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1991 F250 7.3 ZF 5, I've always had this odd noise when driving in 5th gear above 50 mph. It doesn't sound bad necessarily but its loud enough to hear in the cab through all the new sound proofing and shifter boot. The noise sounds like rotational static, similar to what static sounds like on a TV although not as harsh sounding and you can tell its coming from something spinning. It only happens in 5th gear, and gets louder with speed but not by much, since I bought the truck 3 years ago its probably gotten slightly louder although I can't be for certain. I've never heard it in 1-4 at any speed, the transmission is old but it looks like it was worked on before as the detent plugs have RTV on them. Should I be concerned with this noise or is normal?
try adding in an extra 1/2 quart, could be roll over noise and 5th is an OD gear
Harmonic balancer when they go.... will sound like a needle hammer in the trans when accelerating
I also had issue with 2 piece drive center shaft bearing do similar noises
Rear diff when a gear is going can sound like it as well.
If you have a sterling rear, can remove rear axles 4 inches out and pretend to drive it to isolate noises but dont try it in 4wd unless hubs are unlocked or it will move on you
try adding in an extra 1/2 quart, could be roll over noise and 5th is an OD gear
Harmonic balancer when they go.... will sound like a needle hammer in the trans when accelerating
I also had issue with 2 piece drive center shaft bearing do similar noises
Rear diff when a gear is going can sound like it as well.
If you have a sterling rear, can remove rear axles 4 inches out and pretend to drive it to isolate noises but dont try it in 4wd unless hubs are unlocked or it will move on you
I run an extra quart of fluid in the transmission to help with rollover. I did replace all u joints and the carrier bearing a year ago but I'll check it. I just did a diff fluid change and while dirty the gear looked basically new with no weird pattern. The spider gears did look like they have seen some miles though. I don't believe the harmonic is bad as I had it machined a few months ago to fix the seal surface and my machinists usually tells me if the parts bad.
I've heard that you're not supposed to tow heavy in 5th (overdrive) as the needle bearing for 5th can go out. Something about it having a plastic cage instead of metal? I dont' know how true that is though, but if it only makes noise in 5th gear, its probably an issue with 5th gear...
Gear rollover noise is a low speed issue AFAIK, so wouldn't show when going faster.
Mine has had a similar noise in 5th gear as far back as I could remember. It’s probly something opposite of good, but nothings happened yet. Everything is wore out, so I’m scared to investigate lol
I've tried isolating and it's definitely in the transmission. I was able to notice the noise in other gears when I did this. Although it much quieter in the other gears, 5 th is the only one that has it loud.
I've taken the transmission out but I've found a crack in the rear case. Should I start looking for a new transmission case or can it be welded? I'm not trying to break the bank on this.
Is this amount of slop normal? I know from pictures there usually is some but I can't tell if mine is excessive. I be this t case has been into before as the chains is a Morse brand and the rtv was not factory style.
Find the crack and win valuable prizes? I don't see it. But it's cast aluminum and special welding procedures should be followed if you go that route. Be aware that weld zone on aluminum reduces the strength of the welded metal. Get professional advice on welding up a crack.
Maybe it's only a surface crack? Not leaking fluid? Perhaps a liquid metal application will do? JB weld or other epoxy may be better that welding and creating a heat affected zone.
I found a guy who was willing to do the repair on such a small crack. He cut into it with the grinder then filled it back in with a tig. We cleaned it and pre heated to remove any moisture. The crack hadn't gone deep enough to reach oil yet, so I feel this repair was sufficient.
Find the crack and win valuable prizes? I don't see it. But it's cast aluminum and special welding procedures should be followed if you go that route. Be aware that weld zone on aluminum reduces the strength of the welded metal. Get professional advice on welding up a crack.
Maybe it's only a surface crack? Not leaking fluid? Perhaps a liquid metal application will do? JB weld or other epoxy may be better that welding and creating a heat affected zone.
It was a hairline fatigue crack on the web between the bolt hole for the tcase level and the gear casing. Still a surface crack but it was heading into the gear case. Unfortunately I'll have to live with the heat affected zone. Hopefully it doesn't reduce the surrounding strength much. The welder built up around the area to beef it up. The area didn't get crazy hot either, while uncomfortable to hold you hand close to the weld, it was not incredible hot.
This thread is diverting a little from the original issue with 5th into more general drive line issues.
I got the truck reassembled, with the t case rebuilt (new bearings and seals with pump arm fix). I had clutch issue come up which is why everything was removed.
I have what I believe is a drive line vibration above 62 ishmoh (speedo is ~10-15 off). I haven't changed anything about the rear driveshaft since taking it out with the transmission. About a year ago I rebuilt it with new slicer u-joints and a new carrier bearing. I don't remember there being such a vibration before removing the transmission. I did notice two things.
1) rear u-joint at pinion is stiff and has a spot in the rotation where it hangs up just a little.
2) The u-joint caps don't fill the space on the rear yoke perfectly. There are two tabs one on each side of the pinion that holds the u joint caps in as seen in the photo. When I installed the joint it has a little play better these to tabs. Is that normal? I would think it could cause centering issues.
I plan to replace the u joint, but I'm also concerned about this yoke issue. Anyone have some input?
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5th Gear noise
