Hard/jerky shift from 1st to 2nd gear. (bushings perhaps?)

[ewrjontan]

So I couldn't figure out a better title but I do not mean that it is difficult to shift gears. What I mean is that, when I shift from 1st to 2nd gear under hard acceleration, I feel like there is a violent jerk coming from the driveline. Shifting from all other gears is fine.

I upgraded/refreshed basically everything last year. Poly bushings in the rear (subframe, differential, rtabs), however I used oem Front control arm bushings, oem motor mounts and rogue engineering tranny mounts. Do you think that this violent jerk is due to the fact that I am running harder bushings in the rear and the soft oem bushings up front? It makes sense to me but I am just looking for a little verification

I am wanting to run a solid shifter setup but I feel that I should probably switch to poly or solid motor/tranny mounts then.

[LockDots]

I can't speak for the rest of the issue you're having but you're definitely going to need hard poly or solid tranny mounts if you go with a chassis mounted shifter.

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[earthwormjim]

Did you replace the giubo?

[hc1001]

Maybe you didnt preload the driveshaft center support bearing forward when reinstalling?

FWIW i get drivetrain lash when accelerating in 1st and then completely getting off the accelerator. Also get it when accelerating and doing a slow 1st to 2nd gear shift. I have a 3.73 diff and 6 speed transmission(heavier).

[TostitoBandito]

Yeah I think lash/vibration when lifting is common in these cars, though probably only noticable with poly/solid mounts and/or shorter gearing. You shouldn't be feeling anything like that when on the throttle though.

I get the lifting vibration in a very specific rev range between around 2500-3000 RPM if I lift off the throttle suddenly, but I only started noticing it after putting in poly trans mounts. I'm assuming it was there the whole time, since basically my entire driveline aft of the transmission and all the mounts are brand new.

[ewrjontan]

Hmm interesting. I figured this was due to the lack of solid mounts. It's not during throttle it is exactly as you describe as lift off. Once I get off of the throttle (to shift or just to slow down) I get the violent jerk.

The guibo was replaced and I made sure to pre-load the driveshaft during install.

[TostitoBandito]

If it's "violent" as you say there's probably something else amiss. I have stiffer mounts than you and the worst mine gets is a mild vibration for a second or so like driving over a rough patch of pavement or a really mild rumble strip. If I apply a little bit of throttle, press in the clutch, or change the RPM out of that narrow window it goes away immediately.

I honestly have no idea what it could be. I know I've been backwards and forwards over mine trying to figure out if it was an actual issue or not, and I've done everything from checking the diff and rear subframe mounting/tightness, rebuilding the drive shaft, replacing the guibo and CSB, and adjusting motor/trans mount torque. I came to the conclusion that it wasn't a concern in my case, but your sounds worse. If you only notice it in certain gears, could it be something in the trans?

I know my vibration is noticeable while in any gear as long as I'm in gear and within that RPM range, though I notice it most often in 5th between 45 and 55 mph since I spend the most time there compared to lower gears where I'm just passing through. It has nothing to do with shifting, it's when the engine braking load is transferred up the driveline when I lift and something somewhere vibrates when the RPM/frequency is just right. Since it doesn't happen for me in neutral that leads me to believe it's not anything past the transmission, since all that stuff is spinning just the same. My best theory is that I just have a 150K mile trans and I can actually feel it with stiff mounts.

[Carpy2]

I have stiffer mounts than you and the worst mine gets is a mild vibration for a second or so like driving over a rough patch of pavement or a really mild rumble strip. If I apply a little bit of throttle, press in the clutch, or change the RPM out of that narrow window it goes away immediately.

Wow this is the first time I've seen someone describe what I experience perfectly. I have poly mounts and for me it's most noticeable when coming off throttle in 3rd or 4th, decelerating with just engine braking from 4k rpm to about 3k rpm. It's just like you say, like going over a slight rumble strip. I've always thought maybe it was something serious in my drive line or even the fluids I was running... many many miles later and nothings changed. Nice to hear it may at least be semi-normal...

[bluptgm3]

What is the condition of your rear shocks?


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[ewrjontan]

Just threw on some Ground control sport/school coilovers last May and with driving too/from and at the track have no more than 1500 miles on them. All bushings in the rear have been replaced with poly, except for the control arms which were replaced with the oem ball joints.

I guess it could be a tranny issue but I really don't know. I did so many upgrades/refreshes at one time including a stage 2 clutch. To me, the best way I can describe the issue is that when I let off the throttle (shifting from first to second) it feels like the motor, tranny or something else launches forward (almost like slamming on the brakes).

[Hova]

Just threw on some Ground control sport/school coilovers last May and with driving too/from and at the track have no more than 1500 miles on them. All bushings in the rear have been replaced with poly, except for the control arms which were replaced with the oem ball joints.

I guess it could be a tranny issue but I really don't know. I did so many upgrades/refreshes at one time including a stage 2 clutch. To me, the best way I can describe the issue is that when I let off the throttle (shifting from first to second) it feels like the motor, tranny or something else launches forward (almost like slamming on the brakes).

Do you still have the dual mass flywheel with that clutch?

[ewrjontan]

I am running an Fx/f1 racing stage 2 clutch and chromoly flywheel.

[bluptgm3]

Kinda sounds like possibly your clutch is not fully releasing. Are you running a clutch stop?


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[ewrjontan]

Nope, no clutch stop. If that were the problem, wouldn't it be noticeable in all gears though?

[TostitoBandito]

Maybe. I know in my car it's a lot touchier about clutch position and revs from 1st to 2nd than it is anywhere else. If there's something wrong like that, this is the first place I'd expect to notice it (not being able to smoothly shift to 2nd).

[ewrjontan]

Interesting. I will keep it in mind the next time I drive. I just honestly hate doing it because it's so rough.

[fasteddie313]

As compared to what? I assume that you are an experienced manual transmission operator and have driven many other manual cars also, and this car is unusually jerky as compared to everything?

All manual vehicles are jerky from drivetrain lash in low gears to some extent and I'd say the BMW is average. It depends on the drivetrane type and wear. More miles, more wear, more lash, more jerky, or just harder to drive smoothly.
For example the 931 has no joints in the driveshaft and has very little lash, the BMW has a couple joints so a little more lash and a little more difficult to be smooth with, the 230k mile Subaru has more joints than you can shake a stick at and has a lot of lash and is the most difficult to drive smoothly.

You can pick the rear wheels up with it in gear and go forward and back with the wheels to find the lash. Have someone else do it and feel all of the joints and diff and trans to see if their is any lash.
In the BMW it could also be caused by that rear diff bolt this is prone to braking I think, so check that..

Maybe your clutch is grabbier than usual, IMO the BMW has too much rev hang so it could be that, maybe you have a removed or malfunctioning clutch delay valve, bad diff-trans-engine mounts, bad sprung clutch or bad dual mass flywheel.

Under "hard acceleration" I burn some clutch into 2nd gear which loads up the drivetrain before letting it lock up making for a smooth shift and gets the power down fast.

Check for on/off throttle lash in all gears, it should be the greatest in the lowest gears/easiest to feel.
Make a video of you lash, your shifts, your clunks, and throw it up on youtube..


What you guys are talking about as far as the little vibration at a specific load and RPM window, I have that too a little.. Just barely on the throttle in like a 100rpm spot, thought it was the guibo but haven't changed it yet.

[ewrjontan]

Compared to how the car used to be. Obviously, it is likely to feel different going from a stock (but used...150K) vehicle to a car with many after market bushings and parts (including clutch). I'm just concerned with whether or not it is on the normal side or if it can be remedied (ie with solid motor and trans mounts).