I am currently having an issue with my transmission, I believe. If you have time to check this video I would appreciate it. The truck is a 1978 k5 blazer with a sbc350 and a th350 turbo trans. It makes a single pop noise at certain speeds after warmed up (10 min of driving). It started when I was pulling a trailer. It would click upon immediate acceleration and kill the engine. Without towing it still clicks but usually at 30 and 50. I have replaced the modulator, and inspected the governor and accumulator; all appear fine. The transmission pan did have a gritty sludge layer at the bottom but nothing looked fresh. The fluid is pretty clean, but does have a slight burnt smell. Should I put a "trans fix fluid" to see if the clutch plates are worn, or does this sound more like a torque converter? Any help is appreciated.
CK5
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Click/Pop noise
- Thread starter CJ2
- Start date
I am currently having an issue with my transmission, I believe. If you have time to check this video I would appreciate it. The truck is a 1978 k5 blazer with a sbc350 and a th350 turbo trans. It makes a single pop noise at certain speeds after warmed up (10 min of driving). It started when I was pulling a trailer. It would click upon immediate acceleration and kill the engine. Without towing it still clicks but usually at 30 and 50. I have replaced the modulator, and inspected the governor and accumulator; all appear fine. The transmission pan did have a gritty sludge layer at the bottom but nothing looked fresh. The fluid is pretty clean, but does have a slight burnt smell. Should I put a "trans fix fluid" to see if the clutch plates are worn, or does this sound more like a torque converter? Any help is appreciated.
Are you talking about what happens at 8, 14, and 16 seconds? That sounds like a backfire to me, nothing else. Unburned fuel combusting in the exhaust.
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I had a similar problem on a small block mine turned out to be a bad distributor drive gear shaft.
I could see that. It is a weird noise. I thought it was trans because of the speed it would happen at. It likes to happen at speeds that the trans shifts at.
It is a very weird noise, but to me it sounded mechanical.
One thing to note is that the engine only has 40k miles on it. I also replaced the carburetor to a brand new one as I thought that was the source of the click some reason. What is weird to me is why it would happen at exact speeds like 50.
One thing to note is that the engine only has 40k miles on it. I also replaced the carburetor to a brand new one as I thought that was the source of the click some reason. What is weird to me is why it would happen at an exact speeds like 50. Also it takes 10 minutes of driving for it to start to do it.
Is the noise consistent at the same speeds every time?
Yes, that’s the noise. Don’t think it is a backfire though. I rev the engine in park and it sounds great. I can’t find anything similar on the internet about it.
It is usually. When driving it will happen at consistent speeds, but on another day it could be off give or take 5 mph. I did mess with the governor though. It always does it at 50 though. Sometimes at 30 to. Also, sometimes it won’t do it, but will come back in a few minutes. It happens during acceleration not when cruising at like 70. If I stay at 50 there will be several clicks back to back.
So hard to identify through video audio but if it turns out that it is not spark related then just to help eliminate any driveline possibilities I would start with inspecting the rear differential R&P as well as the carrier gears and center pin ( don’t forget the retention bolt - they are known to break but still be in place ).
The fact that it makes that noise more at a steady cruising speed where the driveline may load and unload as well as possible shift points makes careful inspection of the diff worthwhile.
got me thinking u joint, esp the 50 mph speed the drive line angle may just right to get a dry u joint to click
yeah with out the weight normally applied to the tires and axles it get sketchy at higher tire speeds
The problem with trying to duplicate the same conditions while on jack stands is that there is no “load” that creates the same type of rolling resistance ( applying the brakes lightly will not give the same effect ).
Wes’ thought on the u-joint inspection is definitely worth looking into.
As for your question on which diff to inspect that depends on if you still have a full-time setup with power going to each diff while on the road.
If so either axle could give that type of noise but starting with the rear is where the smart money is at.
Inspection is gonna require taking the diff cover off and actually verifying ever tooth on the R&P plus the pinion gears and side gears along with the center pin.
If things are really in bad shape you should see pieces and parts in the gear oil.
Taking the center pin and gears out will also help you visually inspect the pinion teeth once the case is empty.
Besides, it’s always a good excuse to change the gear oil if all is well.
Wes’ thought on the u-joint inspection is definitely worth looking into.
As for your question on which diff to inspect that depends on if you still have a full-time setup with power going to each diff while on the road.
If so either axle could give that type of noise but starting with the rear is where the smart money is at.
Inspection is gonna require taking the diff cover off and actually verifying ever tooth on the R&P plus the pinion gears and side gears along with the center pin.
If things are really in bad shape you should see pieces and parts in the gear oil.
Taking the center pin and gears out will also help you visually inspect the pinion teeth once the case is empty.
Besides, it’s always a good excuse to change the gear oil if all is well.
