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Discussion Starter · #1 ·
Hello, I have a question about the L67 and L36 flexplates. I know the main difference is the bolt pattern for the torque converters. Besides that, I was wondering if there is any difference between the two concerning the counterbalance? If so, by how much are we talking about?
 

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Yes, they are both balanced completely different. You cannot use an L36 flexplate on an L67 motor that is still balanced for the L67 plate (and vice vs).

However, you can use the L36 plate if you have your motor re-balanced with the L36 plate (and vice vs).



Hope this helps!
 

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Discussion Starter · #3 ·
Excell said:
Yes, they are both balanced completely different. You cannot use an L36 flexplate on an L67 motor that is still balanced for the L67 plate (and vice vs).

However, you can use the L36 plate if you have your motor re-balanced with the L36 plate (and vice vs).



Hope this helps!
Could you tell me how they are balanced differently? I only wonder because I have been using an L36 flexplate on my L67 for just over 2 years now and have not noticed any ill effects. So if they are balanced differently, the difference must not be that much because I cannot detect hardly any vibration at all. Please supply specifics.
 

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SubZero350 said:
Could you tell me how they are balanced differently? I only wonder because I have been using an L36 flexplate on my L67 for just over 2 years now and have not noticed any ill effects. So if they are balanced differently, the difference must not be that much because I cannot detect hardly any vibration at all. Please supply specifics.
The weight differences in the flexplates are not enough to cause a cataclysmic failure. However, using an L36 flexplate on an L67 will cause lots of internal ill effects. Premature bearing wear, vibration induced power loss, etc.

Think about it this way, if GM could have used one flex plate for both motors, do you think they would have used two different flexplates anyway?
 

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Discussion Starter · #5 ·
Excell said:
The weight differences in the flexplates are not enough to cause a cataclysmic failure. However, using an L36 flexplate on an L67 will cause lots of internal ill effects. Premature bearing wear, vibration induced power loss, etc.

Think about it this way, if GM could have used one flex plate for both motors, do you think they would have used two different flexplates anyway?
Thanks for the info. The only question I guess I need answered at this point now is: has anyone put both flexplates up on a balancer and determined just how much difference there is?
 

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Why is that though, is the flexplate balanced/weighted for use with the different size torque converters or for the different balancers on L36/L67s? Basically which is the matched set?
 

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Discussion Starter · #8 ·
Thanks for the info on this topic. Next question, I have found what I believe to be an L67 flexplate from a 97 Park Ave Ultra. However it has the p/n 24505214 stamped into it which does not show up on any GM p/n search. It does have the L67 crank bolt pattern, and it does have the larger torque converter bolt pattern. Does anyone have or know of this part number and can verify its origin?

On a related topic, I do have some p/n's that go back a few years. It appears that the L67's flexplate has changed p/n's several times since the 4T65-EHD came out in 1997. Is there anything wrong or defective with the earlier flexplates?

Thanks in advance.
 

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Easy way to identify. Look on the balance weight; if it has "SC" stamped into it, you're golden like a shower.
 

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Excell said:
The weight differences in the flexplates are not enough to cause a cataclysmic failure. However, using an L36 flexplate on an L67 will cause lots of internal ill effects. Premature bearing wear, vibration induced power loss, etc.

Think about it this way, if GM could have used one flex plate for both motors, do you think they would have used two different flexplates anyway?

I may have just $hit my pants...

For the longest time I cannot find the little 'issues' that have attacked our L67 GT.. and has been the only swap where we used the GT transmission, and, yes, the tq converter and L36 flex as well. The car always has problems at the top of 2 and very much so in 3.. so perhaps with first being so short, the ballance problems don't show up, and start to as the gears get longer.

I posted a thread about my tuning woes with this car in the PCM section.. but this info has me wondering....

No matter what we do we cannot gain 20 or more mph in the back half.. we trap 86 at 8.5 sec in the 1/8 but finish at 13.2's around 102-105 all the time. O2's stay at 915-930 all the time... could this ballance problem induce knock?

Next question being, L67 flex and HD Tq converter... would that cause issues with 3.29 gears? ... Or should we just get a drilled one and keep the gt tq conv?
 
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