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Discussion Starter #1
I'm at the end of my rope with this problem. I've searched forums high and low for over 2 years and can't seem to find any definitive answer on this.

I have a 99 Tacoma Xtra cab, all stock, no lift, that I have been plagued with a vibration with for a couple years now. There's 166k miles on the truck.

The vibration feels like it is in the driveline. It ONLY happens in 5th gear. The minute you go to 4th its gone. I've tried different pedal pressures and speeds and can't get it to occur in any other gear. The vibration is significant enough that it buzzes the whole cab, causing the dash to buzz and vibrate and my sunglasses on the dash to buzz against the windshield. The vibration generally goes away as I get up over 60 or heavy on the gas. But light pedal and 2k RPMS or less and it's buzz buzz buzz and shake shake.

I just finished having the whole driveline rebuilt by Driveline services of Portland. New OEM carrier bearing, new flange, new yoke, new U-joints and I honestly couldn't even find anything wrong with the driveshaft when I removed it. Looked perfect. Driveline services said the double cardagon (CV joint) was fine and spun it up to over 3000RPM and no vibration. However, while I had the driveshaft off I drove the truck around in 4 wheel drive and in 5th gear and no noise and no vibration.

I've read posts all over the web about this problem, people rebuilding drivelines and rear ends and still having the issue. At this point I am beginning to suspect that 5th gear may be the issue but of course that is a ton of work and I would love to have someone experienced with this issue chime in before I drop transfer case and transmission.
 

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Do you have the 2.7 or 3.4? I have a 99 with the 2.7 and I cant use 5th gear until about 55mph without lugging the engine which makes the whole cab buzz. 5th gear is an overdrive ratio and the engine has less mechanical advantage so it is easier to lug at low RPM. Sounds normal to me?
 

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Hmmm, well I do know the drivetrain will make much more vibrations in 5th at low RPM. If it didn't occur when new, maybe the trans and/or motor mounts have hardened up and are transferring more vibrations now? I could be wrong but I don't imagine it being an internal problem with the trans. That's all I got, maybe someone else will have a better idea
 

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Discussion Starter #5
I tried it out again this morning. 2k RPM in 5th with light throttle I get heavy vibration. 4th gear @ 2k RPM light throttle - butter smooth.
 

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You should try it with the driveline spinning the same rate, not the motor.

Check my math, but I think:

2000 rpm in 5th gear is 2387 rpm for the driveline.

2000 rpm in 4th gear is 2000 rpm for the driveline.

So get the rpms up to 2387 in 4th and see if it vibrates.

If yes, it's probably the driveline.

If no, it's probably your transmission.
 

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Sounds like it could be a fueling issue at low RPM. Generally drivetrain vibrations are consistent with on/off throttle at a specific DRIVELINE RPM. Its not *usually* effected by vehicle speed or specific engine load or RPM. In other words you should be able to duplicate any one driveline vibration in most gears.

I know the S/C trucks (including mine) lean out in 5th at low RPM and cause detonation. A lot of times that detonation feels like what you describe. It has to do with the load on the engine at higher speeds. The ecu thinks the truck has a lighter engine load at 2k (with light throttle esecially), so it leans the fuel out, but 2k at 55mph versus 2k at 45mph is drastically different. In a N/A truck its not usually and problem, but if you have a lot of carbon build up on your pistons, low fuel pressure (or flow), or too hot of plugs, it can exacerbate the issue.

Hope that helps
 

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Discussion Starter #8
Maintaining the exact same speed and driveline RPM I can go back and forth from 4th to 5th and it only does it in 5th.

As far as fuel issues, I would imagine I would see problems in other gears if that were the case but I don't. Not at all. 1-4 are perfect.

I would almost insist that my 5th gear is bad if I hadn't pulled the driveline and drove in 4x4 and seen the problem vanish. But now that my driveline is rebuilt and good as new I wonder if it's 5th gear causing vibration that resignate through the driveline.

I've seen so many posts on this but no one seems to have figured it out.
 

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How about 3rd gear? If you have some vibs in 3rd, not in 4th, and again in 5th then you have a bad bearing in the tranny. Been there with my 84 pick-up.
 

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Tashier, have you looked into what Squishy is saying? It seems like it's looking in a different area, and you seem to have ruled out the driveline possibility. Can't hurt to investigate.

I know the S/C trucks (including mine) lean out in 5th at low RPM and cause detonation. A lot of times that detonation feels like what you describe. It has to do with the load on the engine at higher speeds. The ecu thinks the truck has a lighter engine load at 2k (with light throttle esecially), so it leans the fuel out, but 2k at 55mph versus 2k at 45mph is drastically different. In a N/A truck its not usually and problem, but if you have a lot of carbon build up on your pistons, low fuel pressure (or flow), or too hot of plugs, it can exacerbate the issue.

Hope that helps
 

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I've never heard of a single gear causing such specific vibrations. The fifth gear is spinning at all times the truck is moving, but is only transfers power when the collar engages the synchros. Due to the number of teeth on transmission gears, any failure typically is accompanied by noise, usually at any speed, but different when the gear is engaged. Since the vibration disappears between gear changes, this would eliminate any driveline concerns from my diagnostic process (though maybe not entirely) and I would move to the next possibility.

I would strongly recommend checking fueling or cylinder cleanliness next. Try a new fuel filter and a couple tanks of gas with BG 44K added, new plugs, and cleaning your MAF sensor. It'll cost ~$120
 

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As far as fuel issues, I would imagine I would see problems in other gears if that were the case but I don't. Not at all. 1-4 are perfect.
You would think so from a logic stand point, but it really is a 5th gear issue. With it being an overdrive gear, the ECU is not really tuned properly from the manufacturer. This is why boosted trucks have to bump the fuel in lower RPM at light throttle. Of course the ECU has no idea the truck is in 5th gear so its tune is ok throughout the rest of the gears.

What's the update? Any resolution?
 

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Nothing in 3rd.
I'm at the end of my rope with this problem. I've searched forums high and low for over 2 years and can't seem to find any definitive answer on this.

I have a 99 Tacoma Xtra cab, all stock, no lift, that I have been plagued with a vibration with for a couple years now. There's 166k miles on the truck.

The vibration feels like it is in the driveline. It ONLY happens in 5th gear. The minute you go to 4th its gone. I've tried different pedal pressures and speeds and can't get it to occur in any other gear. The vibration is significant enough that it buzzes the whole cab, causing the dash to buzz and vibrate and my sunglasses on the dash to buzz against the windshield. The vibration generally goes away as I get up over 60 or heavy on the gas. But light pedal and 2k RPMS or less and it's buzz buzz buzz and shake shake.

I just finished having the whole driveline rebuilt by Driveline services of Portland. New OEM carrier bearing, new flange, new yoke, new U-joints and I honestly couldn't even find anything wrong with the driveshaft when I removed it. Looked perfect. Driveline services said the double cardagon (CV joint) was fine and spun it up to over 3000RPM and no vibration. However, while I had the driveshaft off I drove the truck around in 4 wheel drive and in 5th gear and no noise and no vibration.

I've read posts all over the web about this problem, people rebuilding drivelines and rear ends and still having the issue. At this point I am beginning to suspect that 5th gear may be the issue but of course that is a ton of work and I would love to have someone experienced with this issue chime in before I drop transfer case and transmission.
I have a 2008 recently mine started vibrating kinda like im lugging the engine too in 5th only but it didnt start till my idle fell lower i think its detonation an issue with the ecu, my ecu wouldnt let me go over 90 than my idle dropped now i can its crazy.
 
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