Decel vibrations on used truck - keep truck or not?

I would replace both front and rear brakes with oem. New pads, rotors, drums and shoes. It doesn't sound like a driveshaft issue, but just looking at that or the brakes for that matter isn't going to identify an issue necessarily.

A machine shop should be able to measure the driveshaft for run out.

 

Welcome to TW…mines done it since it was new.

 

Mine doesn't vibrate like that but you now have the opportunity to win somebody's farm if they are wrong in their diagnosis.
p.s - i would ask for pictures of the farm before taking the bet.

 

Hi , I just bought a 19 Sport with 60k. It did exactly the same thing , shudder / vibration below 30km. Even without brakes slowing down I could feel it. The truck had a 2” level kit and 1.5 block in rear. Also a diff drop kit. I took the lift out and diff drop out and the vibration is completely gone. My guess it is the drive shaft angles. If you like the truck, get them to put an axle shim on the rear and see if that helps

 

How many acres is your farm?

 

The truck is completely stock. I was considering shims but am concerned it may affect the angles elsewhere and either cause a new problem, or shift the current problem elsewhere. My concern may / may not be valid.

 

shims not a good idea if you are stock. fix it right. your concern is valid. (btw: lift etc makes you ineligible for that TSB).
just a little info on what is going on (assuming you do the coast test etc and it checks out). it sounds exactly like you have the following problem. some tacomas have it worse than others. on some it is intolerable and why TSB exists.

the 2 piece rear driveshaft is supported by a carrier bearing mid way. it is a bearing surrounded by a hard rubber donut. the front 1/2 of the shaft does not change in angle unless engine moves and is accounted for with universals. that is not the problem.
the rear 1/2 of the shaft moves due to "axle wrap" when decelerating. the universals have a limit spec. that is what they are looking for in the angle measurements...but with the axle wrap (due to weak springs) they shift to out of spec during deceleration, due to the reorientation of the driveshaft, which causes vibration and it is picked up by the carrier bearing and transmitted to the frame and that is why you feel it in the floor and seat and steering wheel etc.

replacing the stock leaf springs with off road leaf springs, which are stronger, prevents this pronounced axle wrap and eliminates the vibrations.
with a two piece driveshaft you will never get 100% rid of the vibrations since this is real life, which is why there is a donut on the carrier bearing. but the vibes should be minor if the leaf springs are preventing the pronounced axle wrap.

i can actually just barely detect the vibes (having had the TSB done) but i would never notice it if i had not been subjected to the massive vibes before the TSB...so i know what to look for. Now, anyone would say there are no deceleration vibes.
lol sorry got long.

edit: with new stronger leaf springs you will have different angles to be measured.
iirc there is a set of angle measurements for the non off road springs and for the off road springs. i was given a report of the angles before and after the tsb, and i hesitated because the after angles appeared to be out of spec...but i was wrong...different specs for different springs...they were in spec for the new springs.

note: axle wrap happens on acceleration too but in the opposite direction. apparently this is not a problem for non-lifted. all the complaints i have seen for stock seem to be related to deceleration and that is what the TSB addresses.

ugh: haven't really thought about this stuff in a while.
every system has a resonant frequency and that (and its harmonics) are what something will vibrate at. the body, frame, bearing, etc. are a system and obviously the rotational frequency of the driveshaft matches its resonant frequency somewhere between 30 and 10mph. if there is a small vibration, the carrier bearing rubber may damp it out but if it is large enough, the whole frame etc. system will be excited to vibrate. that is the explanation for this really only occurring between 30 and 10mph, me thinks.

 

How much of a difference in ride quality with the off road springs on a SR V6 4WD?
During test drives I drove a few off road new and used trucks and also standard SR access cabs in 2023 before purchase and some of the off road seemed a little floaty like on the highway and another one not much different than the SR. Tires are part of the equation and my SR like most has the Firestone Destination LE2 though some of the ones I drove had the LE3. This SR rides better especially over most bumps than my 2009 base access cab 4cyl did. I did read where with the stock springs people have reported the leaf springs sagging over time. I have the same style Leer 180 I had on the 2009 and that never had a problem with that.

 

the only difference i noticed between the stock and off road springs for my stock SR5 is the ride was a little stiffer.
i noticed it immediately but now i fogot all about it. it is what you would expect with stronger leaf springs.
it sounds like you have much more experience with comparing rides, i can only comment on what happened to my sr5. btw: still original tires - i am low use. i'd have to go out and read the brand - i don't pay attention to it much.

 

I got this going on. Seems like it just started recently.

Good info.

 

So is the ride height now higher in the back? if so how much? I'm guessing the spring swap does not change the resting angles, only prevents the spring base flexing on deceleration. I only have 1 month left on the 3 year part of the warranty. Got screwed out of a 3 days warranty which somehow started on the day the dealer got the truck, not the day I actually purchased it. Don't know if this would be covered under the drive train warranty with the TSB or not.

 

Mine had this when I first bought it (2016) and I recall I wasn't the only person noticing this on the 3rd gens. It never got better but after about 6 months I got a fiberglass topper and it instantly went away. Probably compressed the rear springs a bit and changed the angles. Wasn't this also a thing on 2nd gens?

 

i doubt leaf springs are considered driveline. they are suspension and the TSB is covered by basic 3yr/36K warranty. it is stated in tsb.
https://static.nhtsa.gov/odi/tsbs/2020/MC-10187246-9999.pdf
The warranty should be locked in when you present it with the problem, not when the work is done or finished.
if you have a month, get it there and acknowledged before it runs out.
i did not notice any different height with new springs but i would not be surprised if there was some, though maybe not. i was so happy it did not vibrate anymore and could care less about a small difference in height, if any. and you'll notice left and right side will measure different heights by about 1/2" to 1" due to "taco lean" so any difference, if there is any, is really in the noise.

 

yes, loading the bed does make the problem less severe, or disappear if it was minor. i noticed the difference with my hard/heavy tonneau cover but it still was significant. when i was ready to deal with the dealer/toyota re the tsb, i removed all loading from the bed so they could experience it, in all its glory, as delivered by the factory. a mechanic rode with me in the unloaded condition and immediately declared it a problem. he had seen it before, i think. vastly different experience from when i explained it to useless customer service people.
when it was all over, the service manager told me, next time, talk to the shop rather than customer service. good luck with that.

 

just a reminder that OP has not yet confirmed the leaf springs are the problem, though it is what has been talked about lately. I think it is the problem from my experience, but that is a sight unseen internet diagnosis. good info to suggest to the dealership for him though.

 

Just realized that it's my maintenance warranty that is almost up. One more year for the basic 3/36 warranty.

 

In my case, the dealer added 400+ lbs to the bed and said it decreased the vibrations but they were still there.

 

Definitely a driveshaft angle problem then. Most likely it’s too high. You can shim the center u joint and it will probably fix it. That’s standard practice after a lift, but it’s weird that a stock truck would need it

 

adding weight to my bed reduced it but did not eliminate it so i may have been same as @TacomaForNow.
ridiculous it can go out the factory this way.
as far as shims: here is my ruminating.
i was considering shims too until found the tsb and fought for it.
i'll use "kink" and CW/CCW rather than +/- angles to keep this simple (for me to write ).
assuming axle wrap due to weak springs is the problem... if you look at the kink of the driveshaft at the carrier bearing, it is towards the top of the truck. when accelerating, and observing from the driver side, the differential rotates CW. which means it goes thru the straight condition to the opposite kinked condition. just the reverse with the deceleration ie CCW but it does not have the benefit of rotating thru the straight condition.
i think the acceleration wrap is more severe and toyota dealt with it in this way. but that left the deceleration wrap a secondary issue. it is a lot easier for the deceleration axle wrap to become a problem.
if you straighten the kink, you will likely start having acceleration axle wrap problems at the expense of improving the deceleration axle wrap problem. maybe you will get away with it, maybe you won't and you'll have acceleration vibrations.
just what i think is going on. i never tried shims to test it out.
heftier leaf springs reduces the differential rotation both CW and CCW and makes it easier to eliminate the vibrations.
edit: regardless of the kink, the universal at the differential is getting beat on too and that may be the most vulnerable point. thinking "straight" from the perspective of the differential universal is probably most valuable.
i know, lets draw free body diagrams and analyze the forces and angles. lol like engineers did a decade or more ago when designing it. all this is not really of interest to OP if leaf springs is the solution. (it is).
or it's the torque converter