Trailing Arms - Buy or Rebuild? Std or Offset?
11-21-2017, 10:38 AM
#1
Pro
Thread Starter
Trailing Arms - Buy or Rebuild? Std or Offset?
1970 L46 Coupe. Driver with fresh, healthy motor and everything has been rebuilt, checked, changed and freshened from the radiator to the front of the rear end now. This winter will be the back half. It is bone stock. I am having the rear 3.36 gone through and re-geared to 3.70/3.73 and will replace the rear spring (steel multi-leaf) and will rebuild the half shafts myself.
Does it make the most sense to buy trailing arms and turn mine in as cores, or send my originals out for refurb by someone like VTech or Bairs? If I am going to the work, does it make the most sense to stick with a standard arm or go offset? Right now I am running slightly oversized tires on the stock rally rims, and likely will stick to that for some time. If I went offset for future flexibility, do I need to then run spacers or change out my wheels now?
Not new to cars at all, but learning the IRS as this is my first Corvette. The entire rear setup is foreign to me.
Side Note/Question: Is the IRS prone to wheel hop during hard launches (like traditional leaf spring cars)? If so, what is the best option to address wheel hop with this suspension.
Does it make the most sense to buy trailing arms and turn mine in as cores, or send my originals out for refurb by someone like VTech or Bairs? If I am going to the work, does it make the most sense to stick with a standard arm or go offset? Right now I am running slightly oversized tires on the stock rally rims, and likely will stick to that for some time. If I went offset for future flexibility, do I need to then run spacers or change out my wheels now?
Not new to cars at all, but learning the IRS as this is my first Corvette. The entire rear setup is foreign to me.
Side Note/Question: Is the IRS prone to wheel hop during hard launches (like traditional leaf spring cars)? If so, what is the best option to address wheel hop with this suspension.
Last edited by JoeMinnesota; 11-21-2017 at 10:38 AM.
11-21-2017, 10:46 AM
#2
Personally I would use the 47 year old arms as cores.
If you see tires in your future greater than 255 cross section go with offset and there is no issue with your current wheels
the traditional issue with wheel hop is because the spring twists with the solid axle. on the vette the spring is lateral to the forward motion and does not effect grip
If you see tires in your future greater than 255 cross section go with offset and there is no issue with your current wheels
the traditional issue with wheel hop is because the spring twists with the solid axle. on the vette the spring is lateral to the forward motion and does not effect grip
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JoeMinnesota (11-21-2017)
11-21-2017, 04:42 PM
#3
Race Director
I purchased new 2" offset trailing arms for my 73 from Van Steel and converted over to coil over rear suspension. I'll be running 8" wheels with a 4" backspace and don't need the offset, but thought, what if I want to go to a wider wheel down the road. Now I have the clearance.
11-21-2017, 05:25 PM
#4
Tech Contributor
Joe
The question what condition are your arms in? TA's rot from the inside out and get bent at alignment shops or accidents. If yours are shot then you won't get a core value on them and will need new arms. If you want to run a little wider tire without going to offset arms you can relocate the parking brake cable to the top of the arm and pickup some room.
If you are not racing, heavy shock loading the diff & IRS, then you can use stock 17 spline outer axles. If you are going to push it or build power over 450hp- very subjective rating by hp, then you might consider Tom's 31's while they are still available.
If your arms are in good shape why not rebuild them, either yourself if possible or send them out? People have been afraid of setting up TA's for years as if it's a black science or uses special bearings. They are not mystical and do not use special bearings. The problem faced by most is understanding the assembly & setting up the end play in the bearings correctly. With some instruction and access to a press and maybe a surface grinder they can be done at home. If that is not an option you select there are plenty of places that will rebuild them, as with all rebuild work the methods and procedures do vary.
If you have a local guy doing your diff then they should be able to do the arms too. BTW, 370 was the original GM ratio not 373 but the only new usa made gears are 373. 370's are imported. There is no performance difference but the 373 are better and what I use. If you haven't bought them yet expect to find they are now 2 cut gears- not as good as the old 5 cut.
The question what condition are your arms in? TA's rot from the inside out and get bent at alignment shops or accidents. If yours are shot then you won't get a core value on them and will need new arms. If you want to run a little wider tire without going to offset arms you can relocate the parking brake cable to the top of the arm and pickup some room.
If you are not racing, heavy shock loading the diff & IRS, then you can use stock 17 spline outer axles. If you are going to push it or build power over 450hp- very subjective rating by hp, then you might consider Tom's 31's while they are still available.
If your arms are in good shape why not rebuild them, either yourself if possible or send them out? People have been afraid of setting up TA's for years as if it's a black science or uses special bearings. They are not mystical and do not use special bearings. The problem faced by most is understanding the assembly & setting up the end play in the bearings correctly. With some instruction and access to a press and maybe a surface grinder they can be done at home. If that is not an option you select there are plenty of places that will rebuild them, as with all rebuild work the methods and procedures do vary.
If you have a local guy doing your diff then they should be able to do the arms too. BTW, 370 was the original GM ratio not 373 but the only new usa made gears are 373. 370's are imported. There is no performance difference but the 373 are better and what I use. If you haven't bought them yet expect to find they are now 2 cut gears- not as good as the old 5 cut.
11-21-2017, 05:29 PM
#5
Tech Contributor
There are traction bars made for this IRS, if you start launching hard with a stock diff & IRS you may find that you will be revisiting it again in the future. Hard launches tear into everything south of the flywheel and your weak links will show up- posi case, 17 spline axle, snubber bracket, twisted slip yoke & driveshaft, and broken u-joints - we experienced them all at the track at one time or another.
11-23-2017, 09:55 AM
#6
Pro
Thread Starter
Joe
The question what condition are your arms in? TA's rot from the inside out and get bent at alignment shops or accidents. If yours are shot then you won't get a core value on them and will need new arms. If you want to run a little wider tire without going to offset arms you can relocate the parking brake cable to the top of the arm and pickup some room.
If you are not racing, heavy shock loading the diff & IRS, then you can use stock 17 spline outer axles. If you are going to push it or build power over 450hp- very subjective rating by hp, then you might consider Tom's 31's while they are still available.
If your arms are in good shape why not rebuild them, either yourself if possible or send them out? People have been afraid of setting up TA's for years as if it's a black science or uses special bearings. They are not mystical and do not use special bearings. The problem faced by most is understanding the assembly & setting up the end play in the bearings correctly. With some instruction and access to a press and maybe a surface grinder they can be done at home. If that is not an option you select there are plenty of places that will rebuild them, as with all rebuild work the methods and procedures do vary.
If you have a local guy doing your diff then they should be able to do the arms too. BTW, 370 was the original GM ratio not 373 but the only new usa made gears are 373. 370's are imported. There is no performance difference but the 373 are better and what I use. If you haven't bought them yet expect to find they are now 2 cut gears- not as good as the old 5 cut.
The question what condition are your arms in? TA's rot from the inside out and get bent at alignment shops or accidents. If yours are shot then you won't get a core value on them and will need new arms. If you want to run a little wider tire without going to offset arms you can relocate the parking brake cable to the top of the arm and pickup some room.
If you are not racing, heavy shock loading the diff & IRS, then you can use stock 17 spline outer axles. If you are going to push it or build power over 450hp- very subjective rating by hp, then you might consider Tom's 31's while they are still available.
If your arms are in good shape why not rebuild them, either yourself if possible or send them out? People have been afraid of setting up TA's for years as if it's a black science or uses special bearings. They are not mystical and do not use special bearings. The problem faced by most is understanding the assembly & setting up the end play in the bearings correctly. With some instruction and access to a press and maybe a surface grinder they can be done at home. If that is not an option you select there are plenty of places that will rebuild them, as with all rebuild work the methods and procedures do vary.
If you have a local guy doing your diff then they should be able to do the arms too. BTW, 370 was the original GM ratio not 373 but the only new usa made gears are 373. 370's are imported. There is no performance difference but the 373 are better and what I use. If you haven't bought them yet expect to find they are now 2 cut gears- not as good as the old 5 cut.
The car has never been hit, aligned well and is generally in very good condition. Maybe I should leave the TA's alone, or just do the bushings. It's a "while I have the rearend out" plan as I have not been through the back half of the car yet. Maybe I'll pull them and take them in with the rearend and simply keep the same arms.
11-23-2017, 02:49 PM
#7
vette
Under high RPM launches the rear diff wants to spring up towards the tunnel at the front support bracket located at the rear of the drive shaft and front of the rear. Launching at 6k can sheer off the bolts on that bracket. I made a traction bar with a plate to reinforce that area.
RVZIO
Oh , I went with new Vansteel stock units .
RVZIO
Oh , I went with new Vansteel stock units .
Last edited by SB64; 11-23-2017 at 02:50 PM.
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JoeMinnesota (11-23-2017)
11-23-2017, 06:34 PM
#9
Tech Contributor
If your arms are rotted or bent I would NOT resuse them. If you have a cut wheel and welder you can relocate the bracket to the arm. You can check the endplay in the bearing by grabbing a wheel stud to see if you can push/pull on it and have movement. If you feel it then will be about 003+ while in spec I always set mine tighter.
I can post pictures if it helps you.
I can post pictures if it helps you.
Last edited by GTR1999; 11-23-2017 at 09:37 PM.
11-23-2017, 09:05 PM
#10
Pro
Thread Starter
If your arms are rotted or bent I would resuse them. If you have a cut wheel and welder you can relocate the bracket to the arm. You can check the endplay in the bearing by grabbing a wheel stud to see if you can push/pull on it and have movement. If you feel it then will be about 003+ while in spec I always set mine tighter.
I can post pictures if it helps you.
I can post pictures if it helps you.
The shop that did my alignment was pretty picky about the bearings and other parts (I ended up repacking the fronts and doing the strut arms). I think if the TA's were a mess they would have called them out.
11-23-2017, 09:36 PM
#11
Tech Contributor
Here is my old link here, I didn't go through it to recheck it but I think the pictures are still up. My previous response should have read I wouldn't reuse bent or rotted arms
https://www.corvetteforum.com/forums...n-rebuild.html
https://www.corvetteforum.com/forums...n-rebuild.html
11-24-2017, 05:54 AM
#12
Race Director
All of your pics are there. When people hit reply-most I think not realizing they are reposting your post pics and all-the pics are not there in their repost.