Hey guys, I just recently did swap from a 318 to 360 behind a 904 trans in my 76 dart. I've been driving it around for about a week no problems, but recently I've been getting this vibration at 40mph or when the tranny shifts into second. It seems to get worse as I accelerate and it's almost like I'm driving over little speed bumps. It also goes away if I shift into neutral. Any ideas what this could be?
Transmission vibration?
- Thread starter Ashton
- Start date
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TrailBeast
AKA Mopars4us on Youtube
What does the trans fluid look and smell like?
Do you have the throttle pressure linkage hooked up and adjusted?
Do you have the throttle pressure linkage hooked up and adjusted?
If it just started I'll assume you have the right flex plate convertor combo. If it is more noticeable when you accelerate and is less when you let off. I would suspect a frozen/rusted front u-joint. Also make sure the rear u-joint is good and has the C clips on the two caps that mate to the yoke.
Yeah I bought the b&m flexplate when I swapped the motors. The tranny fluid is a bright red/pink kinda smells burned but its not a strong smell. I have the kick down connected connected. I don't know if its adjusted properly it seems to pull rod up when I push throttle all the way. And I've also been noticing hard shifts back into 1st when coming to a stop
Voeltagear
Well-Known Member
The hard shift is probably 3rd to 2nd. Around 15mph? Your throttle lever is set a little advanced. Meaning it is not returning to the full forward position when you let off the throttle. (I like this setting for a firmer shift and better clutch apply under light throttle.) Could be it needs a return spring or adjusting. With the throttle wide open the lever on the trans should just reach its rear most point. No resistance on the throttle rod. As for the vibration I have a similar problem. Have not been able to pin point but check your drive shaft length. should have 3/4 to 1 inch available slide into trans. Any more either way is too much. Could also be the gear setup in differential is not a match for the torque of the engine. example back lash is too tight or too loose. An experienced transmission/drive shaft shop should be able to help diagnose. As mentioned before check the u-joints for binding and proper centering. doesn't cost anything to take it out an check the joint vs diag time. PM me for more throttle rod adjusting questions.
PanGasket
has cork sides
Did you use the 318 converter behind the 360? If so. That's your problem. I saw your car on CL. Not bad for a four door.
66plyValiant
Well-Known Member
he used a balanced flex plate so its not the problem; I think voeltagear hit the head on the nail with the throttle pressure (kickdown) adjustment
TrailBeast
AKA Mopars4us on Youtube
An overadjusted TP linkage won't cause it to shudder or "feel like little speed bumps" but a bent driveline or ujoints can.
He also said it goes away if he puts it in neutral, so I have to go with ujoints with the info we currently have.
He also said it goes away if he puts it in neutral, so I have to go with ujoints with the info we currently have.
Voeltagear
Well-Known Member
my point about the throttle valve was in regards to the harsh downshift.
As for the vibration I agree with the driveshaft/u-joints. Check them first like I said before. A lot of posts on Mopar forums discuss possible causes for vibration in these cars. As for me, my Bro and I have 2 different setups both with similar vibrations. One is a 64 dart GT 360/904, 8 3/4 rear with 2.94 "highway" gears, headers dual exhaust with xpipe, 345hp/420ft/lb dyno at the rear wheels. the other is a 76 dart 2dr/hard top with a /6, 904, 8 1/4 rear with 3.23 "get this slug moving" gears, single exhaust probably 80 or so hp at the wheels. And the weird thing is the Vibes happen at the same vehicle speeds give or take. What I have noted that they do share is 2 door hard top design, 904 transmissions (one fresh and one OE 80k!), solid fans, neoprene bushing in the front, aftermarket replacement strut bushings (do not pop into hole like OE, starting to lean this way), unknown differential conditions (slight noise from both although the 8 3/4 is from a standard trans/HD truck- noise expected), some really poor body work from previous owners attempts to make them "look" good. So I have done a lot of testing and checking myself and no results yet. Hope to find a solution to share with everybody else in the same boat sooner than later. Start with the "free" testing and go from there. the better notes you take the more help the "Pro's" can give you at a lower cost. (being a auto tech i have experience with "unknown" problems that come in with no documentation about what has or hasn't been done). Hope this helps so we can all drive Vibration free Mopars one day!
As for the vibration I agree with the driveshaft/u-joints. Check them first like I said before. A lot of posts on Mopar forums discuss possible causes for vibration in these cars. As for me, my Bro and I have 2 different setups both with similar vibrations. One is a 64 dart GT 360/904, 8 3/4 rear with 2.94 "highway" gears, headers dual exhaust with xpipe, 345hp/420ft/lb dyno at the rear wheels. the other is a 76 dart 2dr/hard top with a /6, 904, 8 1/4 rear with 3.23 "get this slug moving" gears, single exhaust probably 80 or so hp at the wheels. And the weird thing is the Vibes happen at the same vehicle speeds give or take. What I have noted that they do share is 2 door hard top design, 904 transmissions (one fresh and one OE 80k!), solid fans, neoprene bushing in the front, aftermarket replacement strut bushings (do not pop into hole like OE, starting to lean this way), unknown differential conditions (slight noise from both although the 8 3/4 is from a standard trans/HD truck- noise expected), some really poor body work from previous owners attempts to make them "look" good. So I have done a lot of testing and checking myself and no results yet. Hope to find a solution to share with everybody else in the same boat sooner than later. Start with the "free" testing and go from there. the better notes you take the more help the "Pro's" can give you at a lower cost. (being a auto tech i have experience with "unknown" problems that come in with no documentation about what has or hasn't been done). Hope this helps so we can all drive Vibration free Mopars one day!
TrailBeast
AKA Mopars4us on Youtube
Understand completely, as I have been there and done that too.
Sure would be a lot easier if we could actually hear and feel the noises and vibrations wouldn't it?
Descriptions and the quality of sound on video's just doesn't help a lot most of the time.
Voeltagear
Well-Known Member
x2 Trailbeast
Thanks I get that alot driving around town when people hear it. It's a real sleeper.
Ill check ujoints here soon. I know they're original to car so they could be at fault here with the higher torque numbers from the 360. I don't know if this is useful or not but I have the 3.23 gears no posi and I'm pretty sure 7 1/4 rear end. Ill get around to upgrading it one day though!
PanGasket
has cork sides
Ashton. Your car most likely has the 8 1/4 rear. Its way too later after the deadline to have a 7 1/4 rearend. The 8 1/4 rear end it pretty strong. Its a pretty common upgrade from the 7 1/4 because it has BBP, is already A-body width and can take a beating from a very mild v8
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