Question about auto transmission strut

[jimmy norman]

I have a 1984 gmc pickup 4x4..The motor went bad so I put a new 350 crate motor..The guy that put motor in said that I didnt need the strut braces, but now truck has bad vibration when in park or neutral..any help would be appreciated..alleyesonme@netzero.net

[rcbildr]

Wish I could help you with your question. I just can't remember what those braces are for....was a long day at work. I drove my 4x4 burb without them for a little while (had to drill & tap the holes for them) and didn't notice any bad vibrations, but then again with a diesel that may be kinda difficult.

[James McClure]

Jimmy: He's right, you don't need the struts. You have a vibration thats replacement related. The guy who put it in missed something someplace OR you have a converter problem. You don't say what the old motor was. Any new noises? let us know.jim

[jimmy norman]

the old engine i took out was a 305 it was repalce with a 350, new balancer was installed , same flywheel ,you hear a sound around the converter in park or neutral when the truck is sitting in a bind,any help ?

[James McClure]

Jimmy: It is possible the flywheel must be changed also OR, it isn't running true. Get under is and take the flywheel cover off, and while someone trys to start it watch the flywheel to see if it "wobbles" as it goes around. There might be a noise as you try to start it up too. I can't remember now but the 305 might be an "externally" balanced engine where the 350 isn't. Someone else might have the answer to that question. Good luck, jim

[old Rusty C10]

im wondering if the flex plate is cracked or if the bolts that hold the torque converter to it are loose . If the latter happened then the holes could be egged out and youll have to change the flex plate anyway

[jimmy norman]

Many thanks to all that replied to my question..I will try all the suggestions and let you all know what I find..Here is a little more info about the truck that i shouldve added yesterday...It had a 305 but I purchased a 350 crate motor to go in it...I also changed the axles from 1/2 ton setup to a 1 ton setup with a Dana 60, 14 bolt w detroit locker in rear w a 4:56 gear ratio...The axles came out of a military truck...It is a automatic I havent done anything to the trans...I was also wondering if putting a bigger convertor would be worthwhile...I was thinking of a 2,000 or 2,500 stall, but wasnt sure if it would make any difference over a stock one..Thanks again, and have a Happy Safe New Year everyone...

[Hoods69BadBowTie]

Originally Posted by old Rusty C10

im wondering if the flex plate is cracked or if the bolts that hold the torque converter to it are loose . If the latter happened then the holes could be egged out and youll have to change the flex plate anyway

x2 thats what I was wondering as well.

[James McClure]

Thats kind of what I ment about the guy who did the work missed something, but I'm thinking a cracked flexplate would have been very noticable and Jimmy didn't mention any loud noises like the plate or the converter being loose. I think it's an assembly problem or a 305 flywheel won't work on a 350. jim

[1985K10]

If the 350 is a newer engine the flexplate could very well be the problem. In 85 or 86 I believe small blocks went to a 1 piece rear main seal, and I think the balancing changed too. I had bought a 383 crate for my chevelle, i was told to use the balancer and flexplate from the same era 350.(the 383 was originally a 1986 or so 350). I did some checkin at the parts store and they listed the same flexplate for an 86 305 and a 86 350, so being cheap, I pulled the plate off my 86 parts truck(305 with 130K on it) and its been holding up just fine, no vibrations, in my 420hp chevelle! Actually I had bought a new one from Ad#$@ce Auto Parts and it blew apart in less that a week....

Sorry for the long rant but id contact the company that built your engine and find out what flexplate or flywheel they recommend.

[cjracing15]

On the one piece main or two piece?

[jimmy norman]

it has a 2 peice now

[LONGHAIR]

Originally Posted by jimmy norman

I was also wondering if putting a bigger convertor would be worthwhile...I was thinking of a 2,000 or 2,500 stall, but wasnt sure if it would make any difference over a stock one..Thanks again, and have a Happy Safe New Year everyone...

The convertor is mostly related to the camshaft, since you have not indicated that there was anything especially high performance about this engine...a higher stall convertor will not do anything for you.

Other than that, a few things....
As long as we are talking about first generation small blocks (not LTs or LSs) or the variations of one-piece rear main seals...the only externally balanced small block is the 400. Since that is not in play, you shouldn't have a balance issue because of the flex-plate. "Cracked" flex-plates usually only make annoying noises, not vibrations, but I wouldn't say that it is impossible.

I'm pretty sure that the flex-plates will not physically interchange between one-piece and two-piece style cranks anyway.

Although they have absolutely nothing to do with this vibration issue, I would put the struts back on. Lots of people get lazy and leave them off after changing starters, removing the convertor cover for transmission work, or R&Ring an engine. They help to support the entire length of the drivetrain. The bellhousing area of the transmission case can take quite a bit of strain in a 4x4 truck. The extra weight of the transfer case and the torque of an off-set driveshaft are part of this stress. The heavier lower cover and the struts that connect them to the engine block are designed to help....I would put them back, there is no down-side.

Also, you said "In park or neutral"...meaning that it does not do this in gear?

[jimmy norman]

it does not make no noise in any gears runs perfect ,sitting flat in p ark or neutral i feel a vibration , in park or neutral when truckis sittng in a bind it makes a noise near the converter what do you think it might be