The Stovebolt Site Forums The Shop Area The HiPo Shop Front suspension swap ???

I have been looking for any post involving swapping a "71 front crossmember and suspension into an AD truck and can find nothing.
I'm sure I have read something on this in the past. Can anyone point me in the right direction or provide any info.

Thanks Richard

I'm considering such a swap into my 59 Burb when I install the 500 Caddy running gear, using a 3/4 ton crossmember and suspension, including the disc brakes and power steering gear. It's going to require narrowing the crossmember a little, and a corresponding shortening of the relay rod from the steering gear to the idler arm. I'll also have to fabricate frame mounting points for both of those items. I've done all this while building dirt track race car frames, so it's nothing out of the ordinary, but you'll need to have an extensive knowledge of steering system geometry and a pretty sophisticated fabrication shop and wheel alignment equipment to do it right.
Jerry

Richard,go to User List at the top of the page.Find 49chevyman,he has about 100 posts,look in his Web Shots,you will find what you are looking for.

Thanks for the info.
That is exactly what I had been looking for.
As usual the more I learn the less I know.
This opens up many more questions.
Time to get the tape measure out and do some checking.
Initial measurements indicated that both had about the same track width at 62-62.5 but measuring was under less than ideal conditions. The '71 setting in the tall grass with flat tires didn't help and measureing the rear of the AD assuming the front would be close probably leaves some room for error too.
Any way this sounds like a reasonable option since I already have the donor.

Is there any one out there that has done this with a 46 or earlier. I' tinking about trying such a swap on a 46 one ton useing the later model 3/4 ton ifs. I've done the search thing and found stuff for S10 and car clips , but would rather use something a little heavier as the old truck is used for some light duty towing.

Sometimes you can be too specific in your search, and thus miss threads with lots of information.

The IFS design you are referring to is essentially the same from '63 through '87 and even later on full size Blazers and Suburbans. '71 happens to be the first year they had disk brakes. Much of the information you'll see will say '73 to '87. The design was used more years on both ends.

Mobileortho and Weeds amoung others have both posted pictures of this swap. Steve Andereggen Jr has posted some information and a link to his article on the swap. Joe Way used to post here but I've not seen him in a while, if you can find his pictures online his 3/4-ton swap seems to have come out very nice.

I'm working on the same swap for my '55 1st GMC 1-ton and have started a few threads on the subject. I'm using the IFS from a '72 C20 on mine. I've posted some pictures, but don't think I've updated recently with photos of my suspension mounts. I'll probably do that once I complete getting the steering box in place.

Limiting the discussion just to AD trucks, the frame design is different enough between 1/2-, 3/4- and 1-ton trucks that you really want to be sure you're getting detailed information correct for your truck.

I've crawled under a number of trucks with this swap and have photographed how they were done. Some of them frankly scare me and I would prefer then never be on the road. Others appear very well thought out and professionally executed.

Based on my own research, including talking to one guy who made the swap about ten years ago and who has driven the truck tens of thousands of miles, this is a workable swap that can result in a very drivable truck.

BUT you need to understand the limitations of this approach and its only right for you if it matches what you are trying to accomplish. My own opinion is that this is the wrong way to build a lowered truck. If that is your objective there are much better options. If you don't mind stock height and want a truck when you are finished, this is one of the better answers.

One more tip based on my research: Mounting the steering box in the correct position relative to the IFS is critical. Get it wrong and you will have bump steer worse than any straight axle. The key is to preserve the relationships in each axis with the IFS crossmember.

Those are just my inital thoughts as I looked at your question. This is one of my favorite topics and I'd be delighted to engage further in talking about what I've learned and what others have learned about this approach.

One last tip: When someone tells you how to do it, ask them how many miles they have driven their own truck with the completed swap. While I've yet to drive mine, asking that one question quickly cleared up for me some of the contradictory things I heard from people claiming to know how to do this one.

Are the 1/2 and 3/4t frames the same width in the area involved?
Is there a place on the net to accesss the frame deminsions?
I have a 3/4t AD and a 1/2t 1971 that I would use the ifs from.
I am not really looking for a lowered stance but would like to get somewhere close to the original height of a 1/2t AD.

Thanks for the info

The width is pretty close to the same, and may be exactly the same. However, the surfaces you are bolting the crossmember to are not exactly the same. The various trucks I've measured have all been slightly different.

This IFS crossmember is bolted through the sides to the frame AND bolted through the bottom of the crossmember to the bottom of the frame.

The challenges are in the shape of the bottom of the frame where the crossmember needs to match up and be bolted on. The lower edge of the frame has a complex shape that on a 1-ton is not nearly close to flat. I don't know the exact shape of the smaller trucks, but would encourage anyone thinking about this swap to check it with a straight-edge before assuming this is a simple bolt-on swap. Also be aware most of the surface that needs to match at the bottom is ahead of the axle centerline.

Yes, the 1/2T and 3/4T frames are the same width from the front of the cab forward. The 3/4T frame is 1/4" taller than the 1/2T.

I've done this swap myself. There's alot of debate over it's use because of it's width, but there are ways to work around this. Here's a link to one of my many posts on this subject. You can also checkout my Webshots for more photos.

Everything was fairly simple. I took the crossmember to a shop for the modifications. They shortened it about 1 1/2" and welded everything back together really good. Make sure to measure carefully, then measure again. You won't be able to use the stock engine mounts because they set the engine too low. I had some fabbed by a builder that turned out really well. You can use the tube mount type sold my most classic part suppliers. Choose your wheels carefully. Make sure that you don't get anything too wide as they may stick out too far. I had 16x7 Torq Thrust II's on the front & 17x8 on the rear on most of the photos in my album. I've since went with 17 x 11's on the rear and plan to purchase 17 x 7's for the front.

Do a search here for Joe Way. I came across some of his old posts where he did this awap.There were a couple of articles that helped me. Steve Andereggen Jr. has good info as well as this one
Other than that everything is fairly simple. Hope this helps.

As Steve Andereggen has pointed out and Old Sub mentioned. Measure and remeasure the steering box and idler locations. While the suspension is easy to mount, ensuring the steering is done correctly is the key for the prevention of bump steer.

building templates off the original truck is a good idea.

I actually cut the donor frame to create templates. Keep in mind that frame width is important when mounting the steering box and idler arm.