Adjustable Anti Squat brackets for rear trailing arms... Question?

[Slik66]

I have a POL Drop crossmember with Anti Squat brackets... The Anti Squat brackets have 5 holes for mounting the trailing arms (stock to 4*).

Is there a way to get these mounted "close" to the right position by calculating suspension drop?

A local guy from a body shop said the trailing arms need to be level to just slightly down at the rear end>?!?

[Rich 5150 69]

Too many variables...ride height, tire height, weight, stickie tires for the launch, how much flex you have in the trailing arms ( reinforcement plates ), overall rake of truck, spring rate, assemble it all, use the lowest hole first and see where the pinion position is, one to two degrees down at the pinion...you still may have to shim the housing on the trailing arms to optimize the setup. Use a go pro camera on a mount under the truck aimed at the pinion to get the results on a hard launch.

[Slik66]

Originally Posted by Rich 5150 69

Too many variables...ride height, tire height, weight, stickie tires for the launch, how much flex you have in the trailing arms ( reinforcement plates ), overall rake of truck, spring rate, assemble it all, use the lowest hole first and see where the pinion position is, one to two degrees down at the pinion...you still may have to shim the housing on the trailing arms to optimize the setup. Use a go pro camera on a mount under the truck aimed at the pinion to get the results on a hard launch.

Not setting it up for racing, just street cruiser.
No matter what hole I mount the trailing arms, the pinion does not point down at all.

[Rich 5150 69]

The lower you go the higher the pinion will ride up, you`ll need to start shiming it under the axle/trailing arms. this angle will be one to two degrees down from the transmission plane...long or short bed...? Two piece drive shaft..?

[Slik66]

Short bed.
Right now I have 6" lower springs in rear.
I don't have a driveshaft yet but plan on a one piece Aluminum.

I will definitely need an angle shim under the axle it seems

[Slik66]

Hard to see, but if I draw a straight line from the axle to the tranny, it will be just above the tail shaft of trans.

[Rich 5150 69]

Bubble protractor place on end of trans housing, note degrees, place on pinion flange, note degrees, needs to one to two degrees down from trans position..
https://www.lowes.com/pd/IRWIN-Magne...yABEgLzwvD_BwE

[Slik66]

Originally Posted by Rich 5150 69

Bubble protractor place on end of trans housing, note degrees, place on pinion flange, note degrees, needs to one to two degrees down from trans position..
https://www.lowes.com/pd/IRWIN-Magne...yABEgLzwvD_BwE

Now that's service!!! Thanks for the link!

[1Ratty64]

Thought i would throw in my .02........you want to set up your trailing arms to intersect on or slightly above your anti-squat line. You don't want to go adjusting your trailing arms for pinion angle.....you do that with pinion angle shims after you properly set the instant center. Even though you said you're not going to be racing, you look like you are doing things right so far so i just figured i would help out a little.....and besides, why give up traction and good handling characteristics if you don't have too.

[Slik66]

Yeah, I've been searching Driveline Alignment and have got a better understanding of what I need to do.

The only thing I haven't found an answer to yet..... is there a proper way to adjust the engine/trans combo?
My transmission hits my crossmember so I will need to shim the trans mount up about 1/2". When I do that it will change the angle of the crankshaft slightly so I'm trying to search the proper way to align that Before I align the pinion/shaft/trans

[Slik66]

I do remember reading something about the Intake plane being level or something?

[Slik66]

Also.... another reason why I'm wondering if I need to do something with the engine/trans angle is that the crossmember mount and the trans mount angles are pretty far off. Yes, I can crank a bolt down and it would work, but doesn't seem right to me.

[1Ratty64]

Engine inclination angle is only relative to pinion angle, most carb intake manifolds have roughly 6 degrees built in to the carb flange so the carb sits level......but that only takes into account engine angle, not suspension and tire rake. Theoretically you want a carb to sit completely level, but the real world isn't theoretical......thus why we have float adjustments. Basically you don't want your engine inclination angle too extreme because you are going to have to match the inverse of that angle at your pinion. 6-8 degrees of engine angle is what you will typically find from the OEM, but if you ever look at some of the old gassers of the 60's....you will see some extreme crankshaft center line angle because they were going for maximum weight transfer. As long as you keep the angle as low as possible you will be fine.

[1Ratty64]

I will add that since it appears you are working with a fairly bare chassis, that you either need to wait until you have your body mounted or simulate curb weight/finished ride height before you permanently set any angles. I use to only tack in engine/trans/link mounts until i had the body back on and close to fully assembled weight before finalizing my engine position and suspension geometry.

[Slik66]

Thanks for taking the time to type all That!

I will set the pinion angle once the truck is back together. My original reason for the thread was to figure out a rough starting point to mount my trailing arms, which I think I figured that one out. Once I drive the truck that might change

Thanks again

[1Ratty64]

No problem man, if you need any future help just hit me up

[Captainfab]

The trans mount, mounting surface of a trans crossmember is supposed to be at an angle, not flat. The factory trans crossmembers have that slight angle to the mount surface.

Originally Posted by Slik66

Also.... another reason why I'm wondering if I need to do something with the engine/trans angle is that the crossmember mount and the trans mount angles are pretty far off. Yes, I can crank a bolt down and it would work, but doesn't seem right to me.

[Slik66]

Originally Posted by Captainfab

The trans mount, mounting surface of a trans crossmember is supposed to be at an angle, not flat. The factory trans crossmembers have that slight angle to the mount surface.

So do I need to modify the crossmember to match the tranny so there's no stress in the mount, or let it fly?

[PGSigns]

I always bolt the tranny to the crossmember first then drill the frame holes. That way they end up in the correct place. I would remove the bolts at the frame and pull it up tight to the trans and see what needs to be done to the cross member at the frame end. I am also one who likes to set the engine angle with the cab on.
Jimmy

[Slik66]

Crossmember was a tight squeeze in the frame rails so there's no give on either side.
I think I'm going to cut the mount area off the crossmember and move it up, since I need to get the tranny up off the crossmember anyway. Got a buddy that owns a powder coat shop so I can get it re powder coated after I do that for nothing.

[Slik66]

So, since this is my first full build frame off thing.... my thought was to center the transmission in between the frame rails. Is this not correct?

I can modify the trans tunnel if needed, but wanted to keep a straight line to the axle?!?!

[PGSigns]

Doing it with the cab on will let you see a couple of things on is the angle because if it is low in the back the HEI will hit. I just took a second look at your cross member in the pictures and it looks like it is upside down. All the ones I have used or built that mount faced the other way. This may solve a lot of issues bot now and in the future. I would pull it and flip it over and see how it looks. I think you will find it fits fine.
Jimmy

[Slik66]

This is the way it's made to go from the MFR... I took another pic. There's no way I can flip it around because the crossmember will be hitting the pan, if I'm understanding you correctly.

It's made to let my exhaust tuck up above the crossmember...

[Slik66]

I just called Western Chassis... Crossmember is in correctly.

They couldn't tell me why the transmission is hitting though.
Easy fix