Driveline popping/binding sound with video

[jwnaron]

Hello,

I hope this is an acceptable use of this forum, but I have just picked up a 1979 Jeep CJ7 with AMC 258 i6 / 4.2l 6 cyl, THM400, quadra-trac Transfer Case and AMC20 rear axle. I bought this jeep this way and I am trying to diagnose a popping sound I have in the drivetrain.

Usually this issue happens when under a load, but the load doesn't have to be very large. I can induce this issue on jack stands by holding down the brake. The drivetrain is quiet when coasting and not under a load, but when accelerating I get this popping sound.

I can see the rear diff moving and see the effects of the popping in the rear springs, but I took off the diff. cover and all the teeth look good and don't think it's a diff issue. When I roll the tires manually the diff is quiet, no metal in the oil, so I don't think this is a diff issue but wanted to get you guy's opinion.

btw I think this is my first post on the forum, so I hope to be on here more in the future.

I apologize for the size of the video at 265MB, but hopefully this gives you an idea of the issue. And yeah I know I crappy videographer. If this video is just too all over the place i can take the skid plate off and take another video.

Here is a link to the video on dropbox:
https://dl.dropboxusercontent.com/u/25526468/GOPR9922.avi

 

[tarry99]

Angle of the drive lines and how that effects the U-joints ability to rotate at various angles.........Have you tried greasing these joints? May be dry?

 

[jwnaron]

I thought about it being something simple like that, but the noise doesn't seem to correlate to the spinning of the driveshaft. Meaning, that the driveshaft seems to spin smoothly and there isn't any play, but I guess it wouldn't hurt.

The way the differential pops and jumps and the rear springs flex made me thing it was something in the rear end, but I can't find even the slightest bit of wear in the rear end and it spins freely without excessive play and is silent as I spin the driveshaft by hand.

Thank you for your response. I think I'm going to drop the skip plate here in a minute and see if I can see anything else. I'll post a link to another video.

I really don't want to remove the Transfer Case and/or Transmission without some sort of proof that that's the problem.

Some background...

**A milemarker 2 by 4 conversion was done to the Transfer Case .
**Rugged Ridge one-piece axles have been put in the rear axle
**a SHIFT shift kit was put into the THM400 (The 400 Kit with Separator Plate)

As far as I know everything worked fine after it was all installed.

 

[Lumpy Grits]

Grease the u-joints and slip spline. Make sure the drive shaft 'clocking' of the u-joints is correct. They must be 90* to each other.
Can you feel any play in the u-joints? ANY PLAY is too much.
With your Q-track, I would say the noise is most likely coming from the chain in the t'case
Get a wrench on every bolt you can under there. Also ck your tranny mount for issues.
LG

 

[Peanut Butter]

I would definitely check the chain in your QT TC. These chains are neglected all the time. The slop in the chain could cause a lot of problems. There is a square pipe plug on the bottom of the TC. Remove it, catch the oil, and push a screw driver against the chain. Measure the amount of travel the screwdriver goes into the TC. Anything over 1/2" is bad. 1/4" to 1/2" means you're going to need to replace that chain soon. Add fresh automatic Transmission fluid back to you TC. If you need to replace the chain this is the only USA manufactured chain available: QuadraTrac BW1339-BW1305 Parts It is a most likely a cheap China made chain was used in the change over from the OEM parts to the part-time parts. There are several good articles out there on the QT TC. A Google search should work. Also make sure your vacuum switch is functioning properly. A bad vacuum hose can cause the TC to be locked in when it shouldn't be.

 

[jwnaron]

Grease the u-joints and slip spline. Make sure the drive shaft 'clocking' of the u-joints is correct. They must be 90* to each other.
Can you feel any play in the u-joints? ANY PLAY is too much.
With your Q-track, I would say the noise is most likely coming from the chain in the t'case
Get a wrench on every bolt you can under there. Also ck your tranny mount for issues.
LG

Thank you LG. There is no play in u-joints or anywhere I can find in the shaft. The pinion angle looks correct to me. The differential pinion is parallel with the output shaft on the Transfer Case , so I think that is the correct orientation and results in the angles of the driveshaft where the ujoints are located to appear to be at inverse angles (the same angle just in the opposite directions). The tranny mount, maybe the is the Transfer Case mount, that is directly on top of the skid plate looks to be a new red colored mount. I can't see any movement when the popping occurs. I will double check bolts.

 

[jwnaron]

I would definitely check the chain in your QT TC. These chains are neglected all the time. The slop in the chain could cause a lot of problems. There is a square pipe plug on the bottom of the TC. Remove it, catch the oil, and push a screw driver against the chain. Measure the amount of travel the screwdriver goes into the TC. Anything over 1/2" is bad. 1/4" to 1/2" means you're going to need to replace that chain soon. Add fresh automatic Transmission fluid back to you TC. If you need to replace the chain this is the only USA manufactured chain available: QuadraTrac BW1339-BW1305 Parts It is a most likely a cheap China made chain was used in the change over from the OEM parts to the part-time parts. There are several good articles out there on the QT TC. A Google search should work. Also make sure your vacuum switch is functioning properly. A bad vacuum hose can cause the TC to be locked in when it shouldn't be.

Thank you PB! I am starting to lean towards the Transfer Case as well. Dang I just wish I could get some proof before I take that thing out. I will check the chain play as you described and report back. I did notice the vacuum hoses and they appear to be in good condition. The front driveshaft isn't turning, so I think would indicate that it is not locked in 4-wheel drive. Thanks again for the help PB and everyone else that has chimed in. I'll update the thread once I check the TC chain play.

 

[Lumpy Grits]

How many miles on the t'case chain that in there now?
FWIW: I too lean towards the chain being the issue now.
LG

 

[Peanut Butter]

I would definitely check the chain in your QT TC. These chains are neglected all the time. The slop in the chain could cause a lot of problems. There is a square pipe plug on the bottom of the TC. Remove it, catch the oil, and push a screw driver against the chain. Measure the amount of travel the screwdriver goes into the TC. Anything over 1/2" is bad. 1/4" to 1/2" means you're going to need to replace that chain soon. Add fresh automatic Transmission fluid back to you TC. If you need to replace the chain this is the only USA manufactured chain available: QuadraTrac BW1339-BW1305 Parts It is a most likely a cheap China made chain was used in the change over from the OEM parts to the part-time parts. There are several good articles out there on the QT TC. A Google search should work. Also make sure your vacuum switch is functioning properly. A bad vacuum hose can cause the TC to be locked in when it shouldn't be.

Thank you PB! I am starting to lean towards the Transfer Case as well. Dang I just wish I could get some proof before I take that thing out. I will check the chain play as you described and report back. I did notice the vacuum hoses and they appear to be in good condition. The front driveshaft isn't turning, so I think would indicate that it is not locked in 4-wheel drive. Thanks again for the help PB and everyone else that has chimed in. I'll update the thread once I check the TC chain play.

.

Good sign that the front drive shaft is not moving. That means it is not locked. You should also have lock out hubs that are not locked. But the chain in the TC is always moving to power the rear wheels. If it is and most likely it is a cheep china chain, they are easy to replace. BJ's is the ONLY place to buy a chain. The chain can be replaced without removing the entire TC. You will only need to take the back half off. Let me know if you need anymore help. I just rebuilt mine. You can see some pictures in my build link below.

 

[jwnaron]

LG: The PO says that prob 10k miles since the Transmission was done (shift kit is all that was done as far as I know) and 20k since the TC was converted, but he says it has been repaired since the original conversion was done. He says it could be less that those numbers, but that's a good rough estimate. The odometer says 29k so I'm guessing that's 129k miles on it total.

PB: Yeah there are manual hubs in the front that are not locked, correct.

So what do you guys think about replacing the QT TC? I just so happen to have a SM465 Transmission bolted to a Dana 300 out of an 80s CJ. I like the THM400 and for a less experienced driver I think I like the convenience of the auto. If I swapped out the TC for the Dana 300 am I looking at replacing the rear axle? It looks like the output shaft for the TCs are on different sides and the AMC20 rear is offset I think to match the QT TC. Not necessarily looking at swapping the rear axle yet. I just really want to get it rolling and driveable so I can do fun stuff like suspension, etc.

 

[Lumpy Grits]

You have an offset rear axle that was made that way just for the QT.
If you swap that, then go to the SM465 if that's truly what you want.
ME-I'd buy a quality chain, and be done with it.....
LG

 

[Peanut Butter]

The QT TC is a great TC if it is properly maintained and good USA parts are used, don't sell it short. It was the first TC to be chain driven, which led to many more such TC. When you talk about swapping stuff you're talking $$$. Just keep that in mind. The Dana 300 is an awesome TC. Changing the rear end may get expensive. You've got to consider width and gear ratio to match the front. There will need to be different Transmission and TC mounts. If you go to a Standard Transmission . you will need the entire shift linkage. Add up the dollars to do that and then compare them to an adapter kit form Advanced or Novak. Novak also has a really good tech page on everything. The choices are hard and only you can decide what's best for you. First make sure of what the problem is before making any changes. If it is the chain, BJ's chain is only a $250 investment to get it back running. The chains from everybody else last 10 to 15k. BJ's should go 25 to 30K easy. Here is a good site for some QT info: Jeep QuadraTrac

 

[jwnaron]

Thanks for the responses. I don't think I want to get into the Dana 300 swap. I'd rather just get it running properly and get on with getting out and wheelin' it versus having a garage toy. It might be a couple of days before I can work on the TC, but I'm going to drain the TC and check the chain tension as the next step in troubleshooting and I'll report back.

 

[Lumpy Grits]

Good plan-Spend the extra for the good chain.
LG

 

[jwnaron]

So I just wanted to update this thread in case anyone is curious what I found. I checked the chain tension and I measured 1.25" and probably could have stretched it to 1.4" , so it looks like at the very least this needs to be replaced.

I'm not sure if I should just replace the chain with the Transfer Case still in the jeep, or should I just use this as an opportunity to go through the whole Transfer Case . I'm a little worried about potential damage the slipping chain could have caused to the gears, but I guess I'll see the gears either way regardless whether I take the Transfer Case out or not.

I was reading about the stick-slip condition that occurs on stock transfer cases during a turn when the wheels are turning at different rates. There was a mention in the TSM that if you hear the stick-slip sound (which was described very similar to my sound) but it happens when driving in a straight line and a louder noise then check the chain tension.

So, if you guys have opinions of whether to just put a chain on it and be done with it or pull the whole Transfer Case out and go through the whole thing I'd like to hear opinions, especially from anyone that has already done the QT chain replacement.

Thanks.

 

[Lumpy Grits]

Baby steps
See what a quality chain does, and go from there.
Make sure you use the CORRECT, ATF fluid.
LG

 

[jwnaron]

well you know what's coming next right?

What is the correct type? Dextron? I'm guessing I don't have to use that special QT fluid anymore since it has the 2 by 4 conversion?

 

[jwnaron]

The milemarker instructions for the conversion say standard ATF automatic fluid, so sounds like regular Dextron that I use in the THM400 should work I'm assuming.

 

[Lumpy Grits]

IIRC-PLEASE VERIFY. Dexron/Mercon was the correct ATF.
LG

 

[mstar]

LG, I am not a expert on the QT setup.do they use a simple 2 u-joint system or a double cardan in front or ? Are you saying the yokes should oppose each other 90* I have done it different is why I am asking