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New 1st Gen Owner, trans "thumping" issue/question
1st Gen. Ram - All TopicsDiscussion for all Dodge Rams prior to 1994. This includes engine, drivetrain and non-drivetrain discussions. Anything prior to 1994 should go in here.
New 1st Gen Owner, trans "thumping" issue/question
Hello! I'm a new 1st gen owner and have spent weeks reading different threads, what a great resource! Truly appreciate everyone's content... tons of information (I hope I am able to contribute as much as some of you over the years)!!! I've been wanting a 1st gen for years, and finally pulled the trigger on a 1993 D250. The details are in my signature, but in short, it's a stock 1993 with the NV4500, 1/8 timing bump, rotated fuel pin, and 1 turn on the power screw (all done by previous owner). Right now it's sitting at 188k miles... zero rust, original paint in great shape, man I love this truck. Just installed tach, boost, and pyro gauges (felt like I was driving blind coming off my 2014 GMC, lol).
So I started noticing an issue, and after searching/reading 100's of posts, I'm reaching out for some feedback.
When parked with the truck in neutral there is a loud "thumping" noise that you can feel in the floor boards, steering wheel, and pedals. If I disengage the clutch it gets less/changes. Likewise, you can hear/feel the "thump" while driving... it's most noticeable in 3rd, 4th, and 5th gears and get's faster/slower with RPM change (most noticeable between 1100 and 16-1700 RPM). It sounds/feels more like a vibration when you get over 16-1700 RPMS. I've struggled to describe the noise in my searches... but a "thump thump thump" that you can hear and feel is about as close as I can get. Kind of sounds like an air compressor pumping up... but more defined and a little louder.
I cannot hear the noise from under the hood or under the truck... I can only hear/feel it in the cab. My gut says it's coming from the transmission/bell housing area, but that's just a guess at this point. The engine purrs, no missing. I don't know a ton about the history on this truck, other that it appears to have been really well taken care of. The PO indicated that within the last 5000k all fluids were serviced and the rear main seal was replaced. The suspension/steering is tight and wheel bearings are all good.
I'd appreciate any feedback/thoughts or where to start looking. Thanks in advance! (will post some pics of this beauty soon!!).
Last edited by roadog; 12-21-2018 at 07:18 AM.
Reason: Additional information
If you have access to a lift it might be useful to get it up in the air and have someone put it in gear and see what you can see. Driveshaft out of whack making contact with something, bad u-joint etc. I bought a 1st gen motor plate that had some galling around the interior perimeter like the flex plate had made contact with it at some point. I guess that could happen if something became extremely loose. Lots of super smart dodge guys on here. One of them will probably get you fixed up. Good luck.
Welcome to the forum, it sounds to me like something is touching the cab, like a bolt backed out of the bell housing, or a broken motor or tranny mount. Chock the tires, leave it running in neutral and use your phones camera to look around the tranny bell housing area up top to see if anything is touching the firewall or floorboards.
Welcome to the forum, it sounds to me like something is touching the cab, like a bolt backed out of the bell housing, or a broken motor or tranny mount. Chock the tires, leave it running in neutral and use your phones camera to look around the tranny bell housing area up top to see if anything is touching the firewall or floorboards.
Good idea... will do. Ill check it out this afternoon. Thanks!
Sorry for the delay!!! I was able to get under there and snoop around...
There doesn't seem to be an inspection plate, so without unbolting the trans I don't think Ill be able to inspect anything internally. And although I'm confident I could figure it out, I will probably wait until someone with a little more experience can assist!
I looked all around the transmission/bell housing... all the bolts were tight and nothing is touching the cab/tunnel, etc.
My U-joints are in great shape... as are my engine mounts. The transmission mount is a little funky, but I'm assuming this is status quo for a NV4500 swap. I took some pics of it... It's a steel plate with a couple rubber bushings.
I did notice something that I wanted to share... the down tube of the exhaust comes off the turbo and has a bracket that is attached to the bell housing with one of the bolts... it has a rubber donut that the bolt goes through. It looks like the bracket is grinding into the bell housing a bit.. you should be able to see this in the pics. Not sure if this plays into it... but thought I would mention it.
A couple points to make that I noticed in the last couple of days... You CAN NOT feel this "thump" in the shifter at idle, in gear, or driving. Also, I stated above that if you disengage the clutch it goes away... well that is sometimes true and sometimes not true. I've since noticed that sometimes disengaging the clutch does not stop the noise... It does have an effect on it, but doesn't always make it go away.
Appreciate everyone's help/feedback. Let me know what you think!
I'd like to compliment you on your writing skills.
Clear, concise, punctuation, and you actually know how to use the enter button to create paragraphs separating thoughts, vs one long, run-on sentence.
I would keep a ledger in the truck and notate everything possible. Road conditions, weather, speeds, cargo loaded or not, etc. This, ultimately will provide enough info to determine the cause.
BTW, I'm not a big fan of the downtube being bolted to the side of the transmission bellhousing. Mine broke completely off from the stress and weight of the exhaust on the bolt. I've relocated a new, heavy duty mount where it's bolted (with reinforcing plates) through my floor, just below the heater box. Granted, it's a bigger, 4" system I have on my truck, but the new mount location removes the stress from the system, from the single, little bolt on the transmission. The bolt hole could not be saved, and eventually, I wound up damaging the hole in the adapter plate. There was no way of installing a helicoil on there, or using a conventional bolt to adapter plate scenario. I drilled out the adapter plate, and used a long through bolt that exits both through the bellhousing and the adapter plate. Works fine, but would have been unnecessary if the bolt hadn't sheared off in the first place.
Is it an optical illusion or is the transmission mount really close to the cross member? Is it possible that it is moving enough to knock on the cross member? You might need some new bushings there. On mine, which is slightly retrofitted, I may have to trim the trans mount on mine to prevent it from contacting the crossmember. You might be able to wiggle the trans around by hand and see if its making contact. Good luck and let us know.
I'd like to compliment you on your writing skills.
Clear, concise, punctuation, and you actually know how to use the enter button to create paragraphs separating thoughts, vs one long, run-on sentence.
I agree. Clear communication is such a rare thing these days. Its actually refreshing to read a post from someone that understands grammar and punctuation.
Anyways, I have had a lot of strange noises from loose exhaust vibrating on the frame rail and bellhousing. I have had to adjust my downpipe with a Ford wrench and ball peen hammer to make it clear on my '74 W200.
Also, I agree that you need to replace the transmission mounts and get that base plate away from the cross member.
When I had my G-360 replaced the rear mount was gone. I put in a new one and my thumping was gone. I had a clank when taking the slack out of the drive-line because all 3 U-Joints were bad. Thump is bad mount. Clank is bad U-Joints. I have another clank when I shut off the motor which is the exhaust pipe hitting somewhere. Eventually I'll either buy a muffler and re-position it or get a new 4" system.
Hope everyone had a great Christmas! Thanks so much for the replies.
Originally Posted by NJTman
I'd like to compliment you on your writing skills.
Clear, concise, punctuation, and you actually know how to use the enter button to create paragraphs separating thoughts, vs one long, run-on sentence.
I would keep a ledger in the truck and notate everything possible. Road conditions, weather, speeds, cargo loaded or not, etc. This, ultimately will provide enough info to determine the cause.
Merry Christmas to you and your family
Thanks! I try to keep it organized... lol. Trying to diagnose/understand an issue via a forum is hard enough, then throw in a bunch of ramblings, it makes it hard!
Originally Posted by NJTman
BTW, I'm not a big fan of the downtube being bolted to the side of the transmission bellhousing. Mine broke completely off from the stress and weight of the exhaust on the bolt. I've relocated a new, heavy duty mount where it's bolted (with reinforcing plates) through my floor, just below the heater box. Granted, it's a bigger, 4" system I have on my truck, but the new mount location removes the stress from the system, from the single, little bolt on the transmission. The bolt hole could not be saved, and eventually, I wound up damaging the hole in the adapter plate. There was no way of installing a helicoil on there, or using a conventional bolt to adapter plate scenario. I drilled out the adapter plate, and used a long through bolt that exits both through the bellhousing and the adapter plate. Works fine, but would have been unnecessary if the bolt hadn't sheared off in the first place.
Others may disagree.
I agree... seems suspect to me as well. I'm going to remove and re-locate... If for no other reason than it looks risky to leave it the way it is. Thanks!
Originally Posted by 66fora69er
Is it an optical illusion or is the transmission mount really close to the cross member? Is it possible that it is moving enough to knock on the cross member? You might need some new bushings there. On mine, which is slightly retrofitted, I may have to trim the trans mount on mine to prevent it from contacting the crossmember. You might be able to wiggle the trans around by hand and see if its making contact. Good luck and let us know.
Merry Christmas All!
Thanks! I'm going to get back under there today and "push" on it a bit. I don't see any signs of that base plate coming in contact with the crossmember, but that doesn't mean it's not happening. I also agree that some new bushings/mount are in order.
Originally Posted by BHD
I agree. Clear communication is such a rare thing these days. Its actually refreshing to read a post from someone that understands grammar and punctuation.
Anyways, I have had a lot of strange noises from loose exhaust vibrating on the frame rail and bell-housing. I have had to adjust my downpipe with a Ford wrench and ball peen hammer to make it clear on my '74 W200.
Also, I agree that you need to replace the transmission mounts and get that base plate away from the cross member.
Keep us posted and welcome to the DTR.
Merry Christmas!
Thanks! Appreciate it. Is there a standard mount for these NV4500 conversions? I've snooped around a bit and am not seeing any pics showing the setup I have (steel plate, rubber bushings, and some doubled nuts, lol).
Originally Posted by edwinsmith
When I had my G-360 replaced the rear mount was gone. I put in a new one and my thumping was gone. I had a clank when taking the slack out of the drive-line because all 3 U-Joints were bad. Thump is bad mount. Clank is bad U-Joints. I have another clank when I shut off the motor which is the exhaust pipe hitting somewhere. Eventually I'll either buy a muffler and re-position it or get a new 4" system.
Edwin
This is good feedback on the the thumping... I am going to investigate that mount in more detail.
12-21-2018, 06:31 AM
