Interference: brake booster and CPP crossmember, please help!

[Jemo]

I have a CPP booster/MC and their tranny crossmember. The brackets on the booster/MC badly interfere with the crossmember. The booster combo has the standard bracket that mounts in the stock frame location which works fine. It also has a bracket pointing forward (it's the bracket pointing diagonally from top right to bottom left) that will work fine but the two rear facing brackets hit the crossmember and I'm not sure what to do. This pic is a top view of the booster.



Do you think it will be stable enough to just cut those rear facing brackets off? I kinda think not because most of the weight is at the rear. Just need some ideas because I'm stumped.

Thanks,
Jeff

[lonelywanderer]

i have the same power brake set up and was gonna make my own cross member. the local shop i ordered it from did a install on a 58 with the cpp crossmember and they said they had to modify it to work. it looks like a universal unit thats why i decided to make my own

[BigJock]

This seems to be a common problem, I made my own crossmember and 'offset' the left hand side to clear the booster on my AD.
I used a Master Power Brakes set-up and had the same clearance issues.
I haven't 'sussed' out the picture posting or else i'd show you.
I'm a newbie here too......

[entourageguy]

well start sussin' we like pictures ....

[BigJock]

entourageguy,I haven't worked out the individual pictures but here's a link to the whole lot.
http://www.flickr.com/photos/2601498...7606265799089/

Jeff(Jemo), there's pics of the gearbox crossmember in there somewhere!

[Jemo]

Thanks BJ. I did find the pic in your album but don't know how to save it and repost it. I'll post the link I show: http://www.flickr.com/photos/2601498...06265799089/#/

My situation seems to be quite challenging. My booster itself is right in front of the bracket for the crossmember. I'm starting to think about maybe cutting off the end of the crossmember and welding two arms that fork off the main crossmember at 45 degrees so it's a Y-shape on the driver's side. Hard to describe but I don't know how else to get around this.

Jeff

[BigJock]

Jemo, I don't see a problem with what you're considering,just make sure it's braced well and your welds are good.

It's all just part of the fun(?) these old trucks provide!
Nothing's ever straightforward!

[hsdropout]

I believe the tranny mount bolts to bottom of frame and tube hangs below the frame. I thought I would have the same problem but when I fit up motor & tranny, the mount needs to be low to get the correct angle for the drive line. And, if it's on the bottom you can shim it down if you need more angle.
Engine and tranny are angled about 3 degrees down in rear and differential angles up about the same 3 degrees..........U-joints need this to work properly.
I think there is info for this if you google stovebolt........
You probably ought to fit up before you take my word for it.....

[Tchia65]

Originally Posted by hsdropout

I believe the tranny mount bolts to bottom of frame and tube hangs below the frame. I thought I would have the same problem but when I fit up motor & tranny, the mount needs to be low to get the correct angle for the drive line. And, if it's on the bottom you can shim it down if you need more angle.
Engine and tranny are angled about 3 degrees down in rear and differential angles up about the same 3 degrees..........U-joints need this to work properly.
I think there is info for this if you google stovebolt........
You probably ought to fit up before you take my word for it.....

The normal tail shaft down is 3 degrees, but in order for the "U" joints to rotate their bearings there needs to be a 1 deree split. So if the drivetrain in 3 degrees down, then the pinon need to be 2 degrees up.

I have the no limit booster and bracket and had the exact same problem with the cross member wanting to be in the same spot as the booster. I had to cut the mount off the cross member, move the brackets back. Rotate the cross member toward the tranny and reweld the tongue back on the cross member. I had to set the drive train level anyway so this let me get the drive train to 3 degrees down. If you go this route make sure the truck is level. I attached a pic of the modified cross member.

[OrrieG]

Reference point for leveling the engine and trans is the carb flange or similar point of FI engines. In most cases it is parallel to the frame rails. From these posts it sounds like it is best to just build a mount from scratch. I did not have that issue because the 4wd mount is 4" lower than 2wd. My interference was with the brake lines and transfer case.

[Russell Ashley]

"The normal tail shaft down is 3 degrees, but in order for the "U" joints to rotate their bearings there needs to be a 1 deree split. So if the drivetrain in 3 degrees down, then the pinon need to be 2 degrees up."

That isn't exactly correct. Ideally the pinion angle and the tail shaft angle should be the same, as shown in Hsdropout's post. What's important is that the tailshaft, driveshaft, and pinion don't form a straight line.

[Tchia65]

[QUOTE=That isn't exactly correct. Ideally the pinion angle and the tail shaft angle should be the same, as shown in Hsdropout's post. What's important is that the tailshaft, driveshaft, and pinion don't form a straight line.[/QUOTE]

Then what is exactly correct?

[Russell Ashley]

Originally Posted by Tchia65

Then what is exactly correct?

You don't want one degree difference in the pinion angle and tailshaft angle. Ideally you want them to be the same, as the picture in the post I referenced shows.

[MrDude_1]

Originally Posted by Russell Ashley

You don't want one degree difference in the pinion angle and tailshaft angle. Ideally you want them to be the same, as the picture in the post I referenced shows.

yup.
by having them both at the same angle, they naturally cancel out vibration from each other.

as far as having them moving so they stay lubricated, as long as theres an angle on them, they're fine. its when they're almost perfectly straight that they dont rotate the needle bearings inside them... but you wont have that in our trucks unless you do an IRS and dont offset anything.

[Jemo]

Thanks all for the help.

I don't think any company's crossmember or booster would necessarily be better than the other because the motor mounts are where they are and need to be so the transmission mount is going to be where it is based on engine location. I looked at the No Limit part and it doesn't look much different from what I have.

Regardless, the mounting point for the transmission is exactly where the booster mounts to the frame. I had to cut one ear off the booster bracket so now the booster mounts nicely to the frame but there is no room for the crossmember so I'm going to have to work something out.

I don't think I can lower the crossmember like the pic above because the motor mounts are already at the height they're at and I don't want to cut those out and do it over again. If I just lower the crossmember mount, it's going to create a steep pinion angle I'd think. I'll see if maybe I can notch the crossmember and maybe weld on some gussets to make it work. I'll post pics with whatever solution I figure out.

Jeff

[Tchia65]

Originally Posted by Russell Ashley

You don't want one degree difference in the pinion angle and tailshaft angle. Ideally you want them to be the same, as the picture in the post I referenced shows.

Actually the 1 degree difference accounts for the tendency of the pinon to raise during acceleration. Especially with leaf spring rear suspensions. I have set up numerous chassis, and have never had vibrations, or fatigued u joints. So you stick with your picture I'll stick with what works.

[Russell Ashley]

Originally Posted by Tchia65

Actually the 1 degree difference accounts for the tendency of the pinon to raise during acceleration. Especially with leaf spring rear suspensions. I have set up numerous chassis, and have never had vibrations, or fatigued u joints. So you stick with your picture I'll stick with what works.

I've been following your build thread and obviously you know a thing or two about building a chassis that works, but you are wrong in this case. It's true that that pinion angle changes slightly on acceleration, but it changes slightly in the other direction when braking. If starting and stopping make up 10-20% of driving time, the u-joint angle is out of phase for all of the rest of the time that you are not accelerating if it isn't set the same initially.
Actually, this is probably a moot discussion, as one degree difference probably isn't going to be noticeable anyway.
We aren't going to agree on this so you continue to do what works for you and I'll do what works for me, which is setting the angles the same.

[whid]

I've got a MP Brakes power set up and a Chassis Engineering trans mount....my interference came with the master cyclinder hitting the mount...I took care of it by notching the mount and flipping the combination valve from the left to the right side...I did have to rework one of the prebent lines for the valve thou.....As far as pinion angle what I did was to zero out the carb base which took a 1" spacer under the tranny mount(which aslo gave me some much needed firewall/distributor clearance) then i put a angle finder on the bottom of the motor block where the starter bolts on..... mine showed -3deg....then a angle finder on the yoke on the rear end and raised it up until it read +3 deg...then welded it up.............whid

[hsdropout]

photo of my fit up.....tranny mount should clear below power brake master....
now that I have everything clean & painted, I'm going to fit everything up again.............crusty under there wasn't it........

[robnolimit]

No Limit to the rescue. As we were the first to build bolt in power brake kits, We also make the correct trans crossmember. Part #M-160, sells for $63.00. There is a benefit to building trucks in our shop, as we know what fits, and what doesn't.

[lonelywanderer]

Originally Posted by robnolimit

No Limit to the rescue. As we were the first to build bolt in power brake kits, We also make the correct trans crossmember. Part #M-160, sells for $63.00. There is a benefit to building trucks in our shop, as we know what fits, and what doesn't.

if i knew this i would have bought the power brake set up from you guys. on a side note you think your guys crossmember will work with the cpp power brake set up?

[hsdropout]

Got me curious so I checked again. Looks like I've got over an inch clear.
From what I have seen advertised, the crossmembers are very similar from one manufacturer to another, so it should work.

[BigJock]

Seeing as this thread seems to have 'morphed' into a pinion angle discussion, I agree with Tchia and Russel Ashley.

Bottom line is, get it wrong and you'll soon find out......excess vibration and/or early UJ failure.
I learned the hard way a few years back, the vibration was horrendous!

[MrDude_1]

U joint angle and static pinon angle are two separate but related topics.

U joint angle MUST be identical at both ends to naturally cancel harmonic vibration.

HOWEVER....

the static pinion angle must be angled downward so that under load, with the spring wrapped (or bushings compressed, etc) the pinion maintains a flat or downward angle.
having the pinion rotate upward eventually flips the u-joint angle to the point where they will have intense vibration, and are both overstressed.

as to what its set to initially, that depends on the vehicle. on my torque arm suspension drag cars, i usually end up with -3* down, because with torque arm, LCAs and poly bushings compressed, under a full drag launch, its perfect.
yet with other vehicles, they like more or less... go too far either way, and theres vibration.. if you have to go too far down to make up for launching, then you need more pinion angle control (traction bars, or stiffer control arms/bushings)

really i dont think anyone is disagreeing, i just think you guys are talking about two different topics using the same terms.

[MrDude_1]

oh, and as for the original topic:

no one ever said the transmission crossmember has to go straight across the frame.
theres nothing wrong with making one that bends and attaches several inches back on one side then the other.. remember, the crossmember is not there to keep the engine from tipping side to side, its there to hold the tailshaft at a given height, and hold the engine/trans centerline to the truck.