Rear Drop.....Adjustable trac bar?

[Leverhead]

Just finished a 3" front drop (cpp 2" modular/1" springs) and moving on to 4" drop in back (4" springs, shock relocators, trac bar?). For those who have done the same, can you remember how much difference there was from the original trac bar length before your drop, to the 'after' drop length. Looking at CPP adj trac bars (the std length ones that install in the factory holes/brackets) ...they have 2....one is 27" long (63,64) ,& the other is 24"(65-72). The OEM one in my truck now ('64) is 23 1/4"...it looks like it was cut and re-welded. Also, how was the angle of your trac bar after you installed it on your dropped truck? Any problems with the ride afterwards? Trying to get this right the first time. Thanks.

[frankslagoon]

I dropped my 63 4 inchs and didn't do anything with the panhead bar. later I went to a 66 rear end and had to mod then the rear end seemed pretty centered after the drop

[Leverhead]

I'm assuming you modified the OEM trac bar? Cut and weld type thing? I read that Ide be better off with the 'long' adj trac bar that mounts to the opposite side trailing arm (CPP 6372DTBK) but I think it might be overkill for a 4" drop. I'm currently of the mindset that the std adj CPP (6364DATB, 6572DATB) would suffice but still not 100% sure.

[frankslagoon]

Well I didn't do anything when I first dropped it 4 inchs . I used jeep TJ springs and a shorter set of shocks.

[Leverhead]

I meant with the 66 rear...you said to had to mod. Did you modify the oem bar or use and adjustable?

[chevyrestoguy]

If you use the OEM bar with a lowered suspension, the rear end kicks over to the driver's side, and gets worse when the suspension is compressed. On any drop lower than 4", you should also change out the track bar to an aftermarket bar that ties the driver's side framerail to the passenger side trailing arm. I used one from Early Classic, and it's a really nice piece. You should also relocate the shocks as well to get the angles corrected. In the stock position, the lower you drop it puts the shocks at a radical angle and they begin to lose their effectiveness. Early Classic addresses both of these issues in their Super Track Bar kit.

[frankslagoon]

I just measured and rewelded . I'm not sure why everyone buys the aftermarket panhead bars. When I first put the 66 rearend in I just bent the bar to fit so I could do a test drive. That even worked ?

[frankslagoon]

Originally Posted by chevyrestoguy

If you use the OEM bar with a lowered suspension, the rear end kicks over to the driver's side, and gets worse when the suspension is compressed. On any drop lower than 4", you should also change out the track bar to an aftermarket bar that ties the driver's side framerail to the passenger side trailing arm. I used one from Early Classic, and it's a really nice piece. You should also relocate the shocks as well to get the angles corrected. In the stock position, the lower you drop it puts the shocks at a radical angle and they begin to lose their effectiveness. Early Classic addresses both of these issues in their Super Track Bar kit.

Well over 4" is a whole new ball game . But he's talkin about 4 "

[Leverhead]

OK I see. The bar in the truck now was cut and welded also...maybe because I have a 65 rear in a 64 truck (diff post vs axle bracket). The 4 inch rear drop gets blurry when it comes to the oem style trac bar vs the 'long' style (that mounts to the pass side trail arm).....hence my confusion about what 'style' of bar to use. I've heard the argument for both. But I thought lowering would push the rear axle over to the pass side necessitating a shorter bar to pull it back over to the driver side again to center it..which is opposite of what chevyrestoguy is saying.

[frankslagoon]

Originally Posted by Leverhead

OK I see. The bar in the truck now was cut and welded also...maybe because I have a 65 rear in a 64 truck (diff post vs axle bracket). The 4 inch rear drop gets blurry when it comes to the oem style trac bar vs the 'long' style (that mounts to the pass side trail arm).....hence my confusion about what 'style' of bar to use. I've heard the argument for both. But I thought lowering would push the rear axle over to the pass side necessitating a shorter bar to pull it back over to the driver side again to center it..which is opposite of what chevyrestoguy is saying.

My swap was the same as your 64 to 65. I just went from 63 to 66 but when I dropped the truck it still had the 63 rear end and original bar. you couldn't tell any difference by lookin and the wheels seemed centered. I know I measured but can't remember, cause didn,t plan on leaven the 63 under there anyway. I just centered everything up with the 66 and made the panhead bar fit. you would have change length for sure just going from 64 to 65.

[Leverhead]

Thanks for the info. I think I'll go for the CPP 24" bar (6572DATB). Tech says the adj range is 22 5/8" (shortest len) to 24 1/2" (longest len) which I think will work fine. I may have to move the driver side frame mount a bit forward..not sure but we'll see.

[frankslagoon]

Originally Posted by Leverhead

Thanks for the info. I think I'll go for the CPP 24" bar (6572DATB). Tech says the adj range is 22 5/8" (shortest len) to 24 1/2" (longest len) which I think will work fine. I may have to move the driver side frame mount a bit forward..not sure but we'll see.

I just measured my bar it's touch over 23.5 inchs center hole to center hole so you should be good

[Leverhead]

Sounds about right. But I suspect I'll be needing a shorter bar than what I already have. Thanks.

[PGSigns]

When I did the 66 I wen to the early classics longer bar. The reason for the longer bar is the arc is longer so the side to side movement is less as the suspension travels. As you drop the truck it pushes the rear to the pass side till the bar get to a level point and back to the drivers sides as it goes past level. The longer the bar the less this happens.
Jimmy

[chevyrestoguy]

Originally Posted by Leverhead

.... But I thought lowering would push the rear axle over to the pass side necessitating a shorter bar to pull it back over to the driver side again to center it..which is opposite of what chevyrestoguy is saying.

You are correct, I got it backwards. Sorry.

[Leverhead]

Originally Posted by chevyrestoguy

You are correct, I got it backwards. Sorry.

No problem. Thanks for answering.... and you are correct that it would start to pull over to the drivers side as the bar travels past level. So like PGSigns says it would depend on how much drop and where the bar ends up.

I found this explanation which is really helpful.

http://talk.classicparts.com/showthread.php?t=14368/

According to the data a lowered street truck wouldn't have that much articulation that you really need the 'long' style bar....the difference between a long and short bar isn't that much to begin with. I think it depends on the angle of whatever bar at ride height anyways.
For certain the longer bar woudnt hurt anything....except the wallet.

[ol_skool_chevy]

I just cut and made my stock track bar longer to center the axle....works just fine

Im sure later i will get a adjustable one I want to change my tires to 275 70 15 and might need better adjustablity

[Leverhead]

Spoke to tech @ ECE and confirmed that for a 4" drop the 'long' style may actually be worse....so stock style bar it is. I noticed that the ends/bushings of the bar that is in there now are off due to the angle ('65 diff, '64 bracket/frame location). I'll have to move the '64 bracket rearwards a bit ('65 location) for my '65 diff to get the horizontal angle of the bar correct.

[62jimmy]

A bit off topic, but if you get a chance post up some pictures once you get it lowered, I've got a 62 I would like to lower with the same combo of parts...

[Leverhead]

No problem......will do. Just getting started now. Need to get some more parts ordered. Getting the trac bar bracket off the frame now so I can get it re-set at the correct angle.....those rivets back there are tough.

[Leverhead]

OK finally got this done (3/4 drop). Some pics as requested.

The 24" track bar worked out well (smallest 22 5/8, longest approx 24 1/2+ - this is with 1" of thread inside the tube at both ends) and is parallel with the ground at ride height. The mount had to be moved to get the angle correct (64truck/65 rear) and also clears the diff cover. Rivets were tough to remove in this corner, but the mount at the correct position clears the replacement bolts at the frame mbrs perfectly. The side bolt ear had to be sliced, bent in and rewelded to mate back up to the frame.

Springs dropped rear exacty 4".

Rear axle clearance = approx 3.5" from tube to frame-cut 1.5" off bumpers so clearance with bumper is 3". Diff to bed is 4".

I 'm happy with the ride and look, and comfortable with the remaining suspension travel.

Part#'s
Shocks KYB 344426
Rear track bar: CPP 6572DATB 24" adj
Shock relocators w hdw: CPP 6370SRK
Springs: CPP RCS603-4
Trail arm bushings: Energy 3.3123G
Rear sway bar: CPP7401
Grade 8 hardware for trailing arms pivots, spring mounts, rivot replacement, misc

Hope this helps.

[PGSigns]

Truck looks good.
Jimmy

[bj383ss]

Thanks so much for posting your results, pictures and part numbers. Saved all this for future reference. I had a hell of a time getting my trac bar back on and now I know why. I have a 70 rearend in my 64' So I need to move the bracket.

[Leverhead]

Thanks and your welcome. The only other issue is the front of the wheel well opening is closer to the tire (30x9.5x15 with 1.25" spacers) now and will rub on the bottom front edge on bumps. Going to roll the edge and do a little trimming for more clearance.

[nsb29]

watts link