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YOUR RESEARCHReplaced Motor Mounts, Still feel a bump when shifting
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Install powerflex black trans insert - gone
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Performed · outcome unconfirmed
Installed the PowerFlex black trans insert - gone.
Replaced Motor Mounts, Still feel a bump when shifting
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Leading evidence: 'Install powerflex black trans insert - gone' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Install powerflex black trans insert - gone' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Performed · outcome unconfirmed · Original poster
So I replaced the engine mounts on my 99 with new oem units and I am still experiencing a slight bump when I shift gears...
Replaced Motor Mounts, Still feel a bump when shifting
Replace gear oil
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Performed · outcome unconfirmed
Replaced gear oil with some Redline about 400 miles ago, hadn't been done in quite a while but showed no signs of flakes.
Replaced Motor Mounts, Still feel a bump when shifting
Replace transmission mount
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It was like a new car after I changed the transmission mount.
Replaced Motor Mounts, Still feel a bump when shifting
Recommend yellow inserts - black are much too harsh
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Suggestion
I'd recommend yellow inserts - black are much too harsh for any road car IMO.
Replaced Motor Mounts, Still feel a bump when shifting
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So I replaced the engine mounts on my 99 with new oem units and I am still experiencing a slight bump when I shift gears... I did not replace the transmission mount, could that be it? In addition to that, should I be looking at something else?
Well then, looks like the synchro is worn in that gear and there is no easy fix for that. Try changing the gear oil. See if there are any flakes in it.
You didn't say anything about having trouble getting it into gear... If it were syncro's I'd think you'd be getting grinding/trouble getting into gear.
Correct, I dont have any issues getting into gear.... Even if I dont change gears, if I accelerate and then remove my foot from the pedal, I still feel the bump
Anything to report back OP? My 996 C4S is doing the same thing, was thinking possibly synchros but no trouble getting it into gear, just a "bump" exactly like you said sometimes on second, mostly on 3rd and 4th, sometimes 5th. Replaced gear oil with some Redline about 400 miles ago, hadn't been done in quite a while but showed no signs of flakes. 92k miles total on the car.
I had some "bumps" in certain gears if I get lazy with my shifting - eg. didn't rev match to some degree etc etc. Installed the PowerFlex black trans insert - gone. Can be as lazy as i'd like - no effect on the drivetrain.
Comes with a big big trade off on NHV so black are coming out and PowerFlex yellow are going in.
Your problem might be sinister though
Is the "bump" there when shifting, or anytime you lift off the accelerator and feels similar to a worn u-joint on an older car? If the latter could some part of the differential, a Wavetrac install cured my banging.
On a scale of Basic (1) to mechanic (10) this is IMO a 6.
- Jack up car and put the rear on two axle stands
- Remove under trays
- Support
transmission
on a bottle jack
- Undo two through bolts
- Undo 6 x nuts
- Remove transmission carrier
- Remove second transmission carrier studs
- Insert inserts (lubricate first and work into place) - best tip I can give for this is get a screwdriver and move the insert to give yourself a gap to work the insert into place
- All steps in reverse to get it all back together
I'd recommend yellow inserts - black are much too harsh for any road car IMO. Yet to try yellow but I'm not really liking the PowerFlex black...
Other tips - if possible have a impact gun only to undo the bolts (never do them up with a impact gun!!) Only use a torque wrench to tighten -
48ft-lb for all 8 bolts
For the studs I only tightened them until they were snug and tight - they are thin and you wouldn't want to snap them as they only have a 7mm head.
This is a source reference. Confirm exact model applicability in the original material.
