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6.2 Diesel - Rear engine vibration

scottystills

scottystills

1/2 ton status
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Calgary, AB
So I've just finished swapping my 700R4/208 for an SM465/205. Redid basically everything else on the truck at the same time. Finished half the dash and the ignition wiring today and fired it up for the first time in a year or so. Went smoothly save a little airlock.

What's happening is I've got a light ticking noise and a pretty solid vibration coming from the back of the engine, both are RPM dependant and both are there whether the clutch is in or not.

Anyone ran into something like this before? I really don't want to run the engine if something's out of balance, but I don't have the foggiest what could possibly be.

Swapping from an automatic to a manual, is it a different harmonic balancer?
 
scottystills said:
What a silly question! Who would even THINK about using the wrong flywheel? Sheesh!
Click to expand...

Ok that might have been an exaggeration, because it's totally a flywheel out of the 350 it was originally attached to.

BUT I did it with good cause, because if I burn a clutch of something in the drivetrain I want to be able to swap it out really quick. I need the practice. Totally on purpose I swear. :whistle:
 
scottystills said:
BUT I did it with good cause, because if I burn a clutch of something in the drivetrain I want to be able to swap it out really quick. I need the practice. Totally on purpose I swear.
Click to expand...

Ok that's a lie. I didn't even think about it just started bolting things up. Sigh.

Actually on the plus side after reading your post late last night (and after throwing a not-so-brief hissy fit) I started doing the Kijiji search and found a sweet deal on the flywheel I need, the 6.2 it's attached to, and a full spare sm465 with all the shifters/linkages/etc. Full accessory rack, newish IP, good deal. Picked it up this afternoon for $500.

My penance is going to be the fully deserved ridicule, and uninstalling and reinstalling the drivetrain I just finished putting in. :doah: Insult to injury I've got to travel for work this week so have 5 days in Raleigh to sit and think about what I did without being able to reach my wrenches and fix it...

Thanks though! Can't BELIEVE I did that...
 
upside is you scored a nice pile of spare parts along with the flywheel.
 
I'm confused,have I just read that a sbc 350 flywheel will bolt up to a 6.2's crank??..I assumed they would not..never bothered to try one of my old flex plates on the junk 6.2 I have on a engine stand to see if the bolt pattern is the same..if it is,I wonder if a gas 350 flywheel could be re-balanced to work on a 6.2?...:confused:
 
375 H&H said:
upside is you scored a nice pile of spare parts along with the flywheel.
Click to expand...

HUGE pile of parts! Wish I iddn't have to pull the drivetrain apart and had more time to sort through it all when I get back. haha

diesel4me said:
I'm confused,have I just read that a sbc 350 flywheel will bolt up to a 6.2's crank??..I assumed they would not..never bothered to try one of my old flex plates on the junk 6.2 I have on a engine stand to see if the bolt pattern is the same..if it is,I wonder if a gas 350 flywheel could be re-balanced to work on a 6.2?...:confused:
Click to expand...

Yep it bolted right up, and the 6.2 friction and pressure plates went right up to it without a hitch. I'm not sure if you could rebalance the 350 flywheel or not, but not sure if you'd want to. Looking at them the 6.2 looks twice the size of the 350. You'd want the extra weight to take advantage of the diesel added torque, no?

When I get back and pull the 350 one back out, I'll take a side by side shot for comparison.
 
Sometimes the interchangeability that GM designed into these trucks is great... other times not so much.
 
Yeah,the "The're ALL the same" syndrome can get you in trouble sometimes..just because something will bolt up,dont mean its the "right part"....

That is how a friend bought a 1974 GMC 3+3 crew cab 4x4 cheap,someone dropped in a small block at a service station for a customer when its original 350 blew,and the couldn't get it to run smooth,it shook like a paint shaker at idle,and had a bad vibration at higher speeds...the customer refused to pay for the install,after 6 months the station demanded payment,or the title to the truck...

The customer said "keep the POS,I already bought another truck--but your not getting the title"...when I asked if the truck happened to be for sale the owner of the place told me the story,and said "We're gonns have to scrap it soon,so if you want it without a title I'll take 400 bucks for it--thats what I was going to charge for swapping engines"...

When I popped the hood to look it over,the first thing I saw was the half moon cut out on the harmonic balancer..(and smiled,said to myself I bet the flexplate is the wrong one!)...

.I looked the rest of it over ,it was a bit rusted,but nowhere near as bad as they usually are around here..I called a friend in NH that has a used car lot and license,he ended up buying the truck ,and NH did not require trucks over 10 years old to have a tilte,unlike here,so he was able to title it up there without a hitch...all he had to do was put the 400 small block flexplate with the balance weight on it and it ran smooth and nice!..the guy used the one off the original 350,that was his only "mistake"...

My friend gave me first dibs on buying the truck,but I already had 3,and didn't really need a crew cab..so he sold it a few weeks later for 2500 bucks after doing a little body patching and puttying..

I'm rather surprised they used the same bolt pattern on a 6.2 crank as a gas V8,when the flywheels wont "interchange"...:doah:
 
You know that got me thinking, and likely incorrectly... Would you be able to use a SBC flywheel on the 6.2 by matching it with a HB from a SBC as well?

Not the way I'm going obviously with a fancy actual 6.2 flywheel sitting at home, but just spitballing.

Which reminds me, I am DYING to get home on Friday and get this replaced and purring like an old dying diesel kitten! Damn work...
 
diesel4me said:
I'm confused,have I just read that a sbc 350 flywheel will bolt up to a 6.2's crank??..I assumed they would not..never bothered to try one of my old flex plates on the junk 6.2 I have on a engine stand to see if the bolt pattern is the same..if it is,I wonder if a gas 350 flywheel could be re-balanced to work on a 6.2?...:confused:
Click to expand...

Ok here's the side by side. In all these pics the 6.2 flywheel is on the left.

Friction surface:



Side profile. Not not only the thickness but that there's probably 1/8" of material or so behind the starter ring on the diesel flywheel.



Backside. See how much more material, and it's got to be twice the weight.

 
They bolt up. When we put a 350 (that was mated to sm465) in the CUCV I think the discrepancy was flywheel tooth count/starter. Been a while I forget the details, we had the 6.2 flywheel/starter, the 350/sm465 flywheel/starter.

I know we bought a starter, perhaps we used the 6.2s flywheel. It's all kinda fuzzy. Either way it was the 350 mating to the cucv's th400. None of that is really pertinent here.

Hey, pilot bearing? Going from the 700r4 to sm465. As far as the rear vibration.
 
I think the starter drive has a different tooth count on the 6.2,when I had to buy one for my truck the thing new cost 70 bucks,I found a NAPA rebuilt for 35 bucks ..

I'm surprised GM uses the same bolt pattern on a diesel VS gas--that would encourage someone to use the wrong flywheel--but then,you can bolt a 400 SB or 454 flywheel on any other gas engine too,and have it be "wrong"...:doah:

It kind of sucks you do need a specific diesel only flywheel,because that makes it harder to go with a manual tranny,around here there aren't many diesels period,and 99% of them are TH400's or 700r4's behind them,not manuals...so finding one for a swap at a salvage yard wont be easy or cheap..and new they must cost a small fortune,if you can still get one..
probably cost as much as a used SM465 and transfer case IF you can locate one..
 
You mentioned easy clutch swaps with the 350 flywheel I think...

The clutch stuff should be the same either way. Only the disc itself is dependent on the splines of the tranny shaft.

It is only the engine correct flywheel that matters, and as you have found out there is a huge difference in flywheels. The 6.2 also has a specific flex plate.
 
Well I'm very happy to report that swapping in the new one makes the engine a LOT happier. No more vibration, no more noise. Went for a quick cruise runs like a beaut.
 
:thumb: I hate changing trannys. Glad that fixed it for ya.
 
Only thing worse than changing trannies is changing it the day after you put it in...

Never making that mistake again!
 
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