Bucking from rear end of DCLB?

I used to own a 99 AC 4x2 OR and traded it in on a 16 DCLB 4x4 OR. Since almost day one, I have noticed a bounce from the rear end of the truck that seems unusual to me and feels different than anything from my old truck. It is hard to describe, but the best I can do is say it feels like the truck is trying to buck me off. It feels like an exaggerated bounce from the rear end that pitches me forward. Seems to happen at multiple different speeds, but it usually while under light load steady speed driving 30+mph or when decelerating slightly.

I first noticed it while driving with my wife beside me, and she was holding a fast food cup in her hand and the bucking kept rattling the ice in her cup. At first I thought she was doing it intentionally and asked her to stop, as it was annoying me. That is when she told me she wasn't doing it...it was the bouncing from the truck. Since then, it seems to come and go and be worse at some times than others. It is bad enough that it bothers me at times...kind of feels like the truck is trying to rattle my brain around by bouncing it against the head rest. The tires and suspension are stock, dealer had inflated the tires to 37 front and 36 rear. I dropped them to 35 and 34 just to see if it made any difference...it didn't.

What I can't figure out is if it is just excess bounce in the rear suspension that is totally normal for a DCLB truck with an OR suspension...or if it is something in the drivetrain that is causing a hitch or bounce from the rear end. I do hear a light whine when cruising at about 55 mph that is RPM related, not tire or wind (the sound goes away almost immediately if I let off the gas and the RPMs drop, instead of slowly going away as the speed goes down), but I don't really think it is necessarily related to the bouncing issue. Would low fluid in the rear differential have the potential to cause this kind of issue? I have greased my U-joints, and all the zerks took 6-10 pumps to start purging.

Anybody else have the same sensation or issue and have any insights on whether it is normal or something to take to the dealer? I know the dealer's first gambit will be that it is totally normal and just how the truck is supposed to drive, so I want to be a bit more educated about what I am feeling before taking it in.

 

I think I feel it too. Is it like a wave or push when slowing down? Like the truck pushes you forward.

 

Not in my case. This is like the rear end has stiff springs and no shocks to damp the bounce. It is like driving through a set of very small parking lot speed bumps, but only the rear end is hitting the bumps. The truck just feels like the rear end is kicking up harder than I would expect, repeatedly. The weird part is that when I hit actual bumps, the rear end doesn't feel that stiff...it is actually quite smooth over real bumps. That is the part that makes me wonder if it is drivetrain related instead of suspension.

 

Does any of your local dealer have a OR LB for you to test drive to compare?

 

LOL...GST doesn't even want to admit that the DCLB exists (had at least 2 of their sales people tell me the Tacoma wasn't made in a DCLB configuration), much less stock any for sale at their dealerships. I had to fight to get mine ordered and then wait 4 months to receive it. Maybe I can find one up in Albuquerque to try when I go through there next week for work. Good idea!

 

Make sense.

Just like my local salesman argued with me, that Tacoma doesn't come in a real man 3 pedal model. When I showed them it does, they told me as a woman why would I want a manly 3 pedal. When that didn't work, they tried, why would I order a Tacoma, it isn't a Ferrari and doesn't necessitate an order....

 

Sounds like the sales folks don't change much by region...

 

How long did you drive/own the AC? the DCLB should and will drive significantly different than your old AC because you have much more chassis behind you. With no weight on the bed, it will feel 'empty' so to speak.

I'm not saying there are no real problems, but I find if you're used to one vehicle's characteristic, driving something different will have a very different feel that may be good or bad.

Go drive a DCSB if your dealer doesn't have a LB and compare. Should feel very similar/same as your truck, and you'll know for sure if there are any problems with your truck. The rear solid axle with leaf springs is really old technology and works fine. The only issue I think you could have would be that the shocks are not damping correctly. Again, that's pretty easy for a dealer to diagnose, but you should for sure drive a DCSB and compare with your truck.

 

I drove the 99 ACLB for 17 years and ~205k miles. That is what I am wondering...is this just a function of the longer chassis or the difference between 2wd and 4wd weight that I will eventually get used to or is it a real issue I need to see the dealer about? I don't think it is a lack of damping issue because when I drive it off road or over bumpy roads, the suspension feels fine and there is no excess bounce beyond what I would expect. It is certainly smoother than my 99 over similar roads and bumps. The fact that this bucking seems most noticeable on mostly flat relatively smooth roads is what makes me wonder if it is something else.

 

The DCLB places you significantly more forward from the rear axle compared to your '99 AC. Remember, this is a bigger truck altogether.

I want to say it's something you probably aren't used to. But again, I would go test drive a DCSB if your dealer doesn't have a LB to compare. If it feels the same, then it's just a characteristic of the truck you're not used to. If it drives completely different, then there maybe some damping issues with your truck. Remember, shocks react different to high speed and low speed damping. High speed is sudden jolts (like if you go off road or go over a speedbump quickly) and low speed damping is smooth non sudden bumps. Just because a shock does well at high speed damping doesn't mean it is working in low speed. A good shop should have a shock/strut dyno to check this.

 

Thanks! Good point about the difference in damping speeds. I was mainly fixated on whether it was just the longer chassis, but will try a DCSB just to see how it feels. I drove one for a test drive before placing my order, but don't remember noticing the bounciness then. But I was thinking about so many different things during the test drive, I could have just not noticed it.

 

I get the same characteristic as yours. Mine is a Sport
but I do feel like the suspension was truly tuned with
some load on it.

I hauled trash, 700 lbs once on the back of this thing.
It was a day/night difference. The truck felt settled in
and smooth. I had my dad drive it too and he agreed.
It behaves better at the bump with a load.

Try loading some sand bags in the back. Maybe
200 lbs. If your truck stops behaving that way, then
it is going to be the suspension.

 

Are you on paved highways or cement? If you are on cement it's due to how much space is in between each slab of cement. We have that here in California and I have felt it with my last two trucks as well.

 

On the I-15 between Temecula and San Diego there's a cement part that really makes the truck jump.

 

Shit is all over the 5, 55, and 405 in my area or Orange. My Tundra used to be a bucking bronco. Tacoma, not so much as the Tundra but having the DCLB is basically the same lenth.

 

I have noticed it on both concrete and asphalt. It is not the same feeling as just bumping over the expansion joints in concrete. This is more movement and less of a sharp sensation. It may still be the way the longer chassis handles natural harmonics generated by the undulations of the paved surfaces, but it is different than the 'thump thump' of going over expansion joints in concrete paving like you get on older highways.

I remember driving a Ryder truck up through Arkansas one time and Hwy 59 between Texarkana and Little Rock was absolutely TERRIBLE concrete. The sections were uneven, and the length of the slabs and angle that they met at was just right to set that Ryder truck bouncing like crazy at any speed between about 50 and 65 (during the 55 mph speed limit era). Worst couple of hours of driving I can ever remember...

 

Also make sure you are running the correct tire pressure stated in the door placard. Just a couple extra pounds of air will exaggerate that bronco with an empty bed. Remember, 32psi cold will be 35psi hot!
First day I drove mine on a longer drive highway(between San Diego and Temecula) she bucked like hell. Checked the tires and lowered to 30 cold(TRD Sport 4x2 w/the Toyo's). Reduced the bucking quite a bit.

 

Is tire pressure not always measured cold? Of you go to door jamb specs after a long drive, you're underfilling your tires.

 

Well it should be but some peoples kids.........

 

Dont forget the 91, not sure if they have done any maintenance on it, through Corona....