Nose drops on 1st / 2nd gear shifts or letting off throttle after acceleration

[annihil8ted]

When I'm shifting from 1-2 and sometimes 2-3 or when I'm coming off throttle/acceleration, the nose seems to drop and it feels like I'm being thrown a little forward. If I'm not smooth with the power on the next gear, the vehicle will feel like it bucks. Not fast/high frequency like clutch shudder but slow bucking, maybe once or twice?

I know a little bit of this is normal (acceleration puts weight in rear and vice versa but it feels excessive. How do I reduce this? I have new shocks, control arms, and springs so I don't believe this is due to slop in the suspension.

Sometimes, when shift off of 1-2 super fast, I do hear a little bit of clunking. This is leading me to think maybe something is loose in the drive train? Is it possible that I have excessive slop/backlash in the driveshaft? I'm also looking at the transmission mount as I'd wager that it's around the same age as the control arms I took off and those bushing were long past gone. I will say that there is no clunking unless I'm clutching really really fast in and I'm also not experience any vibrations.

This clunking, while not happening very often, occurs at all RPMs shifts.

 

[Chris]

I wonder how much of it is your driving.

I'm not saying that to be rude, but I've noticed that more often than not people have different driving styles and often times it can cause issues like this. Maybe have someone else drive it and see if it does it for them as well? Just trying to eliminate the simplest explanation first.

As for the clunking, that is possible something is loose but the only way you're going to get that figured out is to get it up on a lift or jack stands and do a dry steering / suspension test with the help of a buddy or two.

If the problem you're dealing with is an engine problem, there should be (or will be soon enough) a check engine light with a code.

 

[BlueC]

Sometimes, when shift off of 1-2 super fast, I do hear a little bit of clunking.

Why are you shifting "super fast"? Are you attempting to race someone? Excessively fast shifting puts undue stress and wear on syncros.

I'll guess this is pretty much all your driving style. I shift my Jeep with 2 fingers, not a full fisted death-grip, jerk and slam movement. Try accelerating and shifting in a smooth, relaxed manner.

 

[jjvw]

Up shift at a higher rpm.

 

[annihil8ted]

I wonder how much of it is your driving.

Definitely a possibility! Although I will say that between multiple TJs and other manual cars, I've only felt this with some TJs.

Why are you shifting "super fast"?

Sorry, let me clarify, it's when I clutch in really fast, not shift super fast. I'm still clutching out normally when I do, it just clunks when I clutch in really fast. As far as driving style, I do try to drive smoothly when possible. I'm usually two fingers (and pinkies up) and if I encounter the rear situation where the gear is sticking, I'll instantly go to another gear before shifting it into the desired gear. I'd say for actual shifting between gears, it's average speed, I'm definitely not trying to bang through all the gears as quickly as possible

Up shift at a higher rpm.

Higher than 3.5K? On 33s, with 3.73 (to my knowledge), I'm usually shifting out of 1st at 3-3.5K. Should I be shifting even higher?

I've also not noticed a correlation between RPMS and the clunking/dropping of when I move my foot off the pedal or when I clutch in after accelerating (foot is off the gas again here)

 

[BlueC]

I'm usually shifting out of 1st at 3-3.5K

That should be fine. That's where I'm generally shifting. Some people come one here and tell us how they shift before 2K, and that's probably what JJ assumed you meant.

 

[annihil8ted]

That should be fine. That's where I'm generally shifting. Some people come one here and tell us how they shift before 2K, and that's probably what JJ assumed you meant.

Ah that makes sense, I probably should have also mentioned this was occurring at all RPMs in my original post


I will say it doesn't happen often, and I can definitely shift smoothly pretty easily but it still happens. I'm trying to chase this down because on paved roads, it's easy to anticipate the drop if it comes to that but when off roading, the bucking between 1-2 and really annoying.

I guess I would categorize it as it feels like there's energy stored or out of sync in the drive line. Like when applying power, something is twisting and holding some energy and off throttle, that energy gets released so there's a mismatch between throttle on and off.

Does anyone here think this could be potentially due to the transmission mount?

 

[annihil8ted]

Had an extra hour yesterday and decided to do the transmission mount swap. Visually inspecting before doing anything, everything looked good but after taking dropping the skid plate and taking off the mount, I could see that half of the rubber had detached from the mount and I could flex with my hands the old mount where as the new one was really stiff.

Threw the new one in, bolted everything back up, took it for a spin and wow, big difference!

For one, power seems more linear and more "instant". I'm guessing this is because less twisting and shifting is occurring. Gone is the clunk from stepping on the clutch too fast or clutching in after accelerating. Vibration seems to have gone down already too

There still is a little bit of a nose rise and drop in first gear but it's much more manageable now. I'm now curious to see if replacing the motor mounts; most of the rubber and bushing seems to be original so it's due for changing potentially anyways. Will check to see if the motor is moving before I go down this path though

 

[annihil8ted]

Want to follow up with this, I finally got around to installing motor mounts too. Did the passenger side first and it helped a lot with the bucking whilst quieting down the vibration. Not as much as the transmission mount change but still a noticeable difference. A few days later I installed the driver side. There’s more vibration now (which I assume is normal and also I’m not 100% I bolted and torqued the engine bracket to block and the 3 bolts correctly) but there’s even less bucking now. It’s almost completely gone, I think the last bit of it may be excess play in the gears and perhaps too pliant of a suspension

 

[annihil8ted]

Another update now we're 3 months in. The bucking is back. Slight inputs on and off the gas in first gear causes the front of the jeep to jerk up and down. I'm now wondering if the mounts I've put in are absolute trash and have soften which is allowing the driveline to twist and untwist, causing the jerking motion

 

[GoldenGorilla]

Did you use the Anchor brand mounts? These seem to be most similar to the factory ones among the options today.

 

[annihil8ted]

No, the issue is likely that I cheaped out on the mounts and now I'm paying for it . So lesson learned and now I'm looking into more quality mounts to avoid this issue. After I finish replacing my starter which died suddenly on an accidental stall in the middle of the freeway