Diesel Place banner

21 - 40 of 40 Posts

·
Gone but not forgotten member
Joined
·
2,582 Posts
If the bars would have been cranked you would have a large gap. If anything the torsion bars are sagging with age. The only way to know for sure is to know the factory ride height spec. which is the distance between one of the control arms and the full extension metal stop . To make you tires last the longest have the alignment done.
 

·
Registered
Joined
·
388 Posts
Discussion Starter #22
If the bars would have been cranked you would have a large gap. If anything the torsion bars are sagging with age. The only way to know for sure is to know the factory ride height spec. which is the distance between one of the control arms and the full extension metal stop . To make you tires last the longest have the alignment done.
Ah, ok -- cranked means large gap. Alignment here I come.
 

·
Registered
Joined
·
1,000 Posts
What differences in handling/suspension characteristics do the Z71 jounce bumpers provide over the standard bumpers. Seems everytime I read one of these threads, guys just say they are 'Better'. Better in what way?
 

·
Registered
Joined
·
388 Posts
Discussion Starter #24
What differences in handling/suspension characteristics do the Z71 jounce bumpers provide over the standard bumpers. Seems everytime I read one of these threads, guys just say they are 'Better'. Better in what way?
Not sure I can answer your question technically but I can say they did improve my ride. It still rides like a 3/4 ton truck but the front end seems to ride a bit smoother. Worth the effort in my opinion to replace.

That being said the old Oem ones were toast and looked to be made of a hard "foam". The z71 ones are made of some sort of poly. I'm not sure if I would have seen the same ride improvement by going back with Oem or not - guess i will never know.
 

·
Registered
Joined
·
87 Posts
CV angle?

From the looks of it, your front differential cv is higher than your wheel bearing center. This would indicate your truck has been lowered.

When the torsion keys have been cranked up, the differential is noticeably higher than the wheel center and the front drive axels slope noticeably down. Your axles are parallel with the ground or maybe even angled up towards the wheel. Your truck has been lowered not lifted if I see the pictures correctly.

There is an alignment spec called Zheight. It is measured from the ground to the bottom of the torsion key mounting bar, however taller tires are going to throw this factory spec out of wac.

Just crank your tbar adjusters till there is about 1/4 inch between each bumstop and arm. You can then measure from ground to frame and see if each side is the same.
 

·
Gone but not forgotten member
Joined
·
2,582 Posts
Thanks Lazy03, the 1/4 gap at the jounce/bumpstops/whatcamacalits. My old school front end mechanic told me the same thing and this is why, let the torsion bars and shocks do their jobs that 1/4 amounts to at least an inch or more of travel at the wheel centerline and makes for a smoother ride.
 

Attachments

·
Registered
Joined
·
388 Posts
Discussion Starter #27
From the looks of it, your front differential cv is higher than your wheel bearing center. This would indicate your truck has been lowered.

When the torsion keys have been cranked up, the differential is noticeably higher than the wheel center and the front drive axels slope noticeably down. Your axles are parallel with the ground or maybe even angled up towards the wheel. Your truck has been lowered not lifted if I see the pictures correctly.

There is an alignment spec called Zheight. It is measured from the ground to the bottom of the torsion key mounting bar, however taller tires are going to throw this factory spec out of wac.

Just crank your tbar adjusters till there is about 1/4 inch between each bumstop and arm. You can then measure from ground to frame and see if each side is the same.
Thanks, lazy03. I think you may be right. I had my truck in to the dealership for the install of the MA pump upgrade kit and had them do the alignment while it was there. The tech came back out and asked me if the front had ever been lowered and said that the jounces were riding on the lower control arms. He raised it back up. I checked his work and noticed that the drivers side had a 1/4 inch gap between the jounce and LCA and the passenger side was still touching. I asked him about that and said that he could not crank it anymore or it would be out of spec and must have something to do with the frame.

Then he asked if the truck had been pulling (can't recall which direction) because one of the wheels was out of whack.

Well on the way home I noticed the truck was pulling to the right pretty hard. I was straight as an arrow before the alignment so something is definitely not right. I'll be heading back to get them to correct it.

I guess all else being equal pulling to the right make sense b/c the drivers sides, as judged by the gap between the jounce and lca, is higher the passenger side.

Any thoughts on what might be the issue?

The gap between the top of the tire and the bottom of the wheel well is definitely bigger than before and looks to be equal to the rear wheels. I'm not sure if that right or not -- other 2500's on the road don't look to have equal gaps on the front and back.
 

·
Gone but not forgotten member
Joined
·
2,582 Posts
The dealers and other shops that use the laser guided gizmo gadget watchamacalits to set these front end do not impress me at all. My opinion, these front ends need to be set by the seat of the pants with your mitts on the wheel and sometimes by the weight you have in the bed of lack of, mine had around 1800 lbs. I have been fortunate with two old school front end shops where I live, one retired over 10 years ago and the other shop has two brothers. They knew what the specs were BUT set the front end by the way it drives down the road.

The one with the two brothers goes like this. Pull into the small lot, one will walk up to you and ask couple questions take your keys and drive around block. Pull it over the 30x40 pit set the front end if you have no worn parts. Had the dealer set my 07 2500HD gasser 3 times while under warranty and still drove like a snake on the highway. When I had the brothers shop align it straight as an arrow.

The gap you are talking about is correct and should be equal, mine was raised quite a bit when it was done. Has the truck ever been in a serious front end accident? Are the torsion bars sagging? If you know some one at a bank they can pull a car fax sheet for free or pay for it online to see your trucks accident history.
 

·
Registered
Joined
·
388 Posts
Discussion Starter #29
The dealers and other shops that use the laser guided gizmo gadget watchamacalits to set these front end do not impress me at all. My opinion, these front ends need to be set by the seat of the pants with your mitts on the wheel and sometimes by the weight you have in the bed of lack of, mine had around 1800 lbs. I have been fortunate with two old school front end shops where I live, one retired over 10 years ago and the other shop has two brothers. They knew what the specs were BUT set the front end by the way it drives down the road.

The one with the two brothers goes like this. Pull into the small lot, one will walk up to you and ask couple questions take your keys and drive around block. Pull it over the 30x40 pit set the front end if you have no worn parts. Had the dealer set my 07 2500HD gasser 3 times while under warranty and still drove like a snake on the highway. When I had the brothers shop align it straight as an arrow.

The gap you are talking about is correct and should be equal, mine was raised quite a bit when it was done. Has the truck ever been in a serious front end accident? Are the torsion bars sagging? If you know some one at a bank they can pull a car fax sheet for free or pay for it online to see your trucks accident history.
When I bought the truck the carfax was clean.

Not sure how to know if the torsion bars are sagging or not. Is there a way to measure that?

Maybe the tech just missed something. Either way I'll be discussing w/ the service manager and making sure this is done right or my money is refunded.
 

·
Gone but not forgotten member
Joined
·
2,582 Posts
When I bought the truck the carfax was clean.

Not sure how to know if the torsion bars are sagging or not. Is there a way to measure that?

Maybe the tech just missed something. Either way I'll be discussing w/ the service manager and making sure this is done right or my money is refunded.
Maybe some one else will chime in, if your T-bar bolts are bottomed out to preload the tension that might be a good indicator they have lost their spring.....here is a picture of mine.
 

Attachments

·
Premium Member
Joined
·
17,839 Posts

·
Registered
Joined
·
287 Posts
Here are some pics of the new Z71 jounce / bump stops installed.

You can see these definitely, but barely, touch the LCA's. There is most definitely not a 1/4" gap.

As such I would assume my torsion bars have been cranked -- would you agree? Could there by any other explanation? Old/bad shocks?

Perhaps a visit to an alignment shop is in my near future to get the front set back to spec (or adjusted to fit 265's).

Driver's side
I'm having the same issue with my 2004.5 Duramax and I need to replace mt two bumperstops. Do you have a part number for the Z71 replacement stops and where to buy them?

Thanks..
 

·
Bac To The Future
Joined
·
23,029 Posts
15835667
 

·
Registered
Joined
·
1,375 Posts
I got mine from Merchant Automotive; Z71 style 15835667 is part # 10418 $55 two weeks ago.
 

·
Registered
Joined
·
388 Posts
Discussion Starter #35
Bac and surge beat me to the punch. That is the part number I showed well. I ordered mine from gmpartsdirect two yrs ago for $16.47 a piece.
 

·
Registered
Joined
·
287 Posts

·
Registered
Joined
·
290 Posts
What differences in handling/suspension characteristics do the Z71 jounce bumpers provide over the standard bumpers. Seems everytime I read one of these threads, guys just say they are 'Better'. Better in what way?
They look similar to the S10 ZQ8 bumpstops that are popular swaps for G-bodies. The bump stop is progressive (there is less "spring rate" at the tapered end, and as it gets squished, there is more cross-sectional area to provide resistance.) It's not just a hard rubber bumper to keep the suspension from smacking the frame.
 

·
Registered
Joined
·
287 Posts
They look similar to the S10 ZQ8 bumpstops that are popular swaps for G-bodies. The bump stop is progressive (there is less "spring rate" at the tapered end, and as it gets squished, there is more cross-sectional area to provide resistance.) It's not just a hard rubber bumper to keep the suspension from smacking the frame.
I just replaced my old stock "Bump Stops" with the Z71 ones and the truck "Seems" to handle better but I'm sure it's all in my head lol. However, I don't see the harm in replacing the stock stops with the Z71's..
 

·
Registered
Joined
·
287 Posts
21 - 40 of 40 Posts
Top