Suspension question

[Coastie]

So I purchased my M715 earlier this year. I slowly put in a 7.3 IDI diesel with matching manual transmission into the beast. Everything seemed fine until I lowered the truck down to rest on its own feet. The weight of the new engine (which is quite heavy) brought the oil pan down to the front steering cross bar (I know there is a more technical term but I understand theory more than remember names). Was looking at doing a spring over, but I’m not running super huge tires nor want to deal with the cutting/welding/shackle flip rear axle, brake lines, etc. I’m looking to get leaf springs made for the front to replace the old ones in order to hold the heavier weight with maybe a couple inches of lift.

Was thinking about a shackle lift too, but that is just way too much weight to rely on four bolts.

So for the questions… What is the weight ratio front to back on these trucks stock? I’m trying to figure out how much weight each of these springs need to hold in order to prevent excess sag. Also, does anyone see any problems with running taller leaf springs? Everything I've seen on here mainly talk about the spring over.

[randyscycle]

I don't think that the weight of the engine was the problem. People have put 6BT Cummins in these trucks on stock springs. It sounds as if the engine is either sitting lower in the frame, or that the stock springs have had some leaves removed and are much softer.

I have a Big Block Chevy and a TH400 in my truck and I don't think that it even settled 1/2" when I installed it. The engine weighs around 700 lbs by itself with a cast iron intake and cast iron exhaust manifolds and the TH400 probably comes in around 200 lbs or so.

[97XJSP]

the previous owner of my truck built a fairly large front bumper. The weight of the bumper dropped the front end down a bit so he took the truck to a spring shop and they added another leaf to each front pack. I don't see why you couldn't do the same thing. You could also get completely new spring packs built instead of just adding a leaf or two. They are usually pretty good about figuring out what springs to use etc. Custom springs can be expensive, but probably still less than doing a proper spring over.

[Barrman]

I would agree that the engine is too low or your front suspension has been softened. How much hood clearance do you have above the engine?

The 7.3 is around 800 pounds, right? A 6BT is 800 pounds and a lot taller. they clear steering parts just fine.

A 6BT is 1200 pounds and with the proper oil pan, clears ok. Do you happen to have a front sump oil pan on the 7.3? That might be the problem.

[powerstroke715]

I have the 7.3 swap completed, I believe dry weight of the engine alone is just about 1000lbs. I had a little sag after about a month, only noticable at the angle of the shackles. I did do a spring over swap and just a shackle flip in the rear. I used the ford cross member for the engine mount. If I did not do the flip, this engine would not have fit. I have the banks turbo kit that puts height to the engine and currently only clears after a 2" body lift

[Mikel]

We just put a Cummins 6BT in a M715. The front suspension only compressed 3/4" (from having no engine!).

[Coastie]

The sump is in the front of the pan. I have just enough clearance underneath the hood to fit the stock air cleaner. The more I'm looking at it I think I will have to do the spring over. Was hoping for an easier alternative.

I have one of the older 7.3's, non-turbo, mechanical pump. I didn't want to deal with a computer. This thing fills the engine compartment. I had to reroute the steering shaft because of the engine width. I think this thing weighs a little more than the 6BT's.

When I first dropped the truck I still had a couple of inches of clearance. After sitting for 24 hours, I came out and saw the front of the oil pan just barely touching one of the steering rods. I still have seven leaf springs so I assume they are still stock and present.

[brute4c]

Just wondering...is this a winch truck?

[osut362]

i have a 92 ford with an non turbo 7.3 i'm saving (in the pasture) for just such a swap. are there any rear sump 7.3's? how about cutting the sump and putting in a shallower bottom to the pan? i have never had a pan off of a 7.3 and the oil pump may be the limiting factor.....al

[Barrman]

According to this, they made both a rear and a front sump:

http://www.diesel-connection.com/doc...nAppNPrice.pdf