Coil springs for AHC (3 Viewers)

[trdcorolla]

Did you notice a ride quality difference with the new springs?

Not really. The ride quality came back when I replaced the 4 globes. I had 5 grads during my test (7 is minimum/end of life) and my AHC pressures were all in spec with those 5 grads. I would put in a 30mm spacer and go from there before replacing the coils.

 

[ylexot]

I replaced my tired LX couls with new AHC LC coils and added a spacer to get back into pressure range a few years ago. Biggest benefit from springs is taking load off of the hydraulics. Before the LX was having a hard time holding up its end of a popup camper. The system worked much better with fresh springs.

Ride quality is mostly about the globes, fluid, and bushings.

 

[swoop]

I replaced my tired LX couls with new AHC LC coils and added a spacer to get back into pressure range a few years ago. Biggest benefit from springs is taking load off of the hydraulics. Before the LX was having a hard time holding up its end of a popup camper. The system worked much better with fresh springs.

Ride quality is mostly about the globes, fluid, and bushings.

Any idea on when coils should be replaced? My 05 is still on its original coils as far as I know.

 

[swoop]

it almost sounds to me like it’s not worth replacing springs, just put a spacer on them and call it a day? Or would fresh springs alone help bring pressures into spec at all

 

[uHu]

Is there a definitive agreement on when coil springs should be replaced? And would one expect new coil springs to raise the neutral height of a ahc equipped vehicle with worn out springs? Or would ahc just compensate, and pressure would fall in spec.

Also, correct oem part numbers for a lx470 rear spring replacement would be:
RH: 48231-6A730
LH: 48231-6A740

Correct?

it almost sounds to me like it’s not worth replacing springs, just put a spacer on them and call it a day? Or would fresh springs alone help bring pressures into spec at all

Absolutely worth it to change coils. Change whenever the pressure goes above spec (after approx 5 years). And yes, the state of the springs affects the ahc pressure, not the height (as long as it can cope with the weight).
Get the brown dot springs, 48231-6A780 if you don't have too much armour, drawers or other permanent extra weight. They are the strongest OE ahc springs for the 100.

 

[ylexot]

I'll concur with Uhu on the 5 year lifespan. My springs are getting to be about that old and have have been well used and I plan for fresh springs in not too distant future. Thanks for the tip on brown dots.

 

[katit]

Get the brown dot springs, 48231-6A780 if you don't have too much armour, drawers or other permanent extra weight. They are the strongest OE ahc springs for the 100.

Do you suggest those for both sides (L and R)?

 

[swoop]

Absolutely worth it to change coils. Change whenever the pressure goes above spec (after approx 5 years). And yes, the state of the springs affects the ahc pressure, not the height (as long as it can cope with the weight).
Get the brown dot springs, 48231-6A780 if you don't have too much armour, drawers or other permanent extra weight. They are the strongest OE ahc springs for the 100.

Are those the same as part numbers: 48231-6A730 & 48231-6A740? I believe I recall something to the extend of the Lexus springs being longer and the Toyota ahc springs having a stiffer spring rate. I am looking for ones that would provide the softest ride possible, and don’t have much permanent rear weight besides an occasional tow under 3,000 lbs.

Side note but does anybody else have issues with being able to see where the Ahc fluid lies in the reservoir? I can’t see into the reservoir to count gradations from L to H.

 

[uHu]

Different part numbers are not the same parts. The brown dot springs give the ahc a lower pressure, making it easier to carry a bit of load and giving the globes an easier life.
You can get 48231-6A730, 48231-6A740, 48231-6A750 (H=455mm, pink), 48231-6A770 H=485mm, purple) or 48231-6A780 (H=500mm, brown). All will fit, but having slightly different lengths and/or rates. You can have 2 different ones with the longer/stiffer on the left, to help the TBs balancing the truck, or just leave the extra weight on the left to the TBs. Both methods are used.
I guess it comes down to what you can get hold of, as some might be out of stock, I've heard.

 

[namsag]

I have read the big AHC thread a few times through and I think I have a pretty good handle on the subject, except the part about the coil spacers. I am getting ready to replace my rear coils with oem AHC coils (2005 LX). The point I don't fully understand is where the spacers come in. So, the spacers will raise the height, OK. I'm not actually looking to raise the height, only to lower the AHC pressures. So then with spacers the rear end is 30mm higher, does this mean the rear height sensor has to be adjusted to get the rear height back to stock spec?

 

[uHu]

I have read the big AHC thread a few times through and I think I have a pretty good handle on the subject, except the part about the coil spacers. I am getting ready to replace my rear coils with oem AHC coils (2005 LX). The point I don't fully understand is where the spacers come in. So, the spacers will raise the height, OK. I'm not actually looking to raise the height, only to lower the AHC pressures. So then with spacers the rear end is 30mm higher, does this mean the rear height sensor has to be adjusted to get the rear height back to stock spec?

Go do your homework over again.
Changing the springs or adding spacers will only change the pressure, not the height (how could it?) as long as you stay within the scope/specs of the ahc. Only the sensors set the height. You can change the pressure by either changing (or adjusting) the springs or by changing the height.
Spacers are for helping springs if they are sagging, too short, or you can't get longer ones. If the springs are old and sagging, it's better to replace than to add spacers.

 

[namsag]

Well, everyone keeps talking about getting new coils AND adding the spacers. The point seems to be that the new springs will improve pressure, and the spacers help as well. My question is how to manage the height.

In my only previous experience with spacers, they absolutely DO raise the height. If you take a spring of any length and add length to it, how can it NOT be longer (higher)? Let's see, springs + more "space", how can it not raise height? I put 30mm coil spacers all around on my G-Wagen, the same way they would install on the Cruisers, and imagine this, the whole vehicle sits higher now. Must be that Common Core math.

Of course, the G does not have active height control, and so that is the source of my uncertainty. Perhaps I asked the question poorly. Will the AHC and the sensors compensate for the lift provided by the 30mm of spacer or does the "space" need to be compensated for manually by adjusting the rear height sensor?

 

[swoop]

The ahc will compensate is my understanding. And will lower to adjust for that extra 30 mm of spacing. The net result will be that ahc pressure will be less than if you had only just swapped in new springs, theoretically reducing wear and tear on ahc components above and beyond what just springs would have done. I believe it also would help the weight limit capacity before bottoming the system out.

 

[swoop]

On the topic, does anybody get a clunk whenever the ahc adjusts itself in the neutral setting? Lots of times in the morning when I first turn the car on it will level itself. Right at the end of the leveling, I’ll get a clunk as it settles into the final position. Is this normal?

 

[katit]

Of course, the G does not have active height control, and so that is the source of my uncertainty. Perhaps I asked the question poorly. Will the AHC and the sensors compensate for the lift provided by the 30mm of spacer or does the "space" need to be compensated for manually by adjusting the rear height sensor?

AHC looks at height sensor and adds pressure as needed to get truck to the proper height. Springs just helping. Once they compress - AHC pump have to work harder (higher pressure). Adding spacer just compensates for worn spring bringing pressure down and close to specs. But as you understand spring ratio will change and globes will not provide exact same dampening effect.

Springs - wise it seems that Lexus uses 48231-6A740 on left and 48231-6A730 on right.
LC uses x780 and x770. I just placed an order for 2 of those as Lexus springs were considerably more expensive and LC springs will buy more time by taking away from comfort. But if I plan to tow/etc LC springs will be better. And should last longer

 

[katit]

On the topic, does anybody get a clunk whenever the ahc adjusts itself in the neutral setting? Lots of times in the morning when I first turn the car on it will level itself. Right at the end of the leveling, I’ll get a clunk as it settles into the final position. Is this normal?

I don't think it's a clunk. I hear 2 sounds, first when pump runs and stops (not lout at all, hear it when HVAC off and engine idles)
Second sound comes from a back. I would think it's a solenoid cuts off when pressure reached, I guess this is what you hear.

 

[namsag]

Thank you @swoop and @katit.

I have heard the clunk once or twice when moving my AHC, no idea what it is, I have only had the vehicle a few months, have heard it two or three times. My system is flushed, pressures a little high, that will soon be rectified.

 

[BEG]

On the topic, does anybody get a clunk whenever the ahc adjusts itself in the neutral setting? Lots of times in the morning when I first turn the car on it will level itself. Right at the end of the leveling, I’ll get a clunk as it settles into the final position. Is this normal?

You will hear the pump run as it moves the suspension into position. A few seconds after the correct height is reached, you will hear another sound when the accumulator finishes pressurizing.

 

[ylexot]

I have heard the clunking sound when adjusting height. I've assumed it was springs adjusting to new position and load. If that is all it is, I doubt it is a problem.

 

[DJCloz]

I just skimmed through the thread and am looking for some clarity, with the king coils in the rear, is the AHC still able to drop down to the L position? my AHC struggles when I have people in the 3rd row seats or excess gear. I am hoping replacing my tired 20 year old coils will fix this. I still need to be able to get in the low position to fit in my garage with a roof rack though.