Driveshaft slack?

[Motorhead350]

Weird concern. Tonight I changed both u-joints properly. After install I noticed the popping went away as well as vibration while driving. The car still feels like it has a bit of a jerk and makes a noise when I brake hard and release before the car stops... like every time I release the brake pressure.

There is nothing wrong with stopping, but releasing the brakes under pressure does not feel quite right.

Normal or should I check something out?

Thank you in advance.

[fastblackmerc]

Weird concern. Tonight I changed both u-joints properly. After install I noticed the popping went away as well as vibration while driving. The car still feels like it has a bit of a jerk and makes a noise when I brake hard and release before the car stops... like every time I release the brake pressure.

There is nothing wrong with stopping, but releasing the brakes under pressure does not feel quite right.

Normal or should I check something out?

Thank you in advance.

Probably the normal drivetrain slack.

[tbone]

Maybe the diff needs some attention. Mine had a little clunk that I attributed to normal driveline slack, but after having it disassembled and shimming it properly, it's gone.

[Motorhead350]

Great thank you.

Frankly, if it's not going to break I am not concerned.

Time to turn up the Doo-Wop. :)

[tbone]

My pinion seal was leaking so it had to be partially disassembled anyway, or else I would live with it too.

[RF Overlord]

The car still feels like it has a bit of a jerk and makes a noise when I brake hard and release before the car stops... like every time I release the brake pressure.Might be just paranoia on my part, but I would check the brakes, specifically make sure the slide pins are properly greased and that the calipers move freely. Also check pad wear for anything that looks uneven.

Mary's car had a sticky piston on the front driver's side. Didn't make any funny noises until that half of the pad wore down to the plate and it started grinding. The other part of the pad still had plenty of life in it, but the rotor was ruined.

[Motorhead350]

I changed all pads this past month and the discs were just fine.

Good tip though.

[Wags]

Dom,

After driving the car a while (like out on the expressway) when you make a sharp turn from a stop (going slow, I know that's hard for you) do you hear any low groaning sound from the rear (gotta turn down the music for a bit for this :))? The binding only noticeable after a quick stop and then when you release the brakes some? If so it could be the clutch packs not releasing. This can be caused by not enough friction modifier or not enough gear oil overall. If that's the case you can pull the rear diff cover, check for metal filings, check for play in ring and pinion and check for any seals leaking. If ok, then button it back up, put new full syn oil and add new friction modifier. I use the oil with the friction modifier already in AND add the Ford friction modifier. Don't get the modifier from Autozone, get the stuff from Ford (it really stinks so don't spill it). After it's all back together, go to a lot somewhere and do SLOW sharp figure eights for about 5 mins or so to get the new modifier/oil worked into the clutches. This should do the trick if it is indeed your clutches (as long as they are not toast).

Wags

[Motorhead350]

Wags, the car is fine upon turns. I remember it got so bad once the car would make noise when I would switch lanes in bumper to bumper traffic! It only does this when I release the brake. Not taking off or turning. I am sure it's fine, but at the very least I will check the fluid level.

Thanks man!

[vegasmarauder]

That bump feeling from the rear end when releasing the brakes after a full stop is a good indicator of loose rear trailing arm bushings. The stopping inertia winds up the rear end housing and the brakes hold it in a "loaded" position. As soon as you ease off the brakes to go forward, it unwraps the rear end and you feel the slight bump.

When it gets really bad you can hold the brakes on hard, shift back and forth into reverse and then drive without moving the car, and you can see the entire rear axle rotating slightly back and forth (the pinion end will move up and down).

Depending on how and the surfaces the car has been driven on, they can fail by 80K-100K miles. It does feel like U-joint slop and is frequently mistaken for it.

[nusbd]

with the car in neutral, e brake on, on jack stands rock the driveshaft to check gear backlash, if its more than a few degrees i would look at working on the rear. I would suggest if you drag race the car to replace the crush sleeve with a spacer and shims.

[Motorhead350]

Thanks for everything guys.