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Old 01-15-2020, 04:18 PM   #1
gainey261
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Default Need Help Shaking out a Vibration

Okay everyone, been having a vibration since my rebuild and I was wondering if you all could give me some general information so I can try and isolate/prevent myself from sinking more time and money in it.

Build:
1974 2wd 100 series with 345 and a Sniper 2300 efi bolted on, DUI dizzy. Originally 3 on the tree, but converted to T407 during this rebuild. Has the Dana 44 rear, FA5 front suspension and B&M shifter in the floor for the 727.

Tranny donor was a 71 1110 that had a 392 and the 727 in it. Had the trans rebuilt and a new TC with the kit (didn't do the rebuild of the tranny myself, had "a guy" do it for me). I did the installation myself which is most likely where the issue lies. Wanted to drop the 392 in, but the block wasn't cast for the side motor mounts for my suspension so I had to go back with the 345. Since the bell housings were the same, I just assumed all was the same but we all know what assume means.

Installed the crankshaft hub then the flex plate, made sure the TC was engaged on the shaft and bolted it all up nicely after the 6th attempt with the tranny dipping forward and me catching the TC. The only thing I had aligned during this was where the roll pin was on the hub and flex plate. Given the conversion that was being made, had a new driveshaft made and had it balanced as well on an axel-line machine.

Vibration occurs around 2300rpms in park or neutral and at highway speeds around 50 and 65. Can definitely tell its a "spinning" vibration and it feels like its right beside you in the cab.

My big questions are this. Is the flex plate for the 392 balanced differently than that of the 345, like is it balanced to counter the engine weight or is it just balanced to itself? Also, the TC came with the kit so is there a difference in the 727 IH build and I have the wrong TC (direction on the right one needed)? Given the vibration we are most likely going to just replace the TC either way to avoid damage.

Thanks in advance!
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Old 01-15-2020, 07:03 PM   #2
Scoutboy74
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Default Re: Need Help Shaking out a Vibration

IH engines are externally balanced, so the ring gear is part of that balance equation. You could have the flex plate neutral balanced at a machine shop. When you're driving, have you tried shifting the trans neutral to let the engine rpms drop to see if that has any effect on the vibration at road speed?
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Coal Trickle - '99 Ram SLT 2500 Q-Cab SWB 4x4 - 5.9L 24V CTD/NV4500/8800# GVW/12K# winch
Hooty - '74 SII 4x4 - 392/TF727/D20/3.73 D44's/Spartan FA/Powr-lok RA/33g Fuel
Lemuel - '73 1210 Reg Cab 4x4 CS - 304/TF727/NP205/4.09 FA25 & 4.10 RA16/6800# GVW
Organ Donor - '72 1210 Reg Cab 2WD - seized 392/TF727/7500# GVW
Mongo - '71 1210 Reg Cab 2WD - 345/TF727/4.10 RA17/6100# GVW
Li'l Kenny - '75 Kenworth W900A 7 yard dump - 350 small cam/Fuller 9 speed/4.11 RA
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Old 01-16-2020, 04:59 AM   #3
gainey261
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Default Re: Need Help Shaking out a Vibration

Thanks Scoutboy I forgot about that, I have shifted into neutral and the vibration goes away. So its definitely tied to the engine rpms. When I let off the gas in gear at highway speeds the vibration does get worse as it pitches forward before decelerating.

I'm going to slide the tranny back next week and get a look at it again using a lift this time. I have a feeling this is a simple problem that I'm overthinking, but I've been trying to isolate this for over a year now and most people in my area wont touch this thing because they know nothing about it.
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Old 01-16-2020, 09:38 AM   #4
Winchested
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Default Re: Need Help Shaking out a Vibration

Is the crank pulley/ dampener original? These are also externally balanced, cant remember if the pulley body is drilled for balance while attached to crank or not.
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Old 01-16-2020, 10:32 AM   #5
gainey261
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Default Re: Need Help Shaking out a Vibration

The dampener is an original dampener but I cant say it's the original for this engine. I have 3 laying around and I remember one of the dampener separated from the pulley so I discarded it. Is there a difference between the 392 and 345 dampener or are they the same?
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Old 01-18-2020, 08:57 AM   #6
gainey261
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Default Re: Need Help Shaking out a Vibration

Been doing some searching and reading and have found several mentions toward the TC for Chrysler's had a balancer installed to bring the engine assembly into balance. At this point I'm not sure which TC I have but when we get it off I will identify it, but can anybody point me towards the correct TC for this trans?
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Old 01-22-2020, 02:13 PM   #7
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Default Re: Need Help Shaking out a Vibration

R17, CR51, and 746 (no letters) are some numbers that will get you headed in the right direction. Searching parts websites using your vehicle data for this torque converter will be nearly fruitless. What you're looking for is a non-lock up converter for a Torqueflite A727 (TF8) with low stall in the '72-'75 model year range having a 12" diameter and 24 input splines. The flexplate bolt pattern is also a determining factor. AMC vehicles of similar vintage with V8 engine and A727 trans used exactly the same converter as IH, so that's another useful hint. Installing a re-man converter is generally considered part and parcel of any thorough auto trans overhaul. Not doing so is a sketchy practice. The one you have is likely correct for the application, but could probably stand to be refurbished or replaced. Taking it to a reputable auto trans shop would likely verify if it is the correct one or not and might open avenues for proper replacement.
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Coal Trickle - '99 Ram SLT 2500 Q-Cab SWB 4x4 - 5.9L 24V CTD/NV4500/8800# GVW/12K# winch
Hooty - '74 SII 4x4 - 392/TF727/D20/3.73 D44's/Spartan FA/Powr-lok RA/33g Fuel
Lemuel - '73 1210 Reg Cab 4x4 CS - 304/TF727/NP205/4.09 FA25 & 4.10 RA16/6800# GVW
Organ Donor - '72 1210 Reg Cab 2WD - seized 392/TF727/7500# GVW
Mongo - '71 1210 Reg Cab 2WD - 345/TF727/4.10 RA17/6100# GVW
Li'l Kenny - '75 Kenworth W900A 7 yard dump - 350 small cam/Fuller 9 speed/4.11 RA
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Old 01-24-2020, 04:40 PM   #8
Robert Kenney
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Default Re: Need Help Shaking out a Vibration

Just some of my insight on external balancing and the converter. I don't think you would never use the TC to balance an externally balanced engine. The balancer would simply wobble around as it spun on the flex plate.

In order to see if the 392 and other SV v8's used the same weighting on the front and rear crank appendages, you would need to look up part numbers across the 4 displacements.
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Old 02-22-2020, 05:15 PM   #9
gainey261
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Default Re: Need Help Shaking out a Vibration

Alright folks, been a long road and I still don't have any answers on my vibration. I believe I have ruled out as much as possible now, so here is what I have done.

Put a new TC on her, no change in vibration.

Put on jack stands and ran it, vibration was there at same RPM range, 1800 to 2k. Drive shaft had no wobble. Pulled the axel shafts and diff cover, replaced axle shaft bearings and seals, pinion bearing and seals, serviced the carrier. Got some lash, but all in all still works good.

Pulled the drive shaft out and ran it, vibration still present at the same RPM ranges. Put on a new dampner (the newer design without the rubber isolater), vibration still there.

So, just pulled the tranny and confirmed the flex plate and hub were installed correctly with the roll pin, and yes they were. Ran the engine without TC and trans, vibration is gone. Did note there is only one way the TC bolts up due to the bolt pattern.

So now I'm left to the trans causing the vibration, but I'm as dumb as they come to transmissions so is this even an possibility? Once again, any advice here is welcome. Thanks!
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Old 02-22-2020, 07:48 PM   #10
1975IH200
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Default Re: Need Help Shaking out a Vibration

How about posting photos of the parts you are using to attach the TC and the flex plate???

There is a spacer on the front side of the flex plate....AND there is a Reinforcement Ring on the aft side of the flex plate, installed prior to installing the TC.

Do you have BOTH installed?
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Old 02-22-2020, 08:00 PM   #11
gainey261
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Default Re: Need Help Shaking out a Vibration

I'll take some pics and post, but yes I have both the hub and reinforcement ring installed.

I buried it in the last post, but with the TC amd trans out there is no vibration, all gone.

So I'm wondering (don't really trust the work the trans guy did for other reasons) could it be something on the input shaft of the trans causing this since the vibration is present even in park or gear. Or would it be more likely bad luck with TC number 2?
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Old 02-22-2020, 10:12 PM   #12
1975IH200
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Default Re: Need Help Shaking out a Vibration

I think your issue is with the flex plate attachment and/or the torque converter attachment.
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Old 02-23-2020, 03:57 AM   #13
Winchested
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Default Re: Need Help Shaking out a Vibration

Do you have the alignment hollow dowels installed on the engine? There are supposed to be 2 alignment hollow dowels that fit in the engine, they align the bellhousing. Same size pins that the heads use for alignment.
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