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Old 07-06-2010, 11:49 AM   #1
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Default 4T65E on L67 - Flexplates

As some of you know, I'm having an L67 swapped into my 95 Regal. We have the engine already, and its very clean, smooth, and was well taken care of (top end gaskets are all new with metal LIM gaskets). Car was in the junkyard due to vandalism. Heavy keyed paint and broken windows.

I'm having a guy named Bob from w-body.com handle this swap since I don't have the time or space to do it myself. The problem was that when he went to pull the engine, someone had already grabbed the transmission. He spent all Thursday last week looking for a new one, so I ended up ordering one on ebay.

He'* using a 99 L36 PCM from a Monte Carlo/Lumina. This guy can wire up a PCM and wiring harness with his eyes closed.

Here are the problems I'm having so far.

I ordered a transmission off ebay for $225 shipped. I had $100 in ebay bucks so this was my best option. The transmission was pulled from a car that was bought at an insurance auction, a 2003 Buick Century, L36 + 4T65E, 86k miles. The plan here is to grab the HD parts (diff, case, etc.) from a 4T65E-HD at the junkyard and swap them over. We planned this in such a way because using the HD diff on this transmission will net me a 3.29 total FDR instead of the 2.93 granny gears on the 4T65E-HD. Also, I'll have the higher stall L36 torque converter.

However...while looking at some transmisison charts, we realized that non-HD transmissions used a smaller torque converter that bolted to the L36 flexplate, and the HD transmissions used a higher, lower stall converter bolted to the L37 flexplate. The bolt holes here do not match up, so you cannot simply bolt an non-HD torque converter to an L67 flexplate. I have heard of reports of people with L36'* using L67 flexplates with no problems, and people with L36'* using L67 harmonic balancers, but I haven't yet heard of people using an L36 flexplate on an L67.

I'm told these are balanced differently, though I'm uncertain of how.

I'm under the impression that crank balancing is done by the balance rod in the lifter valley, and the harmonic balancer. Does the flexplate actually balance anything, or is it simply weighted differently for other purposes? I've heard that a heavier flexplate will take longer to rev, but will hold power better as a result of inertia, while a lighter flexplate will rev more easily and lose its power more easily. What I'm trying to find out is, can I use an L36 flexplate on an L67? Please explain why.

If I can't use it, my only alternative is to grab the INTENSE drilled L67 flexplate which will accept the smaller torque converters.
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Old 07-06-2010, 11:51 AM   #2
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My typing is fail today.

Let me fix this:

However...while looking at some transmisison charts, we realized that HD transmissions used a larger torque converter that bolted to the L67 flexplate, and the non-HD transmissions used a smaller, higher stall converter bolted to the L36 flexplate. The bolt holes here do not match up, so you cannot simply bolt an non-HD torque converter to an L67 flexplate. I have heard of reports of people with L36'* using L67 flexplates with no problems, and people with L36'* using L67 harmonic balancers, but I haven't yet heard of people using an L36 flexplate on an L67.
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Old 07-06-2010, 11:56 AM   #3
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You can get a drilled flex plate, or swap them. I'm running a L36 on my engine, so if you need a L67 plate, let me know.
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Old 07-06-2010, 12:01 PM   #4
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Quote:
Originally Posted by Danthurs View Post
You can get a drilled flex plate, or swap them. I'm running a L36 on my engine, so if you need a L67 plate, let me know.
I have a guy who I can get an L36 flexplate from, so that won't be a problem. So you're 100% sure that I won't have any problems? Just want to get a confirmation since I've gotten a lot of conflicting information from people, many of which don't really have any experience with this.
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Old 07-06-2010, 12:04 PM   #5
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I'm running my L67 with a L36 flexplate. So it works. You can also use your other torque converter to match the flexplate.
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Old 07-06-2010, 12:10 PM   #6
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Alright, thanks. I'll get an L36 flexplate.
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Old 07-06-2010, 01:24 PM   #7
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The balance is ever so slightly off. Dan being cammed wouldn't be able to notice it, because of the cam lope. It'* a common swap out.

You could egg the holes in your L67 flex.

A third option is you could get an L26/L32 flex that is double drilled for either converter.

I've done all three with the same success.
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