# Need help with my Torsion bars...



## Chevy/GMC (Dec 2, 2009)

Ok I just bought this truck a week ago and I'm getting ready to swap out my Boss 7.6 std poly from my 97 1/2 ton GMC to my 06 HD CC Duramax. The question I have is?? Is there away to tell if the torsion bars have already been turned up? To me it looks like the front end of my 06 sits up alittle higher then my father-in-laws 05 HD ext cab Chevy. Here is a picture of my 06. I ordered a set of Buyers timbrens through Northern yesterday they should be here next week. I'd really like to know if there is a way to tell if the previous own did anything to the torsion bars.The tires are 265 75's. I'd also like to know if a set of 285's would give me any problems up front??


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## 2COR517 (Oct 23, 2008)

That looks like it's sitting pretty level to me, but you might be able to go up an inch or so. I don't think there is any way to tell, unless one or both of the adjusting screws are bottomed out. I think you'll be fine, especially with your load boosters in.


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## mossman381 (Nov 17, 2009)

You could measure your fenders. The rear should be about 2" or so higher than the front from the factory. It is really hard to tell from the pic.


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## Chevy/GMC (Dec 2, 2009)

Ok thanks, I will do some measuring today to see where I'm at. I just don't want to tighten them to much. This truck rides like a car compared to my 97 1/2 ton. But I don't want it sagging looking like a big puss with my little STR BLD, if you know what I mean???


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## JCByrd24 (Oct 19, 2005)

The real way to tell is by measuring what GM refers to as Z-height. Do the following on a hard, fairly level surface:

1) Measure ground to front, lower control arm bolt (center).
2) Measure ground to the top side of the lower ear on the steering knuckle.

Subtract measurement 2 from 1. I believe the spec for this is 4.3" to 4.8" for all trucks (1500, 2500, etc), I can't find it online specifically for HDs, so maybe call the dealer, z-height is the name that GM uses either way. Much more accurate than a fender/bumper measurement because it disregards tire size/pressure/etc. On my 1500 I leveled 1.5" and still was only at 4.5" z-height, I think 1500s especially are usually low from the factory.


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## stacks04 (Jan 22, 2008)

if it is factory set the adjuster bolts will be lower than the actual cross member. meaning the bolt will stick out past the cross member slightly. i doubt they are still set to factory height. the truck is sitting nicely. good luck with the new truck.


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## mossman381 (Nov 17, 2009)

JCByrd24;935107 said:


> The real way to tell is by measuring what GM refers to as Z-height. Do the following on a hard, fairly level surface:
> 
> 1) Measure ground to front, lower control arm bolt (center).
> 2) Measure ground to the top side of the lower ear on the steering knuckle.
> ...


That is some really good info.


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## BigLou80 (Feb 25, 2008)

Chevy/GMC;934741 said:


> Ok I just bought this truck a week ago and I'm getting ready to swap out my Boss 7.6 std poly from my 97 1/2 ton GMC to my 06 HD CC Duramax. The question I have is?? Is there away to tell if the torsion bars have already been turned up? To me it looks like the front end of my 06 sits up alittle higher then my father-in-laws 05 HD ext cab Chevy. Here is a picture of my 06. I ordered a set of Buyers timbrens through Northern yesterday they should be here next week. I'd really like to know if there is a way to tell if the previous own did anything to the torsion bars.The tires are 265 75's. I'd also like to know if a set of 285's would give me any problems up front??


nice looking truck. If you don't mind me asking what did you pay for that ? I am going to be looking for a truck just like that in the spring


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## mossman381 (Nov 17, 2009)

JCByrd24;935107 said:


> The real way to tell is by measuring what GM refers to as Z-height. Do the following on a hard, fairly level surface:
> 
> 1) Measure ground to front, lower control arm bolt (center).
> 2) Measure ground to the top side of the lower ear on the steering knuckle.
> ...


Well, I went out to turn my t-bars up a bit. So I put it on the hoist and noticed right away that the driver side bolt was in alot more than the passenger side. I gave them each 1 1/2 turns. Another thing I noticed was how easily the bolts turn. Was not expecting that. Drop it on the ground back it up and foward a few times and measured the height. I only gained 3/4" And the truck was more unlevel than it was. I wanted about 1" of lift and level side to side, so I ended up turning the driver side 3 turns and the passenger side 2 turns. I measured from the ground to the center of the lower control arm bolt and it was 13 1/4". I then measured from the ground to the top side of the lower ear on the steering knuckle and it was 10 1/2". That would give me a z-height of 2 3/4". I really don't think you could get the z-height to be 4.3" on my truck. Right now I am happy with the 1" lift I got. When I raise my plow I am at the same height I was from the factory. Anybody know the z-height of an 08 2500 HD?

If you look at the pic there is no way that truck has a 4" z-height. I am thinking the z-height must be 2.3" to 2.8".


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## JCByrd24 (Oct 19, 2005)

mossman, I would guess the 08 is different than the 99-07classic, totally redesigned right? Call the dealer and see what they say. Also, that pic is from a BDS supsension install manual, and BDS shoots for 4", a little less than stock specs for better CV angles I'm guessing, but I cannot speculate what the actual z-height in that picture is.

I can tell you that my 1500 is at 4.5" and it looks similar to the pic, the 2500HD and/or 2008 may have different specs.


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## Chevy/GMC (Dec 2, 2009)

BigLou80;936188 said:


> nice looking truck. If you don't mind me asking what did you pay for that ? I am going to be looking for a truck just like that in the spring


No I don't mind at all. The dealer I bought it from had it on the lot for $32,995 
After it was all said and done I traded my wife's 01 Mustang GT and gave them $20,000 difference. The truck was a one owner with 53,000 miles on it and looks drives like it's new. Here is the Mustang I traded in


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## Newdude (Dec 4, 2006)

JCByrd24;936375 said:


> mossman, I would guess the 08 is different than the 99-07classic, totally redesigned right? Call the dealer and see what they say. Also, that pic is from a BDS supsension install manual, and BDS shoots for 4", a little less than stock specs for better CV angles I'm guessing, but I cannot speculate what the actual z-height in that picture is.
> 
> I can tell you that my 1500 is at 4.5" and it looks similar to the pic, the 2500HD and/or 2008 may have different specs.


The GMT-900 frame is very much a GMT-800 frame, with some new body mounts, and not much more.

GMT-900 specs are as follows:

C/K2500 
w/o ZW9
110-122 mm (4.3-4.8 in)Service Allowed
116 mm (4.5 in)Service Preferred

C/K2500
w/ZW9
100-112 mm (3.9-4.4 in)Service Allowed
106 mm (4.2 in) Service Preferred

RPO ZW9 = Base Body/ Chassis

GMT-800 are as follows:

C/K 2500:
110-122 mm (4.3-4.8 in) Service Allowed
116 mm (4.5 in) Service Preferred


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## mossman381 (Nov 17, 2009)

There is no way I could get my z-height to be 4". I could crank my t-bars all the way up and never get it over 4". Can someone else measure their new HD and see what you come up with? I am going to the shop right now and measure again.


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## Newdude (Dec 4, 2006)

Steps for measuring acccording to GM:

1: Jounce the front suspension of the vehicle by pushing the vehicle down and lifting up.

2: Allow the vehicle to settle and take a measurement.

3: Set the top edge of the level on the reference surface of the steering knuckle and extend the level directly under the front end of the front attachment bolt of the lower control arm.

4: While keeping the level in contact with the knuckle reference surface, adjust the level up/down until the bubble indicates it is horizontally level.

5: Measure the distance between the center of the bolt and the top of the level for your first measurement.

6: Keep the top edge of the level on the reference surface of the steering knuckle and move the level directly under the rear end of the rear attachment bolt of the lower control arm.

7: Measure the distance between the center of the bolt and the top of the level for your second measurement.

8: Average the measurements between the step 6 and step 8.

9: Record the measurement.

Any aftermarket modifications could affect the results of the numbers also. The very bottom of the steering knuckle should be the base refrence point for the measurements.


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## mossman381 (Nov 17, 2009)

No matter which way I measure I am still getting 2.75". Something is wrong. 2.75" is after I have turned up my bars a bit. Any info would be appreciated.


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## RichG53 (Sep 16, 2008)

JCByrd24;935107 said:


> The real way to tell is by measuring what GM refers to as Z-height. Do the following on a hard, fairly level surface:
> 
> 1) Measure ground to front, lower control arm bolt (center).
> 2) Measure ground to the top side of the lower ear on the steering knuckle.
> ...


I guess I have a disagreement about your measurement from knuckle to ground..Tire size and inflation will affect this measurement a long with the lower control arm bolt...
Unless you left some thing out in your explanation or I missed some thing...


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## yamahartx (Dec 24, 2009)

Chevy/GMC;934741 said:


> Ok I just bought this truck a week ago and I'm getting ready to swap out my Boss 7.6 std poly from my 97 1/2 ton GMC to my 06 HD CC Duramax. The question I have is?? Is there away to tell if the torsion bars have already been turned up? To me it looks like the front end of my 06 sits up alittle higher then my father-in-laws 05 HD ext cab Chevy. Here is a picture of my 06. I ordered a set of Buyers timbrens through Northern yesterday they should be here next week. I'd really like to know if there is a way to tell if the previous own did anything to the torsion bars.The tires are 265 75's. I'd also like to know if a set of 285's would give me any problems up front??


Your torsion's are turned somewhere between 3-4 turns already. It might not need any more then that. I would put the plow on and check before changing anything.

Looks like mine, 3 turns with 285's Only rubs when backing and cranking the wheel hard with plow on. 700lb plow


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## mossman381 (Nov 17, 2009)

RichG53;942085 said:


> I guess I have a disagreement about your measurement from knuckle to ground..Tire size and inflation will affect this measurement a long with the lower control arm bolt...
> Unless you left some thing out in your explanation or I missed some thing...


Tire size wouldn't make a difference. If you had bigger tires then all the measurements would be bigger. When you minus the two you will still come up with the same as using the level. This is not the most exact way to do it, but it will get the job done.


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## Newdude (Dec 4, 2006)

mossman381;941863 said:


> No matter which way I measure I am still getting 2.75". Something is wrong. 2.75" is after I have turned up my bars a bit. Any info would be appreciated.


Try this from my post with the drawing...



Newdude;939994 said:


> Steps for measuring acccording to GM:
> *8: Average the measurements*


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## B&B (Nov 4, 2006)

mossman381;939794 said:


> There is no way I could get my z-height to be 4". I could crank my t-bars all the way up and never get it over 4".





mossman381;941863 said:


> No matter which way I measure I am still getting 2.75". Something is wrong. 2.75" is after I have turned up my bars a bit. Any info would be appreciated.





mossman381;941863 said:


> I then measured from the ground to the top side of the lower ear on the steering knuckle


 I see what your issue is. You measuring from the TOP of the steering knuckle and thats not correct when checking Z-height. You measure from the BOTTOM (see attached pic). Also, the T900's use the same Z-height spec as the previous generation T800's so you should have been around 4.5" with the original T-bar settings, just as a stock T800.

You also don't measure from the ground. You measure from the parallel you're using (a 3 ft bubble level works well) on the steering knuckle up to the center pivot bolt. No math involved.


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## 2COR517 (Oct 23, 2008)

B&B;943766 said:


> You also don't measure from the ground. You measure from the parallel you're using (a 3 ft bubble level works well) on the steering knuckle up to the center pivot bolt. No math involved.


Just to clarify, and be sure I understand......

With the truck sitting on a level surface. Place a carpenter's level on the lowest point of the steering knuckle. When the bubble in the level is centered, simply measure from the center of the lower control arm pivot bolt to the top of your level. The number should be in the 4" neighborhood.

I would make a pic, but can't find a decent pic of a level right now.

Is this spec the same for GMT 400 trucks?


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## B&B (Nov 4, 2006)

2COR517;943782 said:


> Just to clarify, and be sure I understand......
> 
> With the truck sitting on a level surface. Place a carpenter's level on the lowest point of the steering knuckle. When the bubble in the level is centered, simply measure from the center of the lower control arm pivot bolt to the top of your level. The number should be in the 4" neighborhood.
> 
> ...


Correct.

And here's the T400 OBS specs too...


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## JCByrd24 (Oct 19, 2005)

Sorry for bad information, the only place I'd ever found an explantion was a set of BDS suspension lift install instructions. They are going to the top of the knuckle ear, but at 4", which would still be over factory I think, but it's also a replacement knuckle so who knows. I need to check mine again!!


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## mossman381 (Nov 17, 2009)

Well, I measured from the bottom of the steering knuckle and I am about 4". That sounds more like it. With that I am still 1/2" to low. And this is after I turned up my bars up 3 turns. Are you guys sure that the z-height is 4.5" for the 08 HD. If it is, I might turn mine up another turn. Here is a pic.


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## Newdude (Dec 4, 2006)

C/K2500 

110-122 mm (4.3-4.8 in)Service Allowed
116 mm (4.5 in)Service Preferred


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## B&B (Nov 4, 2006)

Give it another turn or two. No harm.

FYI, many many trucks come off the lot BELOW the correct Z-spec.


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