BJ74 TD Build Thread - Stoffregen Motorsports

[Stoffregen Motorsports]

Sorry for the delay. Christmas and all that...

Going through my pics, it turns out I am going to have to jump out of sequence a bit. I did not take any pics during the crossmember phase, so you'll see it, but with the front suspension mocked up already.

The crossmember is the most important piece of the link suspension puzzle. It holds up the trans/t-case and locates the front lower links. It's placement is critical. We played around with different designs, but we ended up going with the middle of the road design as far as cost was concerned. It is removable to make transmission R&R easy, but it also locates the links so it had to be bolted in a manner that promised the greatest strength and consistent locating so the suspension won't have to be adjusted after it has been taken out and replaced. We used 5/8 coarse thread grade 8 bolts to locate it and we drilled the frame and welded in sleeves to make it nice and strong.

Drilling the frame for the sleeves.

 

[Stoffregen Motorsports]

Here, the front 3-link is completely mocked up with temporary links. The joints at the axle end are Parts Mike 1.250" flex joints for use with 9/16 bolts. The frame end uses 1.250" Metal Cloak Duroflex joints to keep road noise to a minimum.

The front suspension was designed with a 3 link calculator first using a triangulated orientation. The lower links are pinched at the frame end to make packaging easy and offer the best performace. Tire clearance has been a problem in the past with the lower links closer to parallel, so pinching them assured there would be no tire contact.







Lifting a truck on a two post lift can be challenging after all the brackets are cut off, so I cut a hole in the frame and welded these 2" x .120 wall DOM sleeves. Now there is a solid lifting point that can also be used for future rock slider mounts.

 

[Stoffregen Motorsports]

Using the 25% rule, where the vertical separation between the upper and lower links (on the axle) needs to be 25% of the diameter of the tire, we built some link brackets and welded them up. The lower brackets end up below axle centerline, but with a truck this low, there was no other choice. The upper link joint hit the motor mount at full stuff, so it was cut away and reinforced to give us all the up-travel we could use.

 

[Stoffregen Motorsports]

Here are some pics of the links, brackets, and final mock up.

Axle end panhard bracket.






A modified panhard bracket and custom urethane panhard bushing and sleeve.


Upper link axle bracket.




Upper link frame bracket.






Crossmember with lower link brackets.

 

[Stoffregen Motorsports]

Frame plating had to be done before the brackets could be welded to the outside of the frame. I do mine a bit different. They are all custom and incorporate a steering box mount into them. The stock steering box location was perfect but since this was originally a right hand drive vehicle, I needed to put some sleeves in to hold the box tight.

 

[Stoffregen Motorsports]

Before I get too far ahead of myself, let's have a rundown of the parts we used.

The brackets are either custom made by me or modified generic from Ruffstuff or other suppliers.

The Hellfire knuckles use a custom steering arm setup to allow the use of high steer. Since we were not using leaf springs, the steering links could be mounted under the arms to allow for frame clearance. But the Diamond axle housing built for a LC diff did not allow the tie rod to be mounted in the rear hole of the arms, so we moved it to the front. This meant that the original driver side steering arm supplied by Hellfire was too short. I ordered up a new "right hand drive" driver's side steering arm that has two holes in it, problem solved.



The "one ton" steering joints are from Parts Mike and are of the intersect style so we could keep the bumpsteer to a minimum.

A flat pitman arm fit perfectly, but had to be reamed to fit the one tone joint. As a matter of fact, I had to machine new bushings for the steering arms too. I will eventually fill the old tie rod hole with a solid piece to keep them strong (I have heard of other people bending the arms there using the forward hole). The arms were preheated and the bushings were TIG welded into the arms and then post heated to keep the weld from cracking as it cooled. I use a small toaster oven for this.

This truck should have near perfect bumpsteer geometry.

 

[Taylor1]

Nice work so far. Will you enlighten us with details how you secure the three bolts and sleeve to frame on that flush tcase crossmember. I'm guessing the tcase crossmember frame sleeves are similar to the steering box frame sleeves pictured later.

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[Stoffregen Motorsports]

Thanks.

The sleeves were 7/8 x .120 tubing, welded at both ends, through the frame. There are captive nuts welded to the inside of the crossmember. With anti seize, the bolts can be torqued to over 200 lb/ft. Three per side is overkill.

There are also two 8mm bolts that help hold the crossmember in place while installing it. Once the six large bolts are installed and torqued, the two 8mm bolts (one on each frame rail) can be removed.

 

[Taylor1]

Thanks.

The sleeves were 7/8 x .120 tubing, welded at both ends, through the frame. There are captive nuts welded to the inside of the crossmember. With anti seize, the bolts can be torqued to over 200 lb/ft. Three per side is overkill.

There are also two 8mm bolts that help hold the crossmember in place while installing it. Once the six large bolts are installed and torqued, the two 8mm bolts (one on each frame rail) can be removed.

Gotcha. Bomb proof for sure. No room for error during assembly. Do you measure 5x before drill cross member holes and clamp it all down... something to keep captured nuts all aligned before/ during welding.

Curious because my last two cross member and skid efforts needed final tweaks to align after less than precise setup...

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[Stoffregen Motorsports]

In this case, I used the sleeved holes as pilot holes and then transfer punched the crossmember nut plates. I have learned over the years to be careful of shrinkage when welding, so I put a lot of thought into a welding sequence before I start laying down a bead.

Nothing sucks more than having a proper fit before weld and then completely distorted fit after.

 

[Taylor1]

Okay. Yes.

Keep it up. Always fun to watch your builds come together.

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[cruiseroutfit]

Loving it!

 

[Humvette]

I love your work

 

[Stoffregen Motorsports]

Thanks everyone.

I'm compiling more pics now so expect an update soon.

 

[tienckb]

Superb engineering and fabrication knowledge.


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