86VERT

1986 Pace Car - When I shift from Park to Reverse it shifts quietly , from Park to Drive it clunks into drive. Any ideas and thanks in advance

billschroeder5842

I'd be looking at your U joints. You don't mention the miles, but if they have never been changed to probably need to change all 6. Beside the noise, bad U joints are a legit safety hazard.

86VERT

Thanks , if it was U joints wouldnt it clunk going into reverse also ?

billschroeder5842

Not always. A quick test would be to raise the car off the ground and with your hands on "10 and 2" move the wheel back and forth. If you have movement and clunk noises, you need to take a hard look at your U joints as you may have problem.

86VERT

I'll try that , thanks for the help. Car has 83k original miles.

arbee

Has it always done this or just started doing it? Your 86 does not have the auxiliary valve body, which is essentially a P/D - 1st accumulator.

86VERT

Just started recently

ctmccloskey

I would have to agree with Bill above, it certainly "sounds" like the U-Joints. Look for rusty powder near the joints and you might figure it out quickly.

Try to listen to where the noise is coming from as there are other things that can shift, potentially making the noise you hear. On the 1986 Corvette you were still using the mini drum for the "Parking Brake", I had a clunking noise from my C3 with that setup prior to rebuilding the Parking Brake.

You might find it even easier if you could raise the car while somebody moves it from Neutral to Drive and from Neutral to reverse so you can watch the parts to find the exact cause of the clunking. Replacing the U-Joints is a pain in the butt So buy the best ones that you can afford. If you have normal horsepower then you might want the grease fitting U-Joints, I use them on my C4 but not on my C3. My C3 snapped a half-shaft U-Joint after an aggressive start and it failed probably because it was drilled internally (for the grease fitting).

Good Luck and "May your Clunk Disappear" as quickly as it came on!

86VERT

Thanks for the help , I ll use the advice and hope for the best.

Jims66

Also look at your motor mounts..... Ask me how I know to do this.

Zip Corvettes

It can also be in the differential. The D36's were bad about the carrier wearing at the spider gear pin. What you are hearing is the pin shifting in the carrier and it's pretty loud when it happens.

vader86

Likely U-joints, if its time to replace 1, do all of them at the same time. Spicer only.

86VERT

Yes , Ive heard it could also be motor mounts, but sounds more like underneath the car

ctmccloskey

By the way,

Welcome to the Corvette Forum!

We are glad you are here helping us learn all we can about these cars we like so much!

The Spicer U-Joints that were suggested by "Vader86" is the way to go for quality U-joints that will last a long time.

But first, get the car on a lift so you can find the source of the offending noise so you know what "needs" to be fixed.
I did this test on my 1968 C3 one time when I had a clicking coming out from behind the car at low speeds, we put it on a lift with my wife inside, she started the engine put the car in gear spinning the wheels slowly while on the lift. Right away we identified the sound and it's source, problem solved!

I am pretty sure you will resolve this issue very quickly once it is identified, and hopefully inexpensively. There are a lot of interesting theory's on this sight, be sure to cross them off the list as you go. The experience at this sight is unbelievable and it is all available to you for the taking. Good Luck and be sure to tell us what the noise was when you have it figured out!

confab

Now that is interesting.. Thanks for the post.

I know mine makes a distinctly different (and fairly loud) noise engaging in reverse.. And I know it is NOT, trans, u-joints, wheel bearings, teflon washers, nut torque, etc..

The diff is the one part of the car I have never had apart.. But someone has.

SLVRSHRK

Not hijacking the thread, but I am very interested in this one and wish you luck. My 86 has the same issue. Shifts smoothly and without a clunk from Park to Reverse, but dropping it into Drive causes a jolt and noise.

Thus far on my car I have replaced all 6 u-joints, replaced the motor mounts when I rebuilt the engine, no dripping from rear D36 carrier.

I've owned the car for a year, but really only about 1K miles since getting the motor finished and everything correct. Everything else is butter smooth on the car, but it has had this behavior the whole time.

arbee's point on the accumulator is very interesting.

86VERT

I havent had the time to get into the fix yet , but I have alot of ideas about what it could be. Once i get the problem fixed I will let you know what i found.

SLVRSHRK

Best of luck. I hope your fix is one of the mentioned ones!