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Username Post: Rear Axle Housing Travel        (Topic#353819)
SandDabMcSkeg 
Poster
Posts: 89

Loc: Coos Bay, Oregon
Reg: 01-04-18
11-08-18 04:50 PM - Post#2750813    

Anyone know how far rearward the rear axle housing travels as stock springs and shocks flex? On open driveline.



Edited by SandDabMcSkeg on 11-08-18 10:10 PM. Reason for edit: No reason given.

 

Chevs of the 40s

Shepherd 
Frequent Contributor
Posts: 1505

Loc: Lake George, NY
Reg: 11-11-15
11-08-18 06:33 PM - Post#2750830    
    In response to SandDabMcSkeg

Stock torque tube driveline?



 
SandDabMcSkeg 
Poster
Posts: 89

Loc: Coos Bay, Oregon
Reg: 01-04-18
11-08-18 10:09 PM - Post#2750846    
    In response to Shepherd

Should have specified, on open driveline.




Edited by SandDabMcSkeg on 11-08-18 10:10 PM. Reason for edit: No reason given.

 
40grit 
Contributor
Posts: 397
40grit
Age: 73
Loc: Chattanooga, Tn
Reg: 07-08-13
11-09-18 02:47 AM - Post#2750856    
    In response to SandDabMcSkeg

Normal rule of thumb is to leave at least 3/4" for travel in the slip yoke at the transmission if that helps any.

John

Just Slightly Abrasive


 
tommy49 
"4th Year" Silver Supporting Member
Posts: 2439
tommy49
Loc: Kaleva, Michigan
Reg: 09-28-12
11-09-18 08:18 AM - Post#2750877    
    In response to SandDabMcSkeg

I don't think there would be any significant rearward "swing" movement at all. The forward spring bolt is the pivot point. Remove the shocks, hang a plumb-bob from the housing and mark the floor. Jack the rear axle all the way up and mark the floor again. That will tell you what the rearward travel is. The total angle travel probably isn't more than 12 degrees. I went through something this when I put in new bump stops.

Tommy

49 Deluxe Sport Coupe, 55 235, 700r4, Blazer rear axle, 4 wheel power disc brakes.

https://www.flickr.com/photos/tommyfortynine /album...



 
40grit 
Contributor
Posts: 397
40grit
Age: 73
Loc: Chattanooga, Tn
Reg: 07-08-13
11-09-18 08:36 AM - Post#2750879    
    In response to tommy49

  • tommy49 Said:
I don't think there would be any significant rearward "swing" movement at all. The forward spring bolt is the pivot point. Remove the shocks, hang a plumb-bob from the housing and mark the floor. Jack the rear axle all the way up and mark the floor again. That will tell you what the rearward travel is. The total angle travel probably isn't more than 12 degrees. I went through something this when I put in new bump stops.



Until I read Tommy's post, I didn't realize I misread the origional post. I agree. The rearward movement is margional but as the leaf spring straightens out there will be a limited amount.

His suggestion to mark the floor with the weight both on and off the spring should answer the question.

I apologize for answering a question that was not asked.

John

Just Slightly Abrasive


 
SandDabMcSkeg 
Poster
Posts: 89

Loc: Coos Bay, Oregon
Reg: 01-04-18
11-09-18 08:54 AM - Post#2750883    
    In response to 40grit

I am concerned about clearance between a new gas tank and the differential, (station wagon) we are using one from a 55-56 wagon because they are bigger capacity, the 51 is only 12 gallons.



 
DanD1950 
"3rd Year" Silver Supporting Member
Posts: 873
DanD1950
Loc: London Ont. Canada
Reg: 10-16-11
11-09-18 02:42 PM - Post#2750913    
    In response to SandDabMcSkeg

If you have at least a 1/2 inch clearance with the car sitting static; the diff should never hit the fuel tank. If it does, check the front bushings of the leaf springs. Spring wrap will allow the dif to rotate; but it will not allow rearward movement.

Dan.

50 Styleline Deluxe, 2 Door Sedan, Was a 216cu", Three Speed Manual. She now has a 4.8Lt V8 LR4 injected engine, 4L60E 4 speed automatic, 10 bolt diff 342 gear with an Eaton C80 Locker



 
Mike JW 
"6th Year" Gold Supporting Member
Posts: 1334
Mike JW
Loc: Arroyo Grande, CA
Reg: 01-19-06
11-09-18 07:06 PM - Post#2750941    
    In response to DanD1950

If your going with stock springs,and a V8 motor you may want to put some different springs in the rear. The stock springs were designed to be used with the torque tube. Without the torque tube you'll get a lot of spring wrap.



 
SandDabMcSkeg 
Poster
Posts: 89

Loc: Coos Bay, Oregon
Reg: 01-04-18
11-12-18 03:22 PM - Post#2751186    
    In response to Mike JW

What exactly is spring wrap? And if I replaced the springs, what is a good replacement?




 
Shepherd 
Frequent Contributor
Posts: 1505

Loc: Lake George, NY
Reg: 11-11-15
11-12-18 03:43 PM - Post#2751189    
    In response to SandDabMcSkeg

Spring wrap up happens when accelerating from a dead stop, the forward section of the spring kind of winds upwards as a result of engine torque. This must be avoided either with antiwrap traction bars or stiffer front section of the rear spring or additional spring clamps, of course the torque tube prevents this.



 
johnwd98 
Contributor
Posts: 313
johnwd98
Age: 69
Loc: Little Falls, MN
Reg: 09-05-10
11-13-18 06:08 AM - Post#2751233    
    In response to Shepherd

Leaf springs are well known for spring wrap that causes wheel hop (especially when doing burn outs haha), but even without tire spin the rear diff. can twist upward causing strain on u joints. I used de-arced S-10 Blazer leaf springs (de-arced to lower the car). Left out the overload spring, I think that may have a mistake, as I have excessive spring wrap, and wheel hop. Don't know what to do, buy longer u bolts and reinstall the overload springs, or build some Caltrack style traction bars.

1950 Fleetline, 350 TBI, 700R4, 3.73 posi rear Blazer axle, MII front. Remote door and trunk locks, GM cruise control, A/C,


 
Mike JW 
"6th Year" Gold Supporting Member
Posts: 1334
Mike JW
Loc: Arroyo Grande, CA
Reg: 01-19-06
11-13-18 11:46 AM - Post#2751286    
    In response to johnwd98

I used Poises on my 50, but still had to add traction bars.



 
Shepherd 
Frequent Contributor
Posts: 1505

Loc: Lake George, NY
Reg: 11-11-15
11-13-18 11:54 AM - Post#2751287    
    In response to johnwd98

Clamp the front sections of the springs, old Mopar racer trick.



 
Bel Air kiwi 
"3rd Year" Silver Supporting Member
Posts: 4401
Bel Air kiwi
Loc: New Zealand
Reg: 04-24-14
11-13-18 12:53 PM - Post#2751290    
    In response to Shepherd

Hi Guys, Spring wrap occurs when the torque action in the driveline tries to rotate the diff head.

One way for acceleration, the other for braking.
The torque tube design eliminates this. Hence it's name. But to be fair, the forces an older car with torque tubes had to deal with were much smaller than modern vehicles and constrained by modest levels of traction.

The forces try and turn the axle housing and this requires that the spring adopts a flattened out "S" shape. The spring naturally resists this action and flexs back. This will give you the wheel hop or sometimes brake shudder effect.

Leaf springs are one of the worst systems for quick take offs available. However that is not a design parameter for OE vehicles.
They are there for comfort and smoothness.
The best system I know of that keeps the springs design functions and imroves traction is the "Caltrac". Old style slapper traction bars diminish spring function.

If you are increasing the speed of the vehicle a lot then for our cars you will need to improve the shock absorbers and fit a chassis x-member that takes their top mount out of the trunk floor.

What most people are missing is that often the two springs are operating differently. This matters a lot for tire clearance and part of body roll issues. Going for a wider spring of the same type greatly stifens its resistance to twisting along its axis.

The retro fit open driveline diff I prefer comes from a staion wagon. I use the whole thing, springs, shocks, bushes, handbrake cable lines etc. The old frame mounts go and new ones are made.
Unfortunately this assembly was not made in the US.

Cheers Kiwi






48 3100 RHD, 51 Deluxe 4DR RHD, 51 Bel Air parts car, 52 Bel Air P-Glide LHD. Others 23T, 32 Tudor, 58 Edsel pacer 4DR HDT, 79 F250 351C RHD. 69,70,82 Capri. No mobile, no TV, and no Jap cars.

"They made a desert and called it peace." Tacitus


Edited by Bel Air kiwi on 11-13-18 12:54 PM. Reason for edit: No reason given.

 

Chevs of the 40s

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