258/360 flywheel balancing

[scotty]

we are installing the t18a from my 82 j20 into an 85 xj cherokee equipped with an 81 258 six cyl.

my question is should we use the flywheel that came from the 360,and matches the t18,or should the flywheel match the engine? the 360 pressure plate does bolt to the 258 flywheel. looking at the back of the flywheels,it certainly looks like the 360 flywheel is maybe balanced with the engine-its definately different than the 258.

our initial thoughts are that the 360 and 258 are balanced differently, and that the flywheel should match the engine. any thoughts?



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scott
85 grand wagoneer
258 with motorcraft 2bbl/904/twin stick dana 300/dana 44/welded amc 20
38x15.5 gumbo mudders
snorkel/dual batteries/onboard air/"custom" convertable
3 inch body lift/mostly stock suspension/"modified" fender openings
custom front/rear bumpers and brushgaurd

possible small block chevy "test" swap in near future

[PAJEEPER]

I remember reading in an issuse of Four Wheeler that all AMC flywheels are balanced to the engine they came with so you will have to use the 258 flywheel.

[Michael F]

The 360 is externaly balanced and I believe the 258 is not. The local parts places will tell you that the auto flex plates are the same for the 360 and 258, they are NOT!

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Michael Forman
81 Cherokee Laredo WT
51,000 orig. miles
360/727/208/3.31/31x10.5AT
79 Cherokee Chief WT (snow plow)
360/400/QTw/LR/31x10.5
My family has 7 FSJ's!!!

[scotty]

HEY JOE!

dont they take the same part number?

i can see no weights,or visual differences between the 2(i have both here) so what is the difference?

there are different convertors for the v8 and six,so any differences in balancing are probably in the convertor.i put mine together with the convertor from the 258,so in a couple of days ill be able to tell you for sure if it shakes or not!



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scott
85 grand wagoneer
258 with motorcraft 2bbl/904/twin stick dana 300/dana 44/welded amc 20
38x15.5 gumbo mudders
snorkel/dual batteries/onboard air/"custom" convertable
3 inch body lift/mostly stock suspension/"modified" fender openings
custom front/rear bumpers and brushgaurd

possible small block chevy "test" swap in near future

[Michael F]

Scott You can come see mine! They are different and the t/converters just have different stalls. I am using the 258 converter with my 360! The 79 400 flex plate looks like a 3 spoke wheel whith 1/3 of the flex plate almost solid, definetly balanced! I called everybody in town they all told me the 360 and the 258 used the same plate, except for the dealer and Don's Trans up on 49 and 40. I ordered the plate for a 360/727 from him and it looks like the 258 but with a wieght welded to it!! I have no vibration problems, just give Don a call.

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Michael Forman
81 Cherokee Laredo WT
51,000 orig. miles
360/727/208/3.31/31x10.5AT
79 Cherokee Chief WT (snow plow)
360/400/QTw/LR/31x10.5
My family has 7 FSJ's!!!

[scotty]

hmmmmm... the 360 flex plate that i have has no weights on it,but that i guess doesnt mean that it is the correct one,just because someone was usig iton a 360.anyway,its in there now,so ill see what happens- i may need to give your guy a call if its got some funky vibes. im glad youre using the six convertor,i didnt really want to buy a new one of those.the one ive got is brand new and has a drain plug.

thanks for the info



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scott
85 grand wagoneer
258 with motorcraft 2bbl/904/twin stick dana 300/dana 44/welded amc 20
38x15.5 gumbo mudders
snorkel/dual batteries/onboard air/"custom" convertable
3 inch body lift/mostly stock suspension/"modified" fender openings
custom front/rear bumpers and brushgaurd

possible small block chevy "test" swap in near future

[Manhattan]

The 360 flywheel and the 258 are not the same. the bolt pattern is identical but they are very different. I made this mistake - 258 flywheel on a new 360 (in a CJ) it vibrated terribly.

[scotty]

thanks for the insight. i strted thinking about it,and decided that id rather take it back out now,with only 2 bolts in the belhousing,than later,after its all back together. so earlier today i took it out and compared it to my old cracked 258 flexplate,another supposed 360 flexplate,and a 360 flexplate a friend of mine had. sure enough,the one that my friend had,which was definately from a 360,had a weight on it.

i am very glad to have discovered this early,and am now using the correct 360 flexplate. thanks again for the responses! http://www.cs.colostate.edu/~zeimet/ubb/tongue.gif



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scott
85 grand wagoneer
258 with motorcraft 2bbl/904/twin stick dana 300/dana 44/welded amc 20
38x15.5 gumbo mudders
snorkel/dual batteries/onboard air/"custom" convertable
3 inch body lift/mostly stock suspension/"modified" fender openings
custom front/rear bumpers and brushgaurd

possible small block chevy "test" swap in near future