I applied Reese weight dist hitch and noticed that the 4runner didn't dip or drop at all at the front and rear. Is that ok?
You need to KNOW your tongue weight -- it's important. As [MENTION=113611]m85476585[/MENTION] said, it s/b ~7-10% of your trailer's weight.
Too little TW is not safe.
Using the same trailer of 3,980 lbs [510lb tongue weight] the 4runner dipped 2.5 inches in the rear and raised an inch in the front when i didn't use the weight dist hitch. the V8 4Runneer has 700 lb tongue weight capacity.There should be about 400lbs (10%) on the tongue before you hook it up. I would expect that to cause the suspension to dip some, more in the back than the front even with weight distribution.
Make sure the weight distributing bars have some tension, but not too much. I always set them so it only takes a moderate amount of force to latch the chains that pull on the weight distributing bars, but I'm not sure if that's correct. Since it can handle 4000lbs without weight distributing I would err on the side of less tension. Although you could get by without weight distribution it usually helps the load be more stable, and it allows you to add a sway control setup, which may be handy for a relatively light and short wheelbase tow vehicle like the 4runner.
Finally, make sure you either have a brake controller for electronic brakes (The V8 model is pre-wired for it, I think, but you still have to buy the brake controller separately), or make sure the trailer has hydraulic surge brakes and that they are adjusted correctly.
4k for a 20' trailer? Wow, that's heavy! Is it a vintage trailer or a toy hauler? I know some of the older trailers with wood frames were on the heavy side.
As for it not "dipping down" isn't that exactly what the WD hitch is supposed to do? I know I get a little bit of "droop" when I hook our little T@B up to my V6 and that thing only weighs maybe 1700 or so. Haven't measured the tongue weight, I'd guess it's between 150 and 200 which is what it should be.
The trailer has 500lb tongue weight and 4runner has 700lb tongue weight capacity.
Using the same trailer of 3,980 lbs [510lb tongue weight] the 4runner dipped 2.5 inches in the rear and raised an inch in the front when i didn't use the weight dist hitch. the V8 4Runneer has 700 lb tongue weight capacity.
OK, I don't want to get all fussy on you here, but judging by your use of the term "capacity", I'm suspecting you don't know what I mean by tongue weight. Sry if I'm telling you something you know, but this is important.
Check this out:
https://www.etrailer.com/faq-how-to-determine-trailer-tongue-weight.aspx
do you have the air suspension on your truck? it's possible the air suspension raised the rear end to compensate for the dip. Unlikely but anything is possible.