OK...Got a crazy idea here and need some opinions if this will work. Been thinking of how to raise the rear of my 76 up without compromising the half shafts too badly. After I put the fender flares and the wide meats on I thought I had enough clearance....until I moved the car and the rear settled down, then I had about 1/2 inch between the flare and the tire. Put some air shocks on it and ran them up....now I have about 1 1/2 inches but I am still not comfortable....I can drive it but one big pothole may spell disaster for the flares. I can not raise it anymore due to the shock travel maxing out and also must consider the angle of the half shafts. If I custom make a shock extender block for the top I would be able to increase the travel of my shock but at the cost of the half shaft angle....I need another 1/2-3/4 inch.
Now....this winter I have to drop the rear diff anyway due to a leaky seal and was just planning to replace it with a new diff with 3.70 gears. What if when I did so I custom made a 1" to 1 1/2" spacer that would go between the rear cross member and the differential? I mean one of substantial size to space the entire joining area, drilling the 4 bolt holes threw it and using longer bolts to secure the cross member to the differential???? Would this then not lift the body while keeping the half shafts close to stock angle???? Will this work??? I will still have to custom make the shock extender but then these would not bear all the burden of the lift......Or have I just been sniffin too much WD40?

 

I'll let some of the suspension guys comment but I'd have to question the use of the current rear wheels. Not sure how much you are throwing the geometry off by lowing the pumpkin.

Could you mill the wheel hubs to move the wheels in a little to clear or user a narrower tire?

 

Rookie here......the steering might get "squirrelly" if you add a spacer that thick to raise the body for tire clearance/you could try it though.

You would need to weld tapered shims to the add-on block to correct the angle of the pinion/differential so you don't beak the u-joints! Jegs or Summit might sell the tapered shims.

 

What size bolts are you using? 6 inch bolts and a 9 leaf spring will set it pretty high.

 

I replied to your other post.

Your idea of making a thick plate to go between the differential and frame will not work....because if you ONLY putting it between the carrier and the cross member...you are putting your differential at an incorrect angle...and spacing the front mount area of the differential...you will cause the drive shaft to come in contact with the frame...or very close to it.

DUB

 

Am working all w/e but will have to crawl under the car to take a gander on Monday but I am confused. If say I put a 1inch spacer between the top of the diff. Unit and the cross member, should it not lift the body while keeping the drive train in line? How does a flat plate change the angle of the diff. If it lifts the rear body only how does this bring the drive shaft closer to it? Maybe I am missing something here but it makes no sense in looking at frame drawings. The shock extention mounts I can weld solid if need be. Not trying to argue just to understand.

 

The diff. unit also has a forward mount that attaches to the frame. Lowering just the rear of it will put it at a huge angle. If you also make a block to lower the front diff mount, the driveshaft will hit the frame unless you modify that crossmember too (i.e. cutting material away for clearance).

 

The other members must be talking about the crossmember that is midway between the transmission crossmember and the "nose" of the differential.

 

Ok....now I understand....I will look at it....thank you!!!!

 

What size tire and wheel ?

 

I got 29-15.5-15s....got a lot of money in those tires and don't want to change them out...know others that are running 31s. Problem is that when I faricated the wheel flare I did not move the car and let it settle back down after jacking the back end up....thus I thought I had more clearance than I do. Clearly my fault and a problem now but not one that I will not overcome. Having the flares any higher on the fender would have looked odd and I will just have to use some ingenuity to overcome this, even if it means having a cross member custom made along with other frame parts

 

NOW we are getting into Rocket Science! How much GAP is there between the tire and the frame? If there is an inch or more...... You could buy shorter half shafts....then offset the front section of the trailing arms that fit in the pockets....shorten the strut rods or buy adjustable strut rods in order to "move" the wheels closer to the frame (that seems like the least expensive route). You could actually make all these changes along with the "tapered" diff. spacer yourself eliminating labor cost.

 

A lot to digest in this thread....I will look but don't think I have a lot of room....I had already cut off and remounted the parking brake bracket to the top of the arm to give clearance for the tire. I will eye out and post more for input. ..everyone's suggestions and opinions are greatly appreciated. .this has got to be resolved one way or the other.

 

It's a lot to consider......but I'm referring to the gap between the tire and the frame-----not the tire and the trailing arm, since you've already reduced that gap as much as possible. If there stikk is a gap there, relocating the entire trailing arm assembly closer to the frame is what I am suggesting/along with adding the diff. spacer.

 

Knowing that you are not going to change out tires.....and re-working the body is OUT OF THE QUESTION...obviously.

"Doorgunner' has a very good idea of moving the trailing arm and shorten components inwards...IF you can do it.

AS I mentioned in the other post....your steel leaf spring can be the culprit. And it can be replaced with another steel spring....or contact Vette Brakes and Products and see about getting a seriously high rated fiberglass spring.

Also...if custom modifications are going to be made and you really want an 'insurance policy' that can guarantee you that there is NO WAY for the tire to contact your quarter panel. You will have to make a suspension travel stop....so the trailing arm can only go to a point an make contact with it. And this would require serious 'beefing-up' of the trailing arm and making a rubber stop or whatever you choose to go into the rubber stop mount area currently and extend it downwards.

DUB

 

I would disconnect the rear spring and raise and lower the rear suspension through its full travel to actually see if and where its going to rub before doing any more mods. You may be trying to fix something that isn't broken.

 

Agree...

Also agree with DUB on the bump stop.

With a couple of jacks and with the tires on the ground with a jack under the third member use the second jack to remove spring tension and remove both suspending bolts. Measure the gap at the bump stop at ride higth then lower the car as low as possible without the tires touching the flares. Check the bump stop gap again. This will give you the amount you need to space the rubber bump stop to prevent the suspension to travel any lower than space available between flare and tire. This will allow you to set ride hight with no further concern of the tires hitting body work. The difference in bottom gap and upper gap will give you the rate of travel. Shocks should be well within.

 

Now that sounds like the solution I have been looking for....I will do this.

 

Keep us posted/pics if possible for other members who need the info.

 

Keep in mind that even though this is just a suggestion that seems to be a good one. PLEASE stop and consider many forces in play when you plan on employing this idea. Which is why I wrote that (I feel) that the trailing arm would need to be drastically strengthened if it is now being used as a suspension stop point. So...that flat piece of steel on the top of the trailing arm I have seen be bent MANY TIMES....so make sure you take this variable into consideration when fabrication up your 'stop'

BECAUSE with this area being a stop...you have to consider if the force being applied on the trailing arm...would it effect the condition of the trailing arm bushing...or 'possibly'...cause the trailing arm to loose its camber adjustment.

F=ma (Force is equal to MASS times ACCELERATION)

DUB