Vehicle vibration when shifting to 3rd

Clutch, transmission, rear axle

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mkoecher
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Vehicle vibration when shifting to 3rd

Post by mkoecher »

In my '76 F250 I am having troubles when I shift into third gear. Usually when driving up an incline as I am releasing the clutch the whole vehicle will start to shake violently. No matter how I vary the clutch or throttle it will shake like crazy. If drop it into second I can continue driving at higher RPM's until the road starts to level out more or I can go up to 4th and just have the vehicle lug up the hill until it gets to a speed it likes in 4th gear. Also, if I'm already on the incline in 3rd gear there are no issues.

A friend suggested that it could be bad motor mounts. But part of me thinks it is the clutch or flywheel slipping, but I am wonder why it only happens in third gear and on inclines? Is it the torque demand I'm putting on the flywheel in that scenario? Anyways, anybody have this issue?

Thanks
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sargentrs
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Re: Vehicle vibration when shifting to 3rd

Post by sargentrs »

Check your motor mounts, tranny mount and crossmember bolts. The clutch on my F100 used to shudder badly. When I replaced the clutch it didn't look worn out. Had the flywheel resurfaced while I had it out. Problem went away. Don't know if it was the clutch or the flywheel but I'm leaning toward the flywheel since the old clutch still looked good and the flywheel had crazing and surface cracks.
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Manny
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Re: Vehicle vibration when shifting to 3rd

Post by Manny »

2nd on sarge there. You either have clapped mounts or clutch is glazed. Oil leaks coating the clutch can cause it as well. Check and see if oil is drippign from your bellhousing. That's the old bronco with the 3 speed is bad it's down to needing and clutch for sure.
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Busboy
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Re: Vehicle vibration when shifting to 3rd

Post by Busboy »

Clutches don't stop slipping when you go to fourth. This is something else.
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lamogo33
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Re: Vehicle vibration when shifting to 3rd

Post by lamogo33 »

I've had a similar experience before. It happened to be a bad third gear in the gear box. It was missing a portion of one of the teeth. Not sure if it would have hurt it to keep driving like that or not but replaced the gearbox for an affordable used unit.
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Manny
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Re: Vehicle vibration when shifting to 3rd

Post by Manny »

Busboy wrote:Clutches don't stop slipping when you go to fourth. This is something else.
Not slipping there going on chattering clutch due to hard spots and such. The trans could have a chipped tooth on third be he is stating on engagement which is whats got us thinking possibly hard spots on the clutch or oily disc causing chattering. Kinda tough to say without riding and driving in it..
Just another Ford fool named Dan.
The Junk that hangs around
67' F-250 highboy Camper special cross breed currently under way
http://www.fordification.com/forum/view ... 22&t=86706
1974 Bronco 302 3 speed
1984 bronco 302 c6 35's
1994 F350 7.3 5spd dually.
woods wrote: The rust holes in my truck were a factory install (very rare).
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Re: Vehicle vibration when shifting to 3rd

Post by Busboy »

If there were teeth missing on any gear in a manual trans it would knock like hell.
1967 F-100 4x4 custom cab.
Another 67 F-100 4x4 custom cab.
2016 F-150 Eco-Boost 2.7 liter. (It will smoke the tires!)
1972 F-350 Sport Custom cab & chassis.
1972 F-250 Explorer Special, Camper Special.
1971 F-100 custom. 302, C-4, p.s. p.b. factory 65 amp alternator with transistorized voltage regulator.
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colnago
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Re: Vehicle vibration when shifting to 3rd

Post by colnago »

Busboy wrote:If there were teeth missing on any gear in a manual trans it would knock like hell.
Is this because of a missing tooth/teeth, or because of material bouncing around inside the transmission?

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Manny
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Re: Vehicle vibration when shifting to 3rd

Post by Manny »

colnago wrote:
Busboy wrote:If there were teeth missing on any gear in a manual trans it would knock like hell.
Is this because of a missing tooth/teeth, or because of material bouncing around inside the transmission?

Joseph
The missing tooth gear set de meshing and re meshing
Just another Ford fool named Dan.
The Junk that hangs around
67' F-250 highboy Camper special cross breed currently under way
http://www.fordification.com/forum/view ... 22&t=86706
1974 Bronco 302 3 speed
1984 bronco 302 c6 35's
1994 F350 7.3 5spd dually.
woods wrote: The rust holes in my truck were a factory install (very rare).
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