C4 Dropmember and Trailing Arm Conversion Install

[SCOTI]

Originally Posted by glock35ipsc

Danny - I am planning on swapping my 85 to trailing arms also. I called a couple weeks ago, but don't remember who i talked to. I asked about buying just the 73 and up crossmember, but was told that only the 67-72 crossmember could be sold separately. True, or did I get bad info? I plan on fabbing my own crossmember, unless you guys would be willing to sell the 73 and up member as a separate item. Whatcha say?

Wild83C10 - Looks very nice! Could you post some info on the coil-over brackets on the rear end, link or part numbers please? Also, do you think a 67-72 crossmember could be modified to resolve the floor interference problems?

Prob could modify it like the guys that 'lay out'. They shave the portion of the stock c.member that extends beyond the frame rail on the bottom; this would require it to be done to the top.

[SCOTI]

I'm curious about one concern.... The 67-72's have the drive shaft loop extended higher (above the top plane of the frame rail) for clearance. The CPP 73-87 conversion piece has the c.member loop flipped & it's on the bottom. The top portion of the c.member does not extend beyond the frame rail.

I know on my 68 w/the stock TA c.member, the d.shaft was pretty close @ the top (~8" drop). My 74 has the top of the axle tube within 1" of the bottom plane of the frame rail so it looks to be several inches lower than Wild83C10's truck.

I'm wondering what kind of clearance there will be @ my ride height?
What ride height is the CPP 'kit' meant to be set at (2/4 drop; 4/6 drop, etc...)?

[68 TT]

Originally Posted by bluex

Would a stock 67-72 crossmember not work?

With a long bed the 67-72 crossmember might work. The crossmember stops just in front of the bed. It might tuck into the raised section of the cab right behind the seat.

[bluex]

Originally Posted by SCOTI

I'm wondering what kind of clearance there will be @ my ride height?
What ride height is the CPP 'kit' meant to be set at (2/4 drop; 4/6 drop, etc...)?

Originally Posted by bluex

From CPP about the kit:

Kit is designed for 63-72 arms and will work with a stock set of arms.
The truck in that video uses their modular brake kit with a 2" drop spindle
They also used a 2" drop spring up front for 4" total.
Their rear arms have no drop built into them
and the truck has 3" 63-72 drop coils in the rear, or can use any other drop or stock spring for those years.

Scoti, Here is the info I got from them when I called about the kit they installed on their '79. I dont think it is as low as yours.

I think you will use a shorter drop spring than your current drop amount since the arms go under the axle? (I have shackle/hangers now for a 4", but I might have to use a 2" spring to get the same ride height?) That is the only way that having a 4" drop up front and a 3" out back sounds right to me..

[72BlckButy]

Nice looking install!

[DKN]

Originally Posted by SCOTI

I'm curious about one concern.... The 67-72's have the drive shaft loop extended higher (above the top plane of the frame rail) for clearance. The CPP 73-87 conversion piece has the c.member loop flipped & it's on the bottom. The top portion of the c.member does not extend beyond the frame rail.

I know on my 68 w/the stock TA c.member, the d.shaft was pretty close @ the top (~8" drop). My 74 has the top of the axle tube within 1" of the bottom plane of the frame rail so it looks to be several inches lower than Wild83C10's truck.

I'm wondering what kind of clearance there will be @ my ride height?
What ride height is the CPP 'kit' meant to be set at (2/4 drop; 4/6 drop, etc...)?

When we made the conversion kit we had a short bed truck. The rear axle will bottom out into the C-notch at the same time the bed floor will bottom out into the differential. The crossmember mounts up high against the floor of the cab. The dive shaft loop hangs down off the bottom of the crossmember but is still higher than the bottom of the frame rails under the cab. The frame is not straight; it is very low under the cab, then rises up to the bottom of the bed. The reason the crossmember doesn’t work on a long bed is because the new location for the crossmember will be much higher, and will need to mount on a level section of frame instead of the section of frame that is angled from under the cab to the bottom of the bed. The cross member is shaped like a Z rather than a C. If we make a crossmember for the long bed I expect that it will have a larger lower loop for the drive shaft. The loop will still be higher than the cab section of frame. I expect that all of the other parts of the kit will be the same, only the crossmember is a problem for the long bed trucks.

Danny Nix
CPP

[SCOTI]

Originally Posted by DKN

When we made the conversion kit we had a short bed truck. The rear axle will bottom out into the C-notch at the same time the bed floor will bottom out into the differential. The crossmember mounts up high against the floor of the cab. The dive shaft loop hangs down off the bottom of the crossmember but is still higher than the bottom of the frame rails under the cab. The frame is not straight; it is very low under the cab, then rises up to the bottom of the bed.

The c-notch & bed floor bottom out @ the same time on my 74. Your description of the frame is just like the 67-72's (low under the cab & kicks up as it transitions to the bed). I'm going to crawl under my 74 today for some dimension verifications & will try to compare your description of the c.member mounting location while under there.

[Wild83C10]

Originally Posted by tomtuna1978

i like how you put the rear coil over outside the frame on that tube you put threw the frame ! what wall thickness is that tube ? and od ? thats what i wanted to do on my 4x4(shocks only) 79 c10.

The wall thickness looks like .120, the OD is 1-5/8.

[Wild83C10]

Originally Posted by glock35ipsc

Wild83C10 - Looks very nice! Could you post some info on the coil-over brackets on the rear end, link or part numbers please? Also, do you think a 67-72 crossmember could be modified to resolve the floor interference problems?

Rear suspension P/N:
lower brackets: C2047 (Competition Engineering)
Upper brackets: TB103GBK (QA1)
Crossmember: 7387TAC-LDL (CPP)
Adj track bar: 6572DTBK (CPP)
Coilovers: DR3855B (QA1)
Springs: 7-450 (QA1)

Just about anything is possible as long as you have the skills and time to modify the x-member I'm sure you can get it to work. My opinion is that the CPP x-member was worth it.

[SCOTI]

Originally Posted by bluex

Scoti, Here is the info I got from them when I called about the kit they installed on their '79. I dont think it is as low as yours.

I think you will use a shorter drop spring than your current drop amount since the arms go under the axle? (I have shackle/hangers now for a 4", but I might have to use a 2" spring to get the same ride height?) That is the only way that having a 4" drop up front and a 3" out back sounds right to me..

I would be by-passing the coils all together & moving directly to bags since I'm already using them in an air-over-leaf fashion (home-made) on my truck now.

Because my 74 has the HD rear set-up, that 8-leaf spring pack rides like a swb 3/4 ton on rough roads. I want them out of the way so I can run truck arms w/bags just like my 68 was set-up (ride quality was muuuuuuch better).

[Wild83C10]

Heres a picture of a 67-72 chevy truck frame. The light blue line is the x-member location. The red lines are the 73-87 frame profile. Obviously the lines aren't exact but just to give you an idea of how the frames are different.

[bluex]

Originally Posted by SCOTI

I would be by-passing the coils all together & moving directly to bags since I'm already using them in an air-over-leaf fashion (home-made) on my truck now.

Because my 74 has the HD rear set-up, that 8-leaf spring pack rides like a swb 3/4 ton on rough roads. I want them out of the way so I can run truck arms w/bags just like my 68 was set-up (ride quality was muuuuuuch better).

That is exactly why I want to do it as well. With the heavy half package on mine it rides like crap unloaded. Now put about a ton in the bed and it rides like a caddy....

I took it for a ride sunday and hit a dip in the road and almost hit my head on the roof when the rear went over it. It was never very smooth riding unloaded as a long bed, but when I converted it to short bed it got waaayyy worse..

[SCOTI]

Originally Posted by Wild83C10

Heres a picture of a 67-72 chevy truck frame. The light blue line is the x-member location. The red lines are the 73-87 frame profile. Obviously the lines aren't exact but just to give you an idea of how the frames are different.

Yeah, we looked under the frame & I could see where the 'initial' kick-up is vs how the 67-72 frame is (I have a 68 swb frame sitting on my trailer). The CPP dropped center is still higher than the bottom lower plane of the frame rail.

[aggie91]

I also looked at a LWB mid 80's truck. There is a kick up in the frame rail about 1/2 way between the front cab mount and the rear cab mount. after that it is straight until just past the front spring hanger where it kicks up again to go over the rearend housing.

Does the SWB frame have the same kick up under the cab? I do not have one handy for a visual inspection...

[JW76]

yes it does and the crossmember goes in where the kick up is on the shortbed. that is part of the issue why it wont work on the longbed because the longbed calls for a crossmember to be located on the straight part of the frame which is higher than in the kickup

[JW76]

in addition, when the arms are located that high up on the longbed (the pivot point).... due to the shape of the frame, when you swing the arms they want to hit the frame so you don't have much suspension travel. HRH is building me a crossmember that solves this problem for my longbed and pefects the geometry.

[aggie91]

I saw HRH install on a 3/4 ton on their site. I did not like how the crossmember was that much below the frame rail. But, it doesn't hang below the lowest part of the frame and is braced correctly, then it really does'nt matter...

I am lucky, mine is a '65 and I don't have to worry about it....I already have the trailing arms..

[JW76]

I talked to the Steve at HRH and he said that one is that low because of the ride height the guy desired. The one for my truck will be a little less low but still lower than just sticking a stock 67-72 between the rails. As I said it has to do with the arm clearance and Steve says it has to do with the geometry

[aggie91]

Any progress on this truck?

[love my 72]

Wow! great work! im loving that coil over set up! when i buy my C4 DM i want coil over set up! and that anti-sway bar is just awsome! i always wondered what the DM would use for an anti-sway bar!

Keep up the good work! but keep us posted too!!!

[Wild83C10]

Originally Posted by aggie91

Any progress on this truck?

I have all the suspension together and I drove it some this summer/fall. Doing some additional work this winter.

I'm bad with pictures, but I will post some up. Can't see much of the suspension work behind the turbo stuff though.

[Wild83C10]

Ok here's some completed for now suspension pictures. Next upgrades: larger front swaybar, rear sway bar, frame stiffening and then a roll cage.

[SCOTI]

Man.... That's quite the package of parts you have pieced together. I imagine you have an ear to ear grin when you're behind the wheel.

[Wild83C10]

Yes I do. I waited all this time for the suspension upgrades but the turbo seems to give me the biggest grin. I really haven't spent the time tuning the suspension yet though.

[aggie91]

that looks great! I bet that turbo motor is just to much fun.

How much travel does the rear suspension have? It looks like only a couple of inches of compression.
Posted via Mobile Device