[vertbird]

I have a 76 T/A 400 with A/C. I installed Classic Auto Air upgrade kit a couple of years ago. I don't drive the car much but this summer have discovered the compressor vibrates quite a bit at 3000rpm. Below that there are no vibrations but as soon as you get to 3000rpm it vibrates enough you can feel it while driving.

The original stock brackets anchored the compressor from above as well as below, this new kit uses only the lower 2 mounting holes to secure the compressor. I called Classic Auto air and they said the system may be over charged. Could this be the case or do I need to add another support brace for the compressor? Anyone else ever had this issue? Thanks!

[Formula403]

A bracket may help a little but why is it doing it anyway? The bracket doesn't solve the issue. Easy to get someone to check the pressure or settings.

[bhill86]

I installed that same kit a few years ago and experienced (and posted) the same issue. I don’t believe I overcharged mine as I used their recommended 70-80% of the original R12 capacity. I tried various amounts of adjustments and did make a small (temporary) point of contact I’ll call it to add some support. Bottom line is, their bracket sucks. Their customer service in my opinion and experience isnt much better. Anyway, my bracket seemed to help a little. I’d hardly even call it that. I don’t have any pictures handy but I took an approximately 1” by 2” piece of sheet steel and drilled a hole in to to attach it behind the nut at the pivot of that makes sense. Then I lowered the compressor until it made contact. Truth be told though I feel like what helped more was the belt “breaking in”. As in, over time without any other changes, I’ve gone down to very little vibration. You may want to give that a shot.

Also, Vintage Air has a much better bracket setup that is about $100 last time I looked if that’s a route you want to try. Hope this helps.

That said, how satisfied with your systems performance are you?

[vertbird]

Hi bhill86, the system has worked fine, no real complaints except the obvious vibrations. I was at the Pontiac show in Pigeon Forge TN and saw multiple people with additional brackets supporting aftermarket compressors but can't say they were the same as mine.

[bhill86]

Did you charge yourself or take it somewhere?

[vertbird]

Charged it myself, can’t remember exactly the pressures but I used a sheet that showed about 80% of what the R12 was at certain ambient temperatures as a guide.

[bhill86]

Gotcha. Thanks.

[HWYSTR455]

Had the same issues with the bracket, that T bar thing is junk. It breaks all the time from the vibration. The belt is super long and that thing is on stilts.

"Yeah, we'll just put a heavy-azz compressor that has a high load on a long stick to hold it in place, what could go wrong?"

I was going to go with the VA brackets but bailed and just did a march setup. Zero vibration.

Here's a pic of the 'T' adjuster on the 442, broke 3 of those things before I switched.

Sorry for pic quality, was one I had on hand.

This is the VA bracket:

https://vintageair.com/1964-81-ponti...assenger-side/

Way better, but still not perfect.

Here's the regular March Ultra Mid-Mount kit:

https://marchperformance.com/pontiac...-bracket-kits/

Should really get the one with the tensioner but the all inclusive ones are much better:

https://marchperformance.com/pontiac/pontiac-326-455/

Can search here for serp conversion kits, it's the way to go, even if it is a tough pill to swallow. You will never regret that your did it.


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[vertbird]

Great info HWYSTR455, glad I'm not the only who's experiencing this problem. Thanks for the suggested solutions, I'll definitely look into those options.

[Formula403]

And what is the vibration? How many cylinders does this new compressor have?