2000 Grand Prix "reverse slam" with 4T65E-HD trans


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2000 Grand Prix "reverse slam" with 4T65E-HD trans

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Auto Repair Home>> Automotive Repair>> Transmission Problems

richards
New User

Dec 22, 2018, 8:14 PM

Post #1 of 3 (2223 views)

2000 Grand Prix "reverse slam" with 4T65E-HD trans	Sign In

Hello everyone!

I'm driving a 2000 Pontiac Grand Prix GTP, 3.8L supercharged. Transmission is a 4T65E-HD (as far as I'm aware, I think it's the original transmission). The car has 137k miles.

The issue first popped up a few months ago where the car would make a bit of a clunk noise a give a light jolt whenever I shifted into reverse from whatever gear. It's been slowly worsening over time with the clunk getting louder and the jolt getting progressively harsher. This morning, I started the car and let the engine warm up to operating temperature, put it into reverse and the engine cut out and I had to restart it. Shifted into reverse as usual after restarting the car, still with the reverse slam (I've seen this issue referred to as such on some Saturn forums). I will also sometimes get a clunk when accelerating in reverse, but this isn't entirely consistent.

Here's a video showing the movement of the engine shifting between park and reverse. You can also hear the clunk from the outside but it tends to be louder inside the car.

Check engine light isn't lit, ECU is throwing no codes. Trans fluid is still red and not too dark.

Any ideas on what to do about this/has anyone seen this before?

Thanks!

gsferraro
Veteran

Dec 23, 2018, 12:23 PM

Post #2 of 3 (2185 views)

Re: 2000 Grand Prix "reverse slam" with 4T65E-HD trans	Sign In

Hello,
This is not a common issue, i rarely see this. How is forward engagement and how does it upshift? when slowing down to a stop in drive does the engine stumble like it wants to stall? Have you checked your engine mounts and axles? Gary

richards
New User

Dec 23, 2018, 8:15 PM

Post #3 of 3 (2167 views)

Re: 2000 Grand Prix "reverse slam" with 4T65E-HD trans	Sign In

Shifting into drive will sometimes produce a very slight clunk now that I think about it a bit more. Running through gears 1, 2, 3, and 4 is as smooth as ever. Slowing down is smooth as well, no stumble.

I looked at the engine mounts a couple days ago and they all seemed good (one was replaced four months ago), haven't looked at the axles yet. I'll check them in the morning and leave an update.

Thanks!

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