1st Gear vibration cause?

I've seen it discussed before but not sure if the root cause has been determined.

The truck:
'13/2.7/4x4/Aisin 5sp manual/4.10 diffs/40k miles

Issue: First gear only shudder feeling in the drivetrain that becomes evident around 3500+ rpm. Throttle input doesn't seem to matter if part/full. In day to day driving this is a non issue, however when towing a loaded trailer I wind the 2.7 out much higher than normal, especially in hilly areas - and if I had to guess between 50-75% throttle. That said, even without a trailer I can replicate the shudder if I wind the motor out in 1st.

I don't think it's the clutch as it is fully engaged and I detect no slip either by feel or visual reference of the tachometer. I'm the 2nd owner, purchased at 34k miles. Now at just over 40k. Been driving stick shift 20 years and do not believe I am the problem either. The selling dealer replaced the clutch on their dime as I found it to slip on my test drive (lol at their "certified Toyota" checklist).

Who else has experienced this shudder feeling? Is it just a combination of the engine/trans harmonics? The perfect storm so to say. I can even see it in the shifter. I'm not too concerned by it, moreso curious.

 

Does it do it when you are in 4x4 in 1st gear taking off from a stop? Try it and report back.

 

Mine has done that for 86,000 miles now

 

Access cab / double cab? sounds like axle wrap to me. Like stated, put her in 4hi in a striaght line a from a stop take off good and i bet it doesnt vibrate.

 

It's an access cab. So by putting in 4hi I presume the theory is that since 50% of the power would go to the front, less load on the rear diff and the angle doesn't get as wild? I'll have to try it but I don't have a dirt road nearby.

I have

$105 hellwig 550 helper spring kit - 550

hellwig 550 helper springs that I'm planning on installing this weekend. I bought them to help the rear from sagging so much from the tongue weight on my trailer. Will they help axle wrap? Ive seen some say only if they're installed in front of the axle, but I really need them behind the axle to keep my nose down when loaded - it doesn't take much weight at all to bring the rear down.

 

You dont need a dirt road, just a straight paved road will do. Flip her in to 4hi before you come to a stop at a stop sign / stop light so its all the way in then take off good. before you have to make a turn just flip her back into 2hi.

Helper springs should help a little but its still a very soft leaf pack from the factory that allows all the axle wrap.

And being an access cab lb (same wheel base as the DCSB) you have the driveshaft setup that has the shortest rear section of driveshaft which makes any pinion angle changes much more pronounced. A regular cab has a one piece driveshaft which makes things much better as angle changes are not as compounding with its much longer driveshaft. And the DCLB has a 2 piece design like your truck but the shaft sections are longer as well for the longer wheelbase.

 

Search "take off shudder" in the forums

 

my 99 2.7 did it and so does my 2009 v6

less pedal on take off helps a lot if you don't want traction or ladder bars

 

@jmgtp Did you ever try what we said to diagnose the issue? What was the result?

 

Yes - just tried it this morning on my way to work. The short story is that - I agree that it was caused by axle wrap due to the super soft leaf pack.

The longer story-

In 4x4, from a stop and accelerating pretty quickly in 1st gear through 4500 rpm - no vibration.

When not in 4x4 it's much improved as well. I installed the helper leaf springs on Saturday. I can still feel it but it is diminished. Even with the half helper leafs installed the rear of the truck is still soft. I have some towing to do this weekend so I'll also be assessing if I need to add another set of helper leafs to the springs on the front side of the axle. It may be ok for my needs as is though.