rear end thrust angle

little red cheroke · Mar 6, 2006

first off i know this has probly been coverd before on the fourms but im at school and dont have time to search through threads for an answer. sorry in advance. and i need to get a solution fast cuz this is starting to wear my tires and its killing my gas mileage.

i got an alignment today and they said my rear end was out. they said my jeep had been wrecked or something and my axle was sitting crooked. my thrust angle specified range is -0.15* to 0.15* and my before angle was
-0.42* and now its at -0.40*. could that be caused by lift or degre shims? if it was why didnt any body say something about it on the previous alignments? i didnt know you could align an axle on leaf springs. they said to fix it take it to a body shop or something. any body know whats goin on with my rear axle

thanks

Kejtar · Mar 6, 2006

little red cheroke said:
first off i know this has probly been coverd before on the fourms but im at school and dont have time to search through threads for an answer. sorry in advance. and i need to get a solution fast cuz this is starting to wear my tires and its killing my gas mileage.

i got an alignment today and they said my rear end was out. they said my jeep had been wrecked or something and my axle was sitting crooked. my thrust angle specified range is -0.15* to 0.15* and my before angle was
-0.42* and now its at -0.40*. could that be caused by lift or degre shims? if it was why didnt any body say something about it on the previous alignments? i didnt know you could align an axle on leaf springs. they said to fix it take it to a body shop or something. any body know whats goin on with my rear axle

thanks

Thrust angle: does it mean pinion angle?

MaXJohnson · Mar 6, 2006

little red cheroke said:
this is starting to wear my tires and its killing my gas mileage.

i got an alignment today and they said my rear end was out. they said my jeep had been wrecked or something and my axle was sitting crooked. my thrust angle specified range is -0.15* to 0.15* and my before angle was
-0.42* and now its at -0.40*. could that be caused by lift or degre shims? if it was why didnt any body say something about it on the previous alignments? i didnt know you could align an axle on leaf springs. they said to fix it take it to a body shop or something. any body know whats goin on with my rear axle

It could be caused by a shim if you didn't make sure the centering pin on the leaf was seated correctly. If the rear height isn't even from side to side, this could also cause a change in the thrust angle. Their guess of previous body damage could also be the problem. Not all alignment shops check thrust angle, and if they do, they don't always include it in the customer information sheet.

FWIW, it's not likely that this is "killing" your gas mileage. What is the wear pattern on your tires?

bretto · Mar 6, 2006

Kejtar said:
Thrust angle: does it mean pinion angle?

No, he is talking about the axle being twisted under the body making the wheelbases different from left to right. I have no idea how that could be adjusted though.
Brett

Kejtar · Mar 6, 2006

bretto said:
No, he is talking about the axle being twisted under the body making the wheelbases different from left to right. I have no idea how that could be adjusted though.
Brett

Ahh... I wonder if one extremely sagged leaf would not cause that as when flattening it shifts the axle back.

Timber · Mar 6, 2006

I believe GoJeep has stated on his website that the left side's wheelbase is shorter by 10 m.m. to compensate for crowned roads. IIRC.

Kejtar · Mar 6, 2006

Timber said:
I believe GoJeep has stated on his website that the left side's wheelbase is shorter by 10 m.m. to compensate for crowned roads. IIRC.

Umm that sounds like BS... cause that would mean that they would have to have a right and left hand drive versions.

Timber · Mar 6, 2006

I'm not saying it's true, but IIRC, he mentioned something like that on his site and that his left (American driver's) side was shorter as well.
EDIT: I guess I should look into it in case it's SPOBI, but the only idea/info. of his I can ever recall questioning was the t-case spacer thing. I think the reasoning there was a bit goofy.

little red cheroke · Mar 6, 2006

MaXJohnson said:
It could be caused by a shim if you didn't make sure the centering pin on the leaf was seated correctly. If the rear height isn't even from side to side, this could also cause a change in the thrust angle. Their guess of previous body damage could also be the problem. Not all alignment shops check thrust angle, and if they do, they don't always include it in the customer information sheet.

FWIW, it's not likely that this is "killing" your gas mileage. What is the wear pattern on your tires?

i have skyjacker 3" full leaf packs in the rear with built in shims. is it possiable that the center pin could have broken or gotten knocked out of the hole? i did the lift myself and i know the center pin was in correct. i didnt mean to say that its wearing my tires i ment to say that the alignment shop said it would start to cause tire wear.

bretto said:
No, he is talking about the axle being twisted under the body making the wheelbases different from left to right. I have no idea how that could be adjusted though.
Brett

thats exactly what the shop said. "rear end is out - twisted could not align" they said to take it to a body shop. but there dose not appear to be any damage to the "frame rails" or any thing like that.

Kejtar said:
Ahh... I wonder if one extremely sagged leaf would not cause that as when flattening it shifts the axle back.

my suspension is less than a year old and i dont cary much in the rear except when on the trails. could it be possiable that i broke a spring clamp?

Kejtar · Mar 6, 2006

little red cheroke said:
imy suspension is less than a year old and i dont cary much in the rear except when on the trails. could it be possiable that i broke a spring clamp?

spring clamps have nothing to do with sagging

little red cheroke · Mar 6, 2006

what exactly is thrust angle??

Wayne Sihler · Mar 7, 2006

little red cheroke said:
what exactly is thrust angle??

Don,t know ,But if thats what they call one side of the wheel base being longer or shorter than the other,maybe thats it.
There is room to move the axle on the springs as the center pin and the hole in the spring perch are not exactly the same size.We,re only talking a few thousants(sp). A good front end shop should be able to get a device that fits between the axle and spring that will slide,enabling the axle to be centered and then locked down,It,s a two piece affair that locks together when the U-bolts are tightened.
Wayne

Eagle · Mar 7, 2006

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=4

http://www.familycar.com/alignment.htm#Thrust Angle

rear end thrust angle

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