Axle aligment after axle swap

[K10blueChevy]

Hey Guys,
I just finished up swapping axles on a 83k10. Bye Bye 2.73 hello 3.73 posi. The truck actually drives like it should again with these 33" tires on it.



Question: What is the best spot on the frame to measure from to ensure the front and rear axles are square to the frame?


Backstory: I should have measured the distance from front axle to back axle before I removed the factory axles, but I wasn't thinking that far ahead at that time. Anyway, I had to remake the spring locating pins for both front spring packs, they were both broken.

Anyway I did a quick measurement, rim to rim once the wheels were back on it and I was off 3" between drivers side to passenger side. The truck was not setting completely level but 3" seems a lot.

Before the axle swap, under braking and making a right hand turn the passengers front tire would pull the chrome from the fender. I haven't driven the truck enough yet to know if this was remedied with a new spring pin.

Thanks for any advice provided.

 

[TravisB]

Hey Guys,
I had to remake the spring locating pins for both front spring packs, they were both broken.

Disclaimer: I am no professional and use this as just and educated guess. My confidence in the below solutions goes from high with number to seek a second opinion before you do anything on 2 and 3.

This could be interpreted several ways. I have 3 possibilities in mind.

1. Are you saying you had to put new pins through the leaf springs that hold the pack together?
2. Or that you had to make or weld new spring pads on the axle tube?
3. Or you had to make new hangers on the frame for the leaf springs?

If number 1 and you just put new pins in the spring pack you wouldn't have changed anything that I would worry about.

However, if you welded new pads on the tubes or new hangers on the frame there is some room for error there.

If we are talking the second one, I don't think you could have changed any front to back measurements so you need to make sure you have equal measurements right and left to the frame. I would get the wheels off and use the end of the axle tube to spring and or frame measurement on each side and compare to make sure it was centered under the truck. Try to avoid measuring to the wheel or rotor or something unless you measure in front and back both since that twists around if you turn the wheel. If your frame is straight, and you get equal measurements you are probably fine with the centering. Then there is the pinion angle you will probably want to check as well to make sure you got that close to where it was. There is a Tremec app for your phone that will help you do that if you don't know how. http://tremec.com/menu/tremec-toolbox-app/

Now number three, this is where you have the most room for error. Not only do you need to measure left and right but now you have front to back issues to worry about. The same deal as above for left and right but don't use the spring as a reference. It could be wrong, you will need to use the frame. You will also want to measure spring to frame in front and behind too to make sure it's parallel with the frame. If you are off there you know you need to cut the hangers off and fix that. For front to back I would measure from the front axle to the back on both sides and make sure that is equal and then go corner to corner to make sure it's square. If your measurements front to back on each side are off or the corner to corner measure is off you will probably need to cut it apart and square it up.

 

[TravisB]

On Second read through, can you explain this more?

rim to rim once the wheels were back on it and I was off 3" between drivers side to passenger side. The truck was not setting completely level but 3" seems a lot.

That could be a simple alignment thing if you measured front of the wheel to the front of the wheel on the other side. 3 inches is a lot to drive it like that but you can adjust that out in the tie rods. To get it close measure the distance on the rear of the wheel to the rear of the wheel on the other side and compare that to the measurement on the front side. Then adjust it until they match each other and take it to an alignment shop for fine tuning. There are videos on youtube to do this just search toe alignment at home and you will find several.

 

[TravisB]

Oh, and post some pics of what you did or your measurements and I am sure we can sort it out.

 

[K10blueChevy]

Disclaimer: I am no professional and use this as just and educated guess. My confidence in the below solutions goes from high with number to seek a second opinion before you do anything on 2 and 3.

This could be interpreted several ways. I have 3 possibilities in mind.

1. Are you saying you had to put new pins through the leaf springs that hold the pack together?
2. Or that you had to make or weld new spring pads on the axle tube?
3. Or you had to make new hangers on the frame for the leaf springs?

If number 1 and you just put new pins in the spring pack you wouldn't have changed anything that I would worry about.

.

I did #1. Spring pin was broken. Tried drilling out the springs to upgrade to a 3/8" grade 8 bolt but found out the springs were harder than my drill bit. So I opted for a M8 12.5 hex and turned the head down.

To clarify my measurement that I took. I measured from the rear rim edge to the front rim edge on each side of the truck. The numbers were off by 3" with the short side being the passenger measurement. I replaced both axle assemblies, front and rear. The spring pins were broken on both front axles spring packs.

 

[TravisB]

I did #1. Spring pin was broken. Tried drilling out the springs to upgrade to a 3/8" grade 8 bolt but found out the springs were harder than my drill bit. So I opted for a M8 12.5 hex and turned the head down.

To clarify my measurement that I took. I measured from the rear rim edge to the front rim edge on each side of the truck. The numbers were off by 3" with the short side being the passenger measurement.

Okay, replacing the pins in the pack shouldn't change anything imo.

So if I gather this right you made this measurement. Imagine a drone looking down on your truck.


DR ------- DF

PR ------- PF


So you measured along the dotted line where DR and DF are drivers rear and drivers front and then PF and PR are Passenger front and rear?

This could be weird because you were on uneven ground or had the wheel turned a little when you measured it. To make sure you don't have an issue get it on some concrete level surface and measure axle tube to axle tube and use the spring perch as a reference on each side. 3 inches seems like a lot but if wheel to wheel and you had it turned a little the measurement will double. So if you had the wheel turned and it was 1.5 inches forward on the drivers side it would be 1.5 back on the passenger side and would give you the the 3 inch difference. The tubes should be pretty solid but the springs flex so even that could be a little off even on level ground but it takes a lot of the error out.

 

[K10blueChevy]

Okay, replacing the pins in the pack shouldn't change anything imo.

So if I gather this right you made this measurement. Imagine a drone looking down on your truck.


DR ------- DF

PR ------- PF


So you measured along the dotted line where DR and DF are drivers rear and drivers front and then PF and PR are Passenger front and rear?
.

Yes Exactly correct.



Ok, I think the wheels were fairly straight when I took the measurement, but I know the drivers rear was on higher ground when measuring.

To Play Mr. Negative.....
If I get it on level ground with the wheels aligned straight ahead and retake this measurement and I'm still off then what? Measure from spring perch to leaf spring mounts?

I did notice on the passenger side of the frame almost right below the firewall where the frame Z up to the motor mounts there is a spot where the paint (or some coating) is peeling off. To me it looks like a plastic fender that was bent and now the paint is stress cracking and falling off. This is just on the lower inside radius. The top of the frame looks fine. I'll try to get a picture. Just made me wonder if the frame wasn't bent, or took a hit there. I know there is a ton of bondo in that passenger door. The joys of buying a used vehicle of unknown history.

 

[TravisB]

Yes Exactly correct.



Ok, I think the wheels were fairly straight when I took the measurement, but I know the drivers rear was on higher ground when measuring.

To Play Mr. Negative.....
If I get it on level ground with the wheels aligned straight ahead and retake this measurement and I'm still off then what? Measure from spring perch to leaf spring mounts?

I did notice on the passenger side of the frame almost right below the firewall where the frame Z up to the motor mounts there is a spot where the paint (or some coating) is peeling off. To me it looks like a plastic fender that was bent and now the paint is stress cracking and falling off. This is just on the lower inside radius. The top of the frame looks fine. I'll try to get a picture. Just made me wonder if the frame wasn't bent, or took a hit there. I know there is a ton of bondo in that passenger door. The joys of buying a used vehicle of unknown history.

Yeah if your measurements are off from the front to back axle then I would think something is up. I have never measured it but I can't see how you could have moved it 3 inches unless you just didn't put the pin in the spring pad when you put the axle back under the truck. I've never straightened a frame myself but I have seen it done and worked in a garage with a frame rack for a while. I believe there are specific places to measure to make sure you are in spec but I've seen guys just find some spots to measure from. For example a bump stop mount to the trans mount on each side and then diagonally between them to make sure it's square. It will be a chore to track down for sure if you have a bend in the frame. A 4 post lift will help if you have access to one so you can get some accurate measures but it can be done on the ground. Post some pics and there are probably other guys on here that can help as well.

 

[Curt]

You have a spring on backwards

 

[BKING33]

Best way to do on alignment rack. I had TK that was off 1/4" use can get it close pulling measurements from frame. Then get alignment done to fine tune it