Robin 993 c2

I am suffering from axle trap when accelerating hard in 1st gear. If I try to do a standing start, or just get into wheel spin the rear of the car starts to feel like it is bouncing. It is quite violent.
I am fairly sure that it is the engine and transmission bouncing in the chassis as the normal result is that the car jumps out of gear.
The car is a manual C2 with 350 hp and 100,000 miles on the clock.
The question is what can i do to fix it? is it engine/transmission mounts or am i looking for dampers and springs.
I know that i sould not be such a hooligan, but it is fun.
Regards
Robin

andrew911

I did a drop clutch start once in a 1978 911 I had years ago- it had the same hop you speak of (except with only 180 hp)...I never did it again with that car after the one time, and have never done it since in any of the other 911's I've had. Very very bad for the car- all the weight is over the drive wheels giving strong grip and causing the resulting axel hop and extreme abuse to the clutch, driveline parts, joints, etc, not to mention the tires. In a high torque V8 with light rear (ford mustang type of car), the wheels break loose so quickly it's less abusive to the drive-line (although certainly still abusive) If you like your car, you'll stop doing this. If you don't care, it's going to get pretty expensive pretty quickly....because you'll go through the engine mounts and transmission parts at an incredible clip!

Nice looking car by the way!

GrantG

Do you have LSD? Just curious...

97Targa

Nothing to brag about, much the opposite, but I broke a VW transaxle (case) in half once due to severe wheel hop. That cured me.

Robin 993 c2

Please dont get me wrong, i an not going out trying to provoke this situation, but get into it when i accelerate hard, in gear foot off clutch, not dropping the clutch at a standstill.
The car has an open diff.
Maybe the answer is to change to 2nd before getting too hard into the throttle, With other 911s that i have driven the problem has not been present.
Robin

Bull

Sounds like a broken mount of one kind or another to me. Never had the problem with several cars and many rapid launches.

kkim

I agree.

Geoffrey

the fix is simple, insert 1" block of wood under the accelerator pedal.

Robin 993 c2

Thanks all
I will go for the block of wood modification until i can get a look at the engine mounts, I think that the first place to look will be the gearbox mount, i understand that Porsche fit a stiff one to cup cars.
I will let you know what I find.
Happy new year Robin.

Geoffrey

There is a large rubber "donut" where the trans mounts to the cross member. The crossmember itself is mounted metal-to-metal to the chassis. There is also another stabilizer piece that the street cars have which attaches to the bottom of the transmission. I'm not sure what the 964 cup cars used for the transmission mount, but it is still rubber. The later Cup cars replaced the "donuts" with plastic bushing which are shown in the picture below. They also removed the bottom stabilizer piece. I would assume that if you replaced the transmission mount with the solid plastic one, you would also want to run the solid engine mounts so as not to allow the drivetrain to twist and crack the housings (either engine or trans).

It is not uncommon to have the rear of the 911 hop if you spin the tires from a stop, especially if you are running wide tires.