I recently aquired a '79 half ton GMC, and I want to run some 42's. I was hoping that someone might give me some advice on how high i need to go. Fender trimming is not an issue. I am willing to cut as much of the fenders as it takes. Any help would be appreciated.

Depends on allot of things. Wheel width, back spacing, which "42"s, how flexy the springs are, what type of wheeling (mall cruising, mud, and rocks all have different requirements for clearing the same tire - if your here, doubt it's mall cruising). Also, do you have a body lift? Worn stock body mounts? Willing to move the axle forward? Just exactly how much you want to cut and modify? If you run primarily mud and don’t need allot of flex, you can run a relatively stiff suspension and less lift. That’s the sort of thing you gotta think about.

Me, I'm running 42s on 15x8 wheels with 4” backspacing and a 4" BDS lift with no body lift but good factory mounts. I currently have no fenders (although I may add them back seriously modified) and I had to modify (flatten) the fire wall pinch weld plus knocking the part of the firewall closest to the tire back about 2” or so with a 12# sledge. That was enough to make it work, but just barely. Moving the D60 2” forward gave me the room I wanted.

BTW, I’m originally from Florence, AL. Spent roughly 26 years in that area.

I'm running 44 inch boggers on stock 7 inch wide 16.5 rims, six inches lift (approx) with 63 inch chev rear springs on both ends, lots of flex, I have almost nothing left for cab mounts, I had to remove the air ducts on the sides of the cab, then cut and paste a piece into the floor for more clearance, just touches at full stuff.
my front axle is also set forwards 2 inches. my fender lip is moved as far up as possible without removing the body line and as far forwards and back as possible. with 42's and stock length 6 inch lift springs I'm sure you could get away with lots of clearancing.

I'm running 40x15" swampers on 16.5X9 rims with 6 in lift and a good amount of fender triming.

Thanks for the help guys. Im thinking about going with a fairly flexible 6 inch spring. When you say you moved the axle foward, how did you do this? Did you move the mounts, use a longer spring, or use a spring with a shorter front side. Thanks for the help. I am a Chevy virgin, grew up on Landcruisers.

I remounted my springs forwards two inches when I did the spring swap, this is the best way in my opinion, the truck I have even had holes up front where the stock perch could be remounted for this.

I was going to move the springs but, I also wanted to reduce the front overhang to improve the approach angle. So, I built some offset plates out of 3/4 x 3 bar stock. These were trimmed (actually needed to be about 2.75 wide to fit right) and bolted into the spring pack using grade 8 bolts recessed into the plates. Then 1/2 hardened steel pins were put in place and tacked at the proper location (2” offset). They are longer than normal offset plates (also longer than the perch) to stabilize the spring at the original hole which was getting close to the end of the perch. When I’m done with the frame horn and core support mods, I’ll have almost exactly 90* approach angle with leaf springs. Maybe just a little more…

BTW, this is a trail only rig. I wouldn’t have done it this way for a dual purpose daily driver. This should not exhibit the same problems as “front blocks” due to the bolt in design and it should be safe, but, I don’t take chances on the front axle location and attachment. Approach angle is just not worth it to me even for the small degree of risk that (I believe) is introduced.

Heres a chart I came across, might be helpful in deciding tire size vs lift, it also has a link for tire size vs. gears, its worth looking at.
http://www.4wheelparts.com/Tirefitmentguide.asp

Do you have any pictures of your truck set up like this?

Ken H.


Originally posted by mytzlflick
I'm running 44 inch boggers on stock 7 inch wide 16.5 rims, six inches lift (approx) with 63 inch chev rear springs on both ends, lots of flex, I have almost nothing left for cab mounts, I had to remove the air ducts on the sides of the cab, then cut and paste a piece into the floor for more clearance, just touches at full stuff.
my front axle is also set forwards 2 inches. my fender lip is moved as far up as possible without removing the body line and as far forwards and back as possible. with 42's and stock length 6 inch lift springs I'm sure you could get away with lots of clearancing.

My old truck was an 80' K30. 4" Skyjackers with blocks in the back. (Read that as little to no flex :flipoff2:) I trimmed the hell out of the fenders and put in 42's with out too much trouble. The front axle was still in the stock location and the firewall was flattened / massaged with an 8lb sledge. The tires would rub if I really flexed the truck.

My new rig is a 77' K10 with 1 ton running gear sitting on 6" BDS in front a 4" BDS in the back. I modified the rear perches to be a 2" lift so there is 6" in the back also. I am running 44 TSL's in front and 44 Boggers in back. I have moved the axle 1" forward and also did the same flattening to the front of the cab floor. The front fenders were trimmed a little more than the 80' and I also raised the floor of the radiator support to gain more room at the front edge. I have not ramped this truck but it looks pretty good for tire clearance. The rims are 15 X 12 with 3.5" backspacing.

I run 38's on a 4 " lift with alot of fender cutting.I'm sue I could run 42's with more cutting and a offset front spring set up.The 38's I'm running are 15.50 wide.....12.50 would be alot easier.Anyone have a set of 12.50/38x15's???

10" body lift...;) :skull:

6 in lift and break out the sawzall :D

i say 8 inches.

8" soft front leafs

4" ORD flip in the rear with 4" soft leafs.

i run 6" lift and 40's and I can STUFF them. rubs, but nothing that will even get your attention.

Pic of the rear trim

http://coloradok5.com/gallery/albuq20/aae

pic of the front

http://coloradok5.com/gallery/albuq20/aac

everything was pounded flat

what brand soft springs do you suggest, and 63" long 4" lift out back?

http://www.pirate4x4.com/readersrigz/reader620.jpg
i hope this pic works?

Nice job on that fender opening. I like it. I see that you also ditched the bed like I did. I just tossed the front fenders too...

I ran it that weekend without a passenger side fender cause it wasn't finished up yet but I really like the way it looks with fenders. plus I may pick up a few small time sponsors up here for a competition or two so looking good is important too.
yeah the bed was going to be wayy more work than it was worth and the blue box is waterproof and only cost $20 so that made for an easy decision there.
the biggest challenge on mine was clearancing the firewall. I have a motorcycle cooling fan to make the heat work cause the stock air ducts are missing along with a sizable peice of floor.
I still want to lower it another 4 inches though.

8" suspention+3" body = tire rub when tires are turned on the fenders of my friends 81 chev with 38;s so fender cutting is in the equation.:D to keep it as a lower center of gravity

Originally posted by BLUESMAN
Anyone have a set of 12.50/38x15's???

I do. 4 + 3 and mild trimming. They still rub. I need more lift!

I do really like Mytzlflick's fenders though. Mind if I copy em? :D
I need inner fenders though, I'm a bogger....

copy away
I have a few suggestions though, first do the welding on the truck not on the bench, mine fit perfect till I welded them got a lot more warpage than I expected.
I plan to make inners as well as there is a lot of mud here. I was planning to use sheet aluminum for that though, run it straight up from the framerails to just shy of the hood to seal it up there. the stock inners are definitly not gonna fit with my fenders.
oh yeah they look better painted too!

Cool.

Yeah, my inners don't do a very good job of keeping the engine clean :(

Tell me more about your frame extension dealie and with that kind of shackle angle, is the ride affected? Or with 44"s can you even tell......

Hey mytzlflick,
what did you do in the rear to put those 63" springs in?
I have been thinking about putting some in the back of my truck and am curious how much they will sag.
I have stock springs now as well as a shackle flip in the rear.
If I just moved the front and rear hangers out would I end up with the same lift as I have right now? I could always move the front hanger down some but I just want to know how much.

reddwarf: the frame extension was originally built with 2 inch box tubing (old receiver hitch) just comes out ten inches from the front mounts as the original front of the frame had been butchered in a previous life. the spring hangers are rear spring forward hangers that came with the springs from the wrecker mounted down around 6 inches lower and 4 inches or so forwards from stock (I can measure it if you really need to know cause I can't remember now). the shackles in the rear are an experiment that works fine. rather than remount the hangers themselves I figured a high shackle angle might be ok. the springs flex fine, incredibly soft ride really ( I originally ran it with 33's for maybe an hour). as an added bonus they hang almost straight down at full droop adding in another few inches of travel.

triaged: same deal as the fronts, took a stock hanger as the start point, cut it to weld in a piece of 3x3 box steel for the stand, welded that to the frame (not my first choice but this is the testing ideas truck and will be redone this winter) in the rear I used two pieces of plate (I was out of stock hanger brackets) and the stock shackles lengthened a bit and boxed in compression. rear flex without the box and with all my tools is a little less than the front. I will probably try without the overload leaf if I stay with this setup (I am eyeing four link setups to fix my turning problems) the amount of arch will depend on how much weight you carry and how think your springs are now, my original springs didn't move at all when I pulled the box. again if you really need to know i can measure the height of the springs installed.

mytzflick,
good job on the fender trimming.It certainly is not the common hack job seen when it comes to chevy fender trimming..Kinda curious how strong of a motor your running and if you have any problems with axle wrap in the front or back with such flexible springs?:D

unfortunatly I have a stock 350, maybe 250hp. enough to spin the rear tires ok but in 4wd no where near enough power. definitly looking for a big block to swap in.
wfo in 2wd to the rev limiter, let go of the clutch, the rear tires will wrinkle under power, looks real nice. not a bit of hop at all. the springs are flexible but very strong, guys watching say they can't see any evidence of spring wrap.

yeah the fender definitly came out nicer than I was expecting. can't wait to fill the welds and paint the thing.

thanx for the reply.