Alright gents, here's what I found last night. I'm still a skeptic on it being the trans (even though that's the last thing I changed, so logically that's the problem) so I pulled the motor mounts and replaced them last night. Started it up to check the timing and that comes in just fine, set at 10 BTDC initial with a total of about 38. Here's the kicker though, while I was outside the car running the motor, bringing it up to speed to check the timing, I noticed not a damn thing! So I played with that for a minute or two, revving and idling the engine, brought it up to about 5k and through all the ranges, no problems. Smooth as a baby's ****. So I hopped in the car to try the same thing, and I get a vibration. This is all sitting in neutral in the driveway, but is leading me to the conclusion that there is a harmonic issue between the components, brought to light, or caused, as the case may be, by the new trans mount and crossmember, which are somewhat less forgiving than the previous ones, possibly leading into the harmonic issue. So that's where I'm at, now I need to figure out how to get rid of it.
What about the coil? I've chased a similar problem and found the coil to be bad. Check it out or swap it.
Okay, we are getting somewhere, you have had the problem all along, but the softer mounts were masking it - maybe your *** is too sensitive? So we have determined that it is in the motor and it does it in neutral and with the clutch in - but wait, perhaps the pressure plate is out of balance? Maybe something broke in the motor you are not aware of yet? Is that the same flywheel you had balanced with the crank? Keep poking, you will find it.
So now we find the swapped trans is not "the only thing" new or different to the equation , but also a new trans mount and and crossmember were added. The logic needs to include ALL of the new or changed items immediately before the new problem shows up. Sure it could be the trans, but now it could be the mount, the crossmember, the frame, the mounting of those, too much rigidity, not enough rigidity, new or relocated stress at the engine mount bolts if you went up or down on trans tail... Highly possible the problem was there before and not new at all. This goes back to balance issues. All BS aside, if it really was fine before you did a trans swap & now it's not . then it's related to something you did during the swap or parts you used during the swap. Only you know what you did. A trans crossmember is a major component of the equation. Then again, it could have been screwed up from the get go. I hope you solve your issue and get back to enjoying your hot rod.
Here's a little story you may find amusing. It goes with the general theme of this thread new problem/ go back to the last thing you did but involves a motorcycle , 1979 Harley flh. If you know how Harley's are designed to go together, you'll get this. Ok so this flh runs great but has a strange vibration In 3rd gear but I buy it anyway cause its dirt cheap. Why it was so cheap will become apparent. But the bike was all redone, beautiful and fresh. The PO stated that upon re***embly the vibration was there and he couldn't get rid of it. I redid the engine transmission alignment procedure and no change. Started chacing the moving components in the primary. Compensating sprocket, clutch basket, primary chain swapping in known good used parts. No change and actually getting worse. Picked the brains of some certified Harley mechanics and it boiled down to trans alignment again. So I paid a custom bike shop to redo the alignment again, just incase I might have done something wrong. Well no change in the vibration. There conclusion was that something might be machined wrong with the mating surfaces or bent frame ! Bent frame and fresh rebuild on the bike make sense, accident / fix and flip . Bingo. Strip bike and have frame checked for straightness and being bent. Nothing found wrong with the frame. **** me cause this bike isn't cheap anymore. After about 1500 miles the vibration is no longer tolerable and has gotten progressively worse with every mile and every attempt to correct it hasn't worked. Now I need to have the trans rebuilt. Some bartering with by buddy and we found 3rd gear shot and a few other parts screwy in there from wear. My buddy says its from trans alignment and that's what caused the trans to eat itself. So we start checking stuff and he suggests a new inner primary to be sure. The old one was repaired and maybe something was off even though it checked perfectly. Well I get the new inner primary, and brand new compensating sprocket and clutch basket and primary chain. I also had him put it together because I'd trust him with my life. Pick the bike up and Now the problem is gone finally whoo-hoo!!! This lasted about 5 miles and it faintly started again. Now I'm pissed off so I get a brand new trans. Chrome with a kicker too. Tear it apart and put the new trans in. Perfect !!! Yep for about 5 miles. Well it can't be the trans. It's been aligned 47 times by different guys with a combined experience of 4 centuries so its not that. It's not the moving components. It's not the frame or the primary, or engine case. Now what ??? Rear maybe, harmonics of the rear chain ? Possible. Spring loaded chain dampener nice but still sort of faint on the new trans. Well lets try a Die spring on the primary chain adjuster. Ohhh real pita but very nice. Whoo hoo vibrations gone!!!! Yeap that lasted about 100 miles and I could feel it again. Well **** it, I'll put belt drive on my shovel. Major bucks but man it was smooth. Dry clutch too more $$$ I got about 400 miles on it and it shredded the primary belt, looked like chicken feathers and that was at Daytona. **** meeee running. Ok now what ? This bike certainly isn't cheap anymore. **** it ill get a new bike!!! Now I had two bikes- one to ride and ill be damned at this point if ill not find the problem with the shovel. And you know what, I have enough spare parts now to get a good jump at building another. While searching for a blow up of an obscure part for the bike I was building I stumbled across a small footnote for 1979 trans bolts. The mounting plate bolts are a bit different and a special bolt is required. It looked to be drawn as simple carriage bolt with one side of the round removed. Oh could this be the problem with the vibrating shovel ??? Special ordered the bolts ,,,, $2.79 each. Couldn't wait till they showed up but was skeptical at the same time. When I had them in my hand they were exactly as I thought, a carriage bolt that was flat spotted to the shank. So I took the shovel apart. Removed the belt drive, took the parts off the shelf and put the bike back together with the $2.79 x2 trans plate bolts. Absolutely perfect !!!! Now the moral of the story is that the subs***ution of these two bolts caused the issue. 400 years worth of experience missed it. I did call the guy I bought it from and he specifically remembers throwing those ground up bolts in his bolt bucket. But at the same time said he didn't change anything and put the perfect before rebuild bike back together exactly as it was taken apart.
This I do find amusing! But I sympathize. I'm headed that direction right about now. For the sake of troubleshooting, I'm on the route to removing pieces one by one to figure out just which one has the issue. First up: trans crossmember. Mostly because it's easier.
Before you get into the hard work, I want to relate a story from my younger days. Friend had a '64 Galaxie with 289. It developed a rough running range just above idle, say 1200-1800 rpm, under light load. After messing around with it a good bit to no avail, it was revealed that he had bumped the timing up to get snappier perfromance off the line. Disconnected the vacuum advance hose and it settled right back into baby-**** smooth running. Apparently the high initial lead plus the vacuum advance was too much timing for lower speeds. We were too dumb to realize that the vacuum advance was adjustable, so the fix was to return the timing to the factory recommended setting. BTW, my failing memory recalls factory recommended timing as being 6-8 btdc, not 10-14. So if you have vacuum advance, try it with the hose disconnected and plugged. I have no explanation for the sudden appearance of your problem other than new heads produced better vacuum or vacuum advance spring decided to take a dump. Good luck.
Here's another one as told to me by my Dad. If you check my profile you'll find out a bit more about him. In the very late 60s my dads life long friend and who was also a mechanic had a 283 powered land yacht that was running rough. My dad was ribbing him about his procrastination of doing a tune up on it. Turns out he just completed a tune up and it was actually worse. It wasnt running good before the tune up and barely running after. Well my dads friend was frustrated and started chasing ghosts. Distributor- same carb-same valve springs - same timing chain- same and right into a complete loss and tizzy because everything he tried resulted the same. He wound up doing a complete rebuild of the engine. Upon re installation the same damn **** barely running -same. So these two have a pow-wow and mutual brain picking session over a few beers at the bar. Kind of like we do here. He runs thru a laundry list of cam specs, piston size, ring gaps, specs, and general ********. My dad asks him about the car before his rebuild. His buddy scoffed and says it doesn't matter because its all new stuff. My dad keeps on the prior to rebuild state of the engine. Well after they are both 1/2 drunk my dad finally gets his answers. The car ran great, always ran great, and it was time for routine tune up but He put it off for a while. Then one day he did the general tune up, plugs,wires, points, condenser, cap, rotor, blah blah blah. So my dad says well, look at everything you did right before it got worse. He says "******** it's all new rebuild now" Some general banter and a wager was struck. $22.00 because that's all my dad had in his pocket that he'd fix the car in the dark in the parking lot right there. Catch is his buddy had to hold the flashlight. My dad opens the hood of his own car and strips the plug wires off of his own car. His buddy is laughing thinking he's so drunk he's working on the wrong car. So then he opens the hood of the guys Chevy and swapped the wires from his car to his buddies. "Ok start it up" my dad tells him. Vroom purring like a kitten almost. Couple tweaks on the carb screws and its about perfect. Right about then my dad asks if his buddy would like to bet 44.00 that his car would run like **** if he installed the Chevy wires back onto his car? Turns out that with every step or change done to the Chevy those new wires were used. Problem is that they were bad. Change distributor & bad wires no change. Change carb and bad wires no change, rebuild engine and use the same bad wires because they are new and no change. So moral of the story new parts aren't always good and when a new problem shows up go back to the last thing you did. No matter how silly it might seem. Don't chase ghosts
Every time I have had a problem in roughly the rpm range you are describing, it has turned out to be in the carb enrichment circuits. --- Steve ---
I haven't had a chance to work on it again, but I have noticed a couple things. One: when I'm in first gear and load it up (i.e. let off the clutch a bit but keep the foot on the brake) I notice a tapping sound, leading me to believe the trans is hitting the tunnel somewhere. Also, when driving it has a similar sound occasionally. I'm definitely of the mind that it is the transmission installation (as logic would dictate in the first place...) and plan to pull it out as soon as I can to check it. If not tonight, hopefully over the weekend.
So I had a chance to work on my ride over the weekend, and here's what I did: I pulled the trans and ran the car without it. Turns out the engine is running fine (as I had come to suspect...). So I pulled the T5 apart, as well as the old one, swapped the input shafts, and noticed that a small spacer was missing out of the trans that I had just put in! Well, not wanting to chance that being the only issue, I repaired the forks on the old transmission and put that one back in. I also noticed that there was a little wear on the trans tunnel, probably from where the trans had been rubbing, so I clearanced that too. Long story short, definitely wasn't the engine, it was the new trans mount/crossmember and the missing spacer (I think). Runs good now!
creepy, I am going thru the same thing................with the 55 Ford. I bought the car for my son, from an Old Cat who had had a stroke and could not talk well. I really couldn't understand anything he said, and neither could his grandson who was trying to interpret... he kept trying to tell me something about the "brand new" rebuilt transmission...he had installed...that it needed some $10 part, or it vibrated... or??? I COULDN"T UNDERSTAND THE MAN! so now that all makes some sense.. as it does the very thing you have described in your post....runs great..289,auto,.... Lets check out the Transmission...? Thanks Boryca for the post and to everyone that chipped in their 2 cents....especially Vicky31 for his common sense detective work..........
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