4x4 suspension sag/possible lift kit opinions...

[joeydurango]

This is posted over in suspension as well, but not too much traffic so I thought I'd ask where more 4x4/lift kit people hang out:

Doing an LS 5.3/4L60e swap into my 1972 K10. Truck is currently stock height with original springs and bushings. Wanted to keep the truck stock height, but on the 4x4 we're running into problems with front diff clearance. Using the stock transfer case location (therefore engine fore-aft is set), using Pacific Fab's 4x4 LS crossmember (fits great in the truck, but doesn't have enough clearance from diff to crossmember if suspension is even partially compressed). So, we have to increase that xmember-diff distance somehow.

My question is: Judging from the info above and the photo below, what are your folks' opinions on how to best remedy the problem?

1. Spring blocks/spacers/whatever they're called - cheap, easy, but probably some downsides? No heavy-duty off road for this truck - will be a daily driver with light off-road use.

2. Small lift kit - 2" or so. Would like to avoid if at all possible... but if you have a photo of a 2" lift truck, post it up.

3. Curious about opinions on this train of thought: I figure that even though the truck sits pretty nicely right now, 42 years of fatigue on those leaf springs has to mean some sag. So I'm wondering what new stock-height springs and new bushings would do to increase the xmember-diff clearance. Any educated guesses on this, given how the truck sits in the photo? 31" tires in the photo. The current front leaf springs, when the engine is in the truck, are significantly negative arch. Not sure if new stock-height springs are negative arch or flat.

4. Finally, curious about having Alcan up in GJ fab some springs for the truck that are slightly "taller" than a stock spring would be. Pricey though.

Any opinions welcome, especially if you've got experience with this type of thing in particular...

[lowrollin70gmc]

Do you have any pictures of the fit of the crossmember/engine/axle? There may be a way to modify the crossmember to keep your current ride height. Most stock springs have a flat or negative arch to them when at ride height, so you're probably on stock springs still. 2" wouldn't look too much different from stock, but if it's stock you're after I'm sure there's a way to modify the crossmember to make it work.

As far as lifting it, blocks in the front are a big no-no and are actually illegal in many jurisdictions due to the effect they have on braking and handling of the front axle. With that said, it is possible to use a zero rate in the front. It's a 1" piece that bolts into the bottom of the spring pack to get just a hair more height as well as the ability to move the axle fore and aft 1" or 1.5".

[ryanroo]

my K20 has a 2.5 inch front spring and a 3" rear block. if you want to check it out or see it up close let me know. i work in the air park and drive it to town most days.

not the best comparision shot, but it is not to tall so as to be a pain, but clears a little bigger tire and might offer you the clearance you need.



as lowrollin said, i picture of the actual clearance issue would help

[joeydurango]

Once the engine is bolted back in place I'll try to get a photo of the problem area. I'll also try for a good shot of the front springs with normal load on them, for comparison's sake if anyone has a photo of new stock-height springs. I expected that this clearance problem would likely show up, but figured we'd try the original setup first... now my main unknown is how much the original springs have sagged over 42 years and whether new versions would be enough, or if the 2" lift is necessary.

Ryan, thanks! That photo's fine for comparison. I'll hit you up if I want to head up to the airpark... you might know, or even work with, my neighbor Todd. He works at Stone Age, and I could see you working at the same place, given your fabricating skills. Reminds me, I gotta go check on your build thread, see how the monster is coming along...

[ryanroo]

I am just up the road from Stoneage. i'm at Holt Sheet Metal. just send me a message or something and i'll be sure to bring it. not to much has happened on my truck. ive been working on a related side project.

[joeydurango]

Did hours of research and tried to get some measurements on various trucks yesterday to solve this problem. Just for the benefit of anyone facing this same issue later - I don't believe an LS swap with the Pacific Fab crossmember will work in a stock-height 4x4. Nothing wrong with the crossmember, there's just not enough room above the front diff and the crossmember is a pretty tight fit to the pan. Gotta note that Pac Fab DID say that the swap *should* work with a stock height truck with good springs - not what I found at all, see below.

As far as I can tell from research and measurements, the stock front suspension should have about 4" of travel. We're sitting, on original springs, with only about 3/4" clearance between crossmember and diff. I figured out via a few measurements on other trucks that our original springs have sagged about 1 1/2", so if we went with stock new springs, we still would only have 2 1/4" of clearance, not nearly enough for normal suspension travel. End of story (for now): There's a TC 2" lift kit on the way. Should work great, we'll see how it goes in the real world.

User FirebirdJones somehow did this same swap into a stock-height '72 Jimmy, with the same crossmember... all I can figure is that he doesn't have full suspension travel. That's what it looks like in his build thread too - a shot from underneath showing the diff and crossmember has nowhere near 4" of clearance.

[JJH Jimmy]

Would it be possible for you to build some adapter plates that bolt to the engine that would move the engine mount to the back a bit to get the clearance you need.

I have a 4" lift and built my own cross member, but i think that it would have worked at stock ride height. There are people on here that have done it.

If i remember correctly some guys have put their engine in without a cross member. They just built the engine mounts off the side of the frame and i think that the LS engine block was designed to be used this way.

Good luck!

[ryanroo]

Joey,
is this truck parked at mountain mechanical? ive been past there a few times and noticed one. it occurred to me today that it may be yours.

[joeydurango]

You got it! No automotive tools + no garage = no major mechanical work for me. I am a mechanic, just not on cars... I can tinker on the truck and get small projects done, but when it comes to an engine swap I'm sunk. So it's off to our buddies Dave and Phil at MM... although given your experience, had I known you were out in Baytucky before we started this project, I would have seen if you wanted to make some extra cash (and let me pitch in, too).

Also, for someone's future benefit, I checked again and if you were handy at welding AND you were using a low-profile LS oil pan, the Pac Fab xmember does have a little room between it and the pan. Maybe just enough that you could get away with new stock-height springs if you re-worked the xmember (or made your own). Maybe enough... but not enough that I'm confident enough to try it. So it's a 2" lift for this truck.

[ryanroo]

I'm sure those guys are having a blast working on something fun like that! i know i would! i am certainly interested to see how it turns out. its a swap i've considered many times in my old beater.

that thing will be one heck of nice truck with the new powertrain. if you think there's a way i can help out just let me know.

[WhiteWhale]

Originally Posted by ryanroo

my K20 has a 2.5 inch front spring and a 3" rear block. if you want to check it out or see it up close let me know. i work in the air park and drive it to town most days.

not the best comparision shot, but it is not to tall so as to be a pain, but clears a little bigger tire and might offer you the clearance you need.



as lowrollin said, i picture of the actual clearance issue would help

Looks great! What company did you go with for the lift? What size tires and rims?

[imjeff]

Go with a 4" springs all around. Simple and looks good!

[ryanroo]

Originally Posted by WhiteWhale

Looks great! What company did you go with for the lift? What size tires and rims?

Thanks.

the front springs are tough country. the rears are stockers with a 3" block i had laying around.

rims are 16"x 6.5" i think. tires are 285-65/16 basically a 33x10.5/16