I was pretty spectacle on the brake rotors being the cause of this also, the symptom just dont match up. but the driveline is a definate concern of mine still. Today, while being in stand-still, stop n go traffic on the interstate i noticed that when in drive (C6 trans) and i slow to a crawl the transmission will drop down into first with a clunking, not-so-smooth action and cause a little jilt when it first goes into gear. but with any throttle opening at all will kick it back up into second and it works just fine, so i just kept it in 2nd gear the rest of the drive home (edit:until i was through the traffic jam, any speed above 10mph i put it back in drive). As for the i-beams, i wouldnt ever try to attempt any heating/bending of them anyway. just doesnt seem safe to temper and bend such a critical foundation. And i've been planning on aligning this truck since the day i got it. I have to hold the wheel about 25* left at all times to go straight so ive known its pretty far out. I'm gonna replace all the tie-rod ends and sleeves (if i can find them ) oreillys only carries the left outer tie rod end for a 2wd tein i-beam set up. I'll let yall know as i progress through this diagnosis. I have some questions about shock absorbers for the rear but i'll touch base on that when i get it on the lift and can take some decent pictures of my setup

 

As far as the clunking sound. Is it coming from the trans or the rear end? Mine clunks a little in the rear when u put in drive and when it drops into first as well. Check the backlash on ur gears. It should be between .008 and .010. Mine was a little loose when I checked it. I plan to fix this when I install my locker and 4.10 gears.

 

Also for the front end components try lmctruck.com or rockauto.com. One of those two places will have everything u need to rebuild the whole front end.

 

Ditto on LMC if you can't get stuff locally. Your Napa should be able to get everything, as they seem to be a lot better at older stuff.

I just had this kind of issue this past summer with my Mack truck. It had a "death wobble" to it that I couldn't pin down. I checked tie rods(with my hands) and they "seemed" okay. I rechecked them with a pry bar and block of wood and WOW...they were loose. Replaced them and presto-chango no more shake.

The clunking? As mentioned, could be rearend as the lash in the gearset gets worn it will bang around when loaded/unloaded. With parking brake set, in neutral, grab the rearend yoke and see how much it rotates back/forth? Likely that is the issue. If not, then grab Ujoints and check them for side/side movement.

BTW .008/.010 lash equates to barely any rotation at the yoke.

 

Thanks for the tip about napa. I have never thought to use them for any parts on this truck.

 

The clunking sound is coming from the trans. Ive spoken with my automatic transmission teacher and he agrees that the trans has 341,000 miles on it while towing a boat for 21 years that i should just overhaul it. i'm planning on contacting Monster Transmissions and getting an overhaul kit. also the planetary gear sets may still be good but ill probably get some replacements that change the initial and intermediate gear ratios. I still havent had time to get the truck on the lift as i've been working doubles and go to class full time. I'll post some updates here soon

 

Aahh that's sucks man. I'm sorry to hear that. Rebuilding a transmission can get expensive. You should just buy a new one that way you know your not useing old crap.

 

Monster transmissions sells overhaul kits for DIY. its basically everything they use to build their transmission (bands,servos,clutches,snap rings, seals, bushings, etc.) and you just rebuild using your existing case. Kind of like rebuilding your motor and using the same block. I'm going to see what my options are as far as converting to a lock-up clutch system so i'll get better fuel economy on the interstate. but i'll probably just opt for replacing the torque converter, valve body, planetary gears, and getting an overhaul kit. Ive planned on rebuilding it eventually but i guess ill start earlier on the drivetrain/suspension restoration than i expected.

 

Welp good luck. Iv rebuilt a few transmissions and you always find suprises. And with one that has over 300k miles I would look at everything real close