97 LX450 Squeal in Reverse

[jonheld]

I did some searching on this issue and it seems to be common with the A343F transmissions.

I was nose down in a field and started to reverse out. There was a horrible squeal from the transmission as I increased throttle, so I immediately backed off. Dropped her into low range and there was no issue backing out.
I have never heard anything like this from an A440F.
This truck gets yearly fluid changes using all Amsoil products. She runs strong, cool, and smooth.

In any case, my searching has yielded "that's the way it is", similar to the 91/92 driveline clunk. I will say that the sound made me sick to my stomach. It can't possibly be a good thing.

 

[ccslider]

I heard that before and researched to try and figure it out.

Some said the viscous coupler in transfer case, dry spindles, drive plate worn, tsb updates to transmission valve body.

It's only happened twice. Both times the driveline was loaded pretty well.

I'm about to go part time so I was going to check it out then.

 

[mingles]

Has happened a few times (3-4) on my '97 LX in the last 70K miles. A few observations...

• has only happened in hot summer weather, never winter
  
• seems to be correlated to "goosing" the throttle in reverse or accelerating too quickly after a shift into R. Slow and easy application is fine.
• not related to VC in my case. My truck has it removed.
• agreed, it is a horrible noise

 

[Tools R Us]

I did some searching on this issue and it seems to be common with the A343F transmissions.
...

It's rare, only seem it on a limited range of '97 production. The TSB indicates check balls in the valve body. On one, a known good valve body from a '96 was swapped, the problem didn't change, swapping the whole trans solved it.

 

[decoco]

Has happened a few times (3-4) on my '97 LX in the last 70K miles. A few observations...

• has only happened in hot summer weather, never winter
  
• seems to be correlated to "goosing" the throttle in reverse or accelerating too quickly after a shift into R. Slow and easy application is fine.
• not related to VC in my case. My truck has it removed.
• agreed, it is a horrible noise

Similar experience, I have had it happen a bit more lets say about 7 times in 40,000 miles.
And it does seem to be related to "goosing" the throttle or accelerating too quickly after a shift into R.

I wonder if there's any real reason to try to solve this occasional squel or leave as is.

 

[mingles]

I wonder if there's any real reason to try to solve this occasional squel or leave as is.

On my list of challenges in life, it’s pretty far down the list .

 

[cahill]

I have had the same thing happen a few times when backing up a tent trailer up my slightly sloped driveway in my 97 LC. Had it happen too with my 97LX450. Sometimes it does seem to be when applying gas too quickly after shifting into reverse, at other times it seems to be the load and switching to 4L helps. Not sure what to make of it, but sure would prefer it not to happen.

 

[decoco]

does it have to do with the weaker reverse gears in the 80? I thought I read somewhere that the gears in the 80 were machined in a way where they are stronger for forward use but it's a weaker gear in reverse- or something like that- I clearly do not remember this comment very well.

 

[OGBeno]

does it have to do with the weaker reverse gears in the 80? I thought I read somewhere that the gears in the 80 were machined in a way where they are stronger for forward use but it's a weaker gear in reverse- or something like that- I clearly do not
remember this comment very well.

that’s for the front diff.

 

[scottryana]

My $0.02. As the transmission wears the clutches and steels wear and don't develop the same clamping force they did before. There are 3 line pressure settings in the transmission. I would drop the pan and click it over to the next higher setting....

 

[cahill]

My $0.02. As the transmission wears the clutches and steels wear and don't develop the same clamping force they did before. There are 3 line pressure settings in the transmission. I would drop the pan and click it over to the next higher setting....

But why then would it show up in reverse only and not in drive? You'll have to pardon my ignorance - I don't have a good understanding of transmissions.

 

[scottryana]

It is completely possible the hydraulic pressure is lower in reverse than forward. It is really hard to say. I have not seen any hydraulic pressures listed for the Toyota transmissions but reverse can be higher or lower pressure in domestic transmissions depending on the valve bodies.

The other thing is that most transmissions rate line pressure at 2000rpms, and most people aren't reversing at 2000rpms.

But why then would it show up in reverse only and not in drive? You'll have to pardon my ignorance - I don't have a good understanding of transmissions.

 

[jonheld]

My $0.02. As the transmission wears the clutches and steels wear and don't develop the same clamping force they did before. There are 3 line pressure settings in the transmission. I would drop the pan and click it over to the next higher setting....

What effect does that have on overall "driveability" of the vehicle on and off road?

 

[jfz80]

Lots of reports of folks plenty happy with upping the line pressure by clicking over to the next setting in the pan. Effects similar to a mini shift kit with firmer crisper shifts due to upped pressure.

There are some older threads discussing small differences b/w the 343 models along the way showing a small window of jan-aug 97 to be most desireable from oe upgrades from tsbs along the way. Id link one but it just deleted this post when i went to look and i nonlonger have the window open.

I suffer the same squeal in reverse and it is very disheartening. for me, It does not matter whether accelerator use is shortly after shifting into reverse or not. Also mine is a 95 model and still suffers the same experience. As well mine has only happened in the cold, semi buried in snow, opposite of a few descriptions above

I suspect clutch wear at 320k

 

[scottryana]

Jon, I believe that it would help to restore the transmission to something closer to what it was like when it rolled off the show room floor. Automatic transmissions absolutely have wear items, just like the clutch of a manual transmission. Over time the clutch material and steels wear and the clamping load decreases this could take years and years if the transmission is well taken care of but these trucks are 20 years old so they certainly have made it to their designed lifespan I would imagine.

I think in an effort to make the later 80's and LX's more luxurious they softened the shifts basically the equivalent to "slipping the clutch" in a manual. Harder shift save the clutches but put more stress on hard parts.

So in short it might firm the shifts up some, but I don't think it would be much and should make overall drivability better.

What effect does that have on overall "driveability" of the vehicle on and off road?

 

[jonheld]

Jon, I believe that it would help to restore the transmission to something closer to what it was like when it rolled off the show room floor. Automatic transmissions absolutely have wear items, just like the clutch of a manual transmission. Over time the clutch material and steels wear and the clamping load decreases this could take years and years if the transmission is well taken care of but these trucks are 20 years old so they certainly have made it to their designed lifespan I would imagine.

I think in an effort to make the later 80's and LX's more luxurious they softened the shifts basically the equivalent to "slipping the clutch" in a manual. Harder shift save the clutches but put more stress on hard parts.

So in short it might firm the shifts up some, but I don't think it would be much and should make overall drivability better.

So would this be equivalent to slightly adjusting the kick down cable? I would much rather do that then drop the pan.

 

[scottryana]

I suppose, I don't know how much the kickdown cable contributes at low throttle inputs.

So would this be equivalent to slightly adjusting the kick down cable? I would much rather do that then drop the pan.