Aftermarket Rear Springs with Original AHC System? (1 Viewer)

[doober]

Yes, check pressures and gradations every year or two (or if you add/remove lots of weight) and you're good.

Had a quick follow-up after my AHC fixes. Recently I had new OEM trailing + control arms installed along with take-off Lexus OEM springs (only 39K miles on them). After checking pressures initially, i could very clearly tell my springs were shot so I replaced them with these. Since my mechanic did the work, I'm noticing significantly more sag on the driver's side rear than the passenger. Hub cap measurements indicate 20" on driver's rear, and 20 3/4" on passenger rear. My fronts are perfectly level about 1/16" above 19.5" so within a good +/- of spec.

I'm curious if my mechanic possibly installed the springs incorrectly and put the taller spring on the passenger side, therefore forcing the truck lower on the driver's side. I do not think it's an issue with the LR shock, the seap on it is equivalent to the RR. Do you have any thoughts beyond incorrect spring install as to what could be causing this?

Overall, the AHC system is in much better shape, I went from 7 graduations back up to 11 after new components and proper adjustments, so that's good news at least... But this difference in height in the rear is baffling me...

 

[IndroCruise]

Had a quick follow-up after my AHC fixes. Recently I had new OEM trailing + control arms installed along with take-off Lexus OEM springs (only 39K miles on them). After checking pressures initially, i could very clearly tell my springs were shot so I replaced them with these. Since my mechanic did the work, I'm noticing significantly more sag on the driver's side rear than the passenger. Hub cap measurements indicate 20" on driver's rear, and 20 3/4" on passenger rear. My fronts are perfectly level about 1/16" above 19.5" so within a good +/- of spec.

I'm curious if my mechanic possibly installed the springs incorrectly and put the taller spring on the passenger side, therefore forcing the truck lower on the driver's side. I do not think it's an issue with the LR shock, the seap on it is equivalent to the RR. Do you have any thoughts beyond incorrect spring install as to what could be causing this?

Overall, the AHC system is in much better shape, I went from 7 graduations back up to 11 after new components and proper adjustments, so that's good news at least... But this difference in height in the rear is baffling me...

I wrote some rambling notes on a similar question -- can be found posted here -- these may give you some ideas.

 

[doober]

I wrote some rambling notes on a similar question -- can be found posted here -- these may give you some ideas.

Thanks for this, that was a great write up. Given the fact I wasn't experience this discrepancy in the rear prior to the springs being installed, I am going to check the spring seats first, and ensure the right spring was installed in the right spot. I will note that the LR was a bit lower than the RR prior to the work being done, however it was certainly within spec, only about 1/8" lower, not 0.5" out of spec like it is now. I like your idea of measuring from frame lift points. I feel as though this would give a solid indication if a shock bushing or if there's an issue with other mechanical components.

On a simpler note, I noticed that the Lexus AHC springs have a color coded sticker on them, one is yellow one is green. My springs are compressed now, so I can't tell which is which. Do you happen to know which color pertains to the longer spring meant for the drivers side of the truck?

 

[IndroCruise]

Thanks for this, that was a great write up. Given the fact I wasn't experience this discrepancy in the rear prior to the springs being installed, I am going to check the spring seats first, and ensure the right spring was installed in the right spot. I will note that the LR was a bit lower than the RR prior to the work being done, however it was certainly within spec, only about 1/8" lower, not 0.5" out of spec like it is now. I like your idea of measuring from frame lift points. I feel as though this would give a solid indication if a shock bushing or if there's an issue with other mechanical components.

On a simpler note, I noticed that the Lexus AHC springs have a color coded sticker on them, one is yellow one is green. My springs are compressed now, so I can't tell which is which. Do you happen to know which color pertains to the longer spring meant for the drivers side of the truck?

This Post #184 by @Hulio at Page 10 of a long thread probably gives the most direct and relevant answer.

There is considerable background which is summarised by @uHu at Post #74 at Page 4 in the same thread.

My own notes may be of assistance at Post #165 at Page 9 of the same thread. This leads eventually to the abovementioned Post #184 by @Hulio

 

[doober]

This Post #184 by @Hulio at Page 10 of a long thread probably gives the most direct and relevant answer.

There is considerable background which is summarised by @uHu at Post #74 at Page 4 in the same thread.

My own notes may be of assistance at Post #165 at Page 9 of the same thread. This leads eventually to the abovementioned Post #184 by @Hulio

Thank you, can confirm then that the taller spring is on the passenger side. I will start my diagnosis by switching them.

 

[LVALL029]

The progression is roughly like; AHC, spacer, King, king with spacer, lx450, non-AHC 100 spring. Notice how there's no dobinsons or ARB on that list?

Check pressures first and follow along with my YouTube guide and cheat sheet. Google YotaMD AHC.

Please add this section to your YouTube video!!! That’s been my guide to tune my AHC… already changed the fluid, adjusted the cross sectional heights, adjusted torsion bars and added 30mm springs but my rear pressure is still at 7.3… king springs are the next step!