Ok, I apologize if this isn't the right place for this. So, this chain of events has been going on for awhile and has 3 mechanics and a transmission shop stumped. Car - 52 styleline deluxe 4dr Engine - crate gm performance shop h.o.350 Trans - B&M th350 Differential - 56 chevy del ray Driveshaft - custom made to length through speedway motors. Car has been running and driving fine since initial build. Plenty of power for what i want. Transmission was bought used, so unknown history on it. One day driving down the highway i noticed what sounded like a "grinding" noise from the drivetrain when i would ease up on the gas and just try to maintain cruising speed of 55ish mph. Thought to myself, "great, time to rebuild the rear end" as i knew where it came from and it was next on list of getting a rebuild anyways. Put it in the shop, order complete new richmond 3.55 gear set up for it, all new seals, bearings, completely new from wheel hub to wheel hub. Go for a test ride, no joy. Noise still there. So then we all started wondering what the hell it could be. Thought, well, we dont know the full history of the trans, so might as well. I have a friend that runs a big transmission shop and has done me right in the past, so i trailered her up to him. Told him to go through it and upgrade the weak points and whatever he saw fit. A new tci 2200 stall was also installed at this time as well. Pick it up a few days later, he said the only things he found wrong internally was a couple of smoked clutches, but all line pressures etc read perfect. He said he put better sprag and couple other parts in it but it was in overall great shape inside, didnt notice anything broke etc.. Hop in it, drive it 50 miles home, once up to highway speeds....same thing. Gindish noise is still the at light load/ barely in throttle to just maintain speed. Get home, call him and tell him whats up and it is still being weird, so trailer it back up to him, he drops pan, checks things out for a couple days and says he cant find anything that points to transmission. Said if something was internally binding or wrong it would have never made it home. Car shifts fine, nothing seems off about the operation of the trans. So here we are. Still has a funky "grinding" noise at light load barely on the throttle. If you accelerate it goes away, if you let totally off the gas it goes away. Its only at one particular spot it does it and its unfortunately right where you cruise to maintain speed, so highly annoying. Have checked exhaust, seems to have plenty of room everywhere and not into anything, driveshaft is tight, everything is greased, crossmembers are tight. Nothing at all looks out of place. Soo here I am, asking the help of the all knowing h.a.m.b. Can anyone help a junior hot rodder out?
Crank pulley rubbing, something coming into contact with the driveshaft, inner lip of a front wheel rubbing the lower control arm or brake caliper..... sounds like it's getting better, just keep driving, it'll clearance itself.
Hey, thanks for the replies. Ebrake was deleted in the v8 swap. Nothing touching shaft at all. No clutch fan, straight old mechanical with electric pushers.
Probably only a million possibilities but it kinda sounds like maybe something grounding out. A bushing, exhaust, trans mount or something of that nature.
Did your buddy inspect the flexplate closely? Cracks can make a noise similar to what you describe, and the behavior of it going away and coming back with load is another symptom. Here's an example.
Noises like this can be tough to diagnose with the car in front of you, but I’ll throw my hat into the ring. I’ll start with the most likely first. 1-What condition are the engine mounts in? 2-What condition are the transmission mounts in? 3-Certainly the engine mounts are NOT of the solid type? 4-What type of throttle linkage is being used? I’ve seen rod and pivot type (mechanically solid, non cable type) linkages transmit NVH (Noise, Vibration, Harshness) directly into the cabin of the car, or truck. 5-What condition are your rear leaf spring eye bushings in? NVH can start in the rear and travel right up the driveshaft and fool you into thinking it’s coming from someplace else. 5-What kind of shifter and linkage are you using? Same idea, worn out or missing bushings will transmit the NVH right into the cabin if using a solid type linkage. Good Luck, and happy hunting, please keep us informed. Andy
Should of heard the one in my girlfriends 56. The grinding sound was so load when it happened she freaked out. I was right beside her when she was driving.
Nothing touching or rubbing anywhere on engine or chassis. Engine mounts are brand new, trans mounts are brand new, car has been converted to late model leaf spring, all brand new bushings, hangers, new leaf pack, etc.. new shocks all around, shifter is brand new lokar. Everything about this car mechanically and electrically is new. No o.g. parts were reused.
Gotas, that is real similar sounding although the trans guy said he checked the flexplate. Sounds like that under a light load and will quieten down with more throttle or get out of throttle
U joints were inspected when rear end was done. They were installed new with drive shaft about 600 miles ago.
Lol, i told yall this is a good one. Everything is new about this build, car currently has 6xx miles on it since complete and one day just started making stupid noise.
Might be the pulleys up front..... they might be rubbing on something.... Then again, what do I know..?
Could it be the muffler bearing ? Seriously, torque converter inspection cover. Speedo cable Flex plate Bearing in the transmission Pinion bearing could it be exhaust grounding out ? I’ve heard similar noises on cars with hangar bearings or when pinion bearings go. real hard when your not in from of it listening. Will it make the noise up on a hoist or only driving down the road ?
Will try to adjust angles on the driveshaft. Will make noise in air and on road. Am also thinking i may have to check out the flexplate as well.
Since it will make the noise in air and on ground, I assume you can recreate the noise while the car is on a hoist? Does the noise change pitch or sound different between being on the road or in the air? Does the car have to be in gear to make the noise, or will it make the noise just by revving the motor to a specific rpm range without the transmission involved with the process? Can the noise be made on the hoist with someone listening for its possible location from under the lifted car? I've seen where exhaust can make some pretty strange noises at different rpm, a broken or cracked baffle in a muffler can produce a grinding noise as it shifts inside the muffler housing. Gene
I've never had a car with one, but I've read guys on here who had noisy Lokar shifters. The detent cable in the middle vibrates in the shaft.
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