?

Thanks!

 

The Suspension is unloading as the weight transfers. I am not sure how to fix it for your application though.

Have you spoken to Calvert about it?

 

Strapping the rear might help with that initial bounce. It seems to keep undulating, after the 60'; are all your shocks good? Are you on coils or T bars up front?

 

I know, me neither...it's been frustrating as there is so much info and knowledge for RWD applications, not so much AWD/4WD.

Calvert said to loosen up rear extension/rebound setting to allow for the rear separation they build into their split mono/caltracs design? I'll try it but I'm not seeing any separation in my videos...

 

brand new Strange DA pro mod shocks in the rear and good condition QA1 single adjustable in the front. Although the fronts aren't really doing anything since they're strapped down so tightly.

Coil over conversion in the front...

 

Is it sitting on the rubber bump stops up front, or are they removed?

 

Good question - I had to go look. There are rubber bump stops in front on the frame and they are about an inch away from the lower control arm. With the limiters tight maybe a little closer.

 

How often can you go to the track? Here are some things I would experiment with:

Raising the front 1/2" to 1"
Lower the rear, if possible
Strapping the rear, just lightly; keep it from being able to fully extend the shocks if its gonna bounce. I wouldnt use straps to suck it down, but you might have to to get into the springs enough
Make sure the front shocks are healthy and able to damp the motion
Increase air pressures in the tires, or decrease the pressure in the rear while increasing the front

If it was a 4 link truck I would pull link on the passenger upper, "sucking" the truck down

I can't tell you over the web what she is gonna want, I am not that good, but there's where I would start my tuning sessions if this was my truck or a buddy's truck and I was helping set it up

 

That bump stop is hammered...

 

Wish I could get a camera or two under there on a run and see what's happening in front and back. That bumpstop got hammered when I got it. It was 2" lower in the front and with the front shocks all the way loose it would slam the stops over freeway bumps etc...I even cracked a front fender arch. Had to raise is back up.