Sponsored

What is wrong with my car? Bad U-Joint? Bad Differential/LSD?

Rodpwnz

Well-Known Member
Joined
Oct 14, 2019
Threads
5
Messages
190
Reaction score
160
Location
SF Bay Area
First Name
Rod
Vehicle(s)
2018 A10 PP1 401A GT
Hi Everyone,

Although I love my 2018 S550 Mustang GT very much, I've had my fair share of issues during these few years with it. Things from premature speakers crackling and seat cooler failing to multiple 10r80 transmission issues and eventual total trans replacement. Luckily, these have all been covered under warranty, and each eventually resolved after months of working with the dealer each time. My warranty just expired this past March right after the trans was replaced, and although 90% of my issues were resolved, a couple still remain.

1. I hear a clunk when engaging drive, reverse and sometimes at beginning of acceleration or deceleration.
2. When at low throttle and RPM, the power delivery seems to "chatter" or "wobble". It doesn't feel consistent, solid or smooth for power delivery. Maybe this is what others have referred to as the car "lugging"? At higher RPM(3K+), the car pulls smooth, strong and solid, its a night and day difference.

Either way, I believe these issues may have to do with my drivetrain, specifically U-joint or Differential. After doing tons of reading online and watching videos, I want to believe that I've narrowed the clunk sound down to a U-joint issue, but I can't be sure since I also think I hear a clicking or ticking sound coming from the diff/U-joint area when driving with windows down near a wall/divider that reflects the sounds from my car back to me.

I took the tech who replaced my trans for a ride along so that he could hear the "clunk" and he told me it's normal. Nothing about this seems normal to me, but I decided to continue listening to see if it continues or gets worse. I feel it's been getting more prominent lately, so I'm taking the car back to the dealer to get it checked out before it gets worse or causes damage to the rest of my drivetrain.

Just some notes: I have a 52,000 mile 2018 10r80 PP1 401A car with Magneride suspension, on 19x10 square wheels. I have bought but not installed a tune yet, I wanted to fix any mechanical issues first. I am hoping to have a track day first week of July so I have a lot I want to get done in the next month.

This community has been amazing, and I would consider the people to be one of the best parts of owning a mustang. Please let me know your thoughts and what you think I should do. Thanks!
Sponsored

 
Last edited:

SheepDog

Well-Known Member
Joined
Nov 3, 2018
Threads
18
Messages
2,247
Reaction score
2,597
Location
Colorado
Vehicle(s)
Iconic Silver 2022 MACH 1 HP
Broken Engine mount?

After a transmission replacement, I'd be looking at the trans mount, Loose bolts at the bell housing, flexplate, U-joint and CV on the driveshaft, as well as the carrier bracket for the 2 piece driveshaft
 

AZlb5.0

Banned
Banned
Banned
Joined
Nov 16, 2022
Threads
42
Messages
1,157
Reaction score
1,364
Location
Arizona
First Name
Carlos
Vehicle(s)
18 GT Premium
Agree with the above post. Look at your trans mounts and engine mounts. They might need replacement. My wife’s Yukon was getting that clunk sound when going into gear and it was her transmount.
 
OP
OP
Rodpwnz

Rodpwnz

Well-Known Member
Joined
Oct 14, 2019
Threads
5
Messages
190
Reaction score
160
Location
SF Bay Area
First Name
Rod
Vehicle(s)
2018 A10 PP1 401A GT
Broken Engine mount?

After a transmission replacement, I'd be looking at the trans mount, Loose bolts at the bell housing, flexplate, U-joint and CV on the driveshaft, as well as the carrier bracket for the 2 piece driveshaft
Agree with the above post. Look at your trans mounts and engine mounts. They might need replacement. My wife’s Yukon was getting that clunk sound when going into gear and it was her transmount.
Wow guys, thanks for the quick responses and suggestions! After looking into just motor mount and trans mount noises online, this could very well be the case. Excellent suggestions, thank you. I'll do some more research and also have the dealer check these out(including bell housing, flexplate, U joint, CV, carrier bracket).
 

SheepDog

Well-Known Member
Joined
Nov 3, 2018
Threads
18
Messages
2,247
Reaction score
2,597
Location
Colorado
Vehicle(s)
Iconic Silver 2022 MACH 1 HP
Wow guys, thanks for the quick responses and suggestions! After looking into just motor mount and trans mount noises online, this could very well be the case. Excellent suggestions, thank you. I'll do some more research and also have the dealer check these out(including bell housing, flexplate, U joint, CV, carrier bracket).
Make sure that they used locktite on basically everything they removed when doing the transmission replacement, just like the factory did. A lot of guys will just zap the bolts back into place with an impact gun and forget about it, but most if not all the bolts from the factory have thread locker on them
 

Sponsored

OP
OP
Rodpwnz

Rodpwnz

Well-Known Member
Joined
Oct 14, 2019
Threads
5
Messages
190
Reaction score
160
Location
SF Bay Area
First Name
Rod
Vehicle(s)
2018 A10 PP1 401A GT
Make sure that they used locktite on basically everything they removed when doing the transmission replacement, just like the factory did. A lot of guys will just zap the bolts back into place with an impact gun and forget about it, but most if not all the bolts from the factory have thread locker on them
The Tech who did the trans replacement seemed very knowledgeable, in fact, he is their #1 10r80 guy. I would have given him the benefit of the doubt on thread locker/locktite for install, but with all this happening, I'll ask them to confirm that as well. Especially so now that he had told me that the clunk sound is normal. They could just say "yeah we did it with thread locker" without actually have done it... LOL.

I also want to clarify again, that this "clunk" issue was happening while transmission was failing and for many months prior to trans total replacement. I and the dealer/tech had incorrectly attributed the clunk as a part of the trans failure, but now that it persists after they replaced with ford factory new trans, it must be something else.
 

SheepDog

Well-Known Member
Joined
Nov 3, 2018
Threads
18
Messages
2,247
Reaction score
2,597
Location
Colorado
Vehicle(s)
Iconic Silver 2022 MACH 1 HP
Well if it was happening before the transmission replacement it certainly could be a bad U-Joint or CV on the driveshaft, the carrier bearing, or maybe you broke one of the differential bushings or bolts. keep us posted and good luck.
 

HAVOC_5.0

Well-Known Member
Joined
Apr 26, 2023
Threads
3
Messages
507
Reaction score
771
Location
Maryland
First Name
Phil
Vehicle(s)
2019 GT
Just throwing this out there...

Unless the repair procedure calls for the technician to apply thread sealant or equivalent (Loctite), it was not done. If you have access to the OEM repair procedure, and can prove that it calls for sealant, then you can ask the dealer about that. If not, don't bother.

As far as your clunk is concerned, do you have access to a lift, or a friend that has one? If so, if you can easily duplicate the issue multiple times, get it on a lift and check with a tech friend. You will see the failed component with a visual inspection while duplicating the issue on the lift.

If you no longer hear it while in the air, that eliminates alot of components, and points you to suspension components that require load OR something in the driveshaft that requires it to be on the ground.

I deal with this all day. The only way to tell what it is is getting it to a qualified tech who is willing to spend some time chasing that noise.
 
OP
OP
Rodpwnz

Rodpwnz

Well-Known Member
Joined
Oct 14, 2019
Threads
5
Messages
190
Reaction score
160
Location
SF Bay Area
First Name
Rod
Vehicle(s)
2018 A10 PP1 401A GT
Well if it was happening before the transmission replacement it certainly could be a bad U-Joint or CV on the driveshaft, the carrier bearing, or maybe you broke one of the differential bushings or bolts. keep us posted and good luck.
Thank you, will do!

Just throwing this out there...

Unless the repair procedure calls for the technician to apply thread sealant or equivalent (Loctite), it was not done. If you have access to the OEM repair procedure, and can prove that it calls for sealant, then you can ask the dealer about that. If not, don't bother.

As far as your clunk is concerned, do you have access to a lift, or a friend that has one? If so, if you can easily duplicate the issue multiple times, get it on a lift and check with a tech friend. You will see the failed component with a visual inspection while duplicating the issue on the lift.

If you no longer hear it while in the air, that eliminates alot of components, and points you to suspension components that require load OR something in the driveshaft that requires it to be on the ground.

I deal with this all day. The only way to tell what it is is getting it to a qualified tech who is willing to spend some time chasing that noise.
I'll keep my eye out for this, and ask for the OEM repair procedure. I do not have access to a lift unfortunately but I'll ask around my car network to see if my friends do. I also have a great mechanic that is kinda far for me but I could ask to have him check it out. I might be able to rent a lift also, but I'll keep that as a last resort option. I could also ask the dealer to put it on a lift and try what you've suggested. Your test procedure is just to put it in D or R repeatedly while it is lifted to see if the "clunk" is reproduced?

I've called a motorsports mechanic closer to me and they want $200+ just to lift it and check/inspect. They claim it's an hour of work at the very least lol. From the other mechanics I've worked with, getting a car on a lift took less than 5 mins...and to check U joints, maybe another 5-10 mins? It is what it is!
 

HAVOC_5.0

Well-Known Member
Joined
Apr 26, 2023
Threads
3
Messages
507
Reaction score
771
Location
Maryland
First Name
Phil
Vehicle(s)
2019 GT
Yeah, their is a lot to it. I run a shop where I live and sometimes helping someone is easier than trying to get money upfront. Their are different sides to it because it is using resources that takes away from putting money in the register. But sometimes you secure a customer by doing it. Double edged sword for sure.

As far as your replication/duplication, that depends on what you do to hear the sound. If you have to drive it, being on a lift, you'll have to drive it. Not the safest, but we've done it (depends on the speed and circumstances). If you have to shift gears, load the trans, etc., it just depends. Basically whatever you're doing when you hear the sound is what you'll have to do on the lift while someone is underneath listening and looking.

I highly doubt the Ford Dealer will share the OE Procedure. I could look it up in Alldata and Mitchell for you tomorrow as it uses some of Fords Information but not the specific procedure, only what Ford is willing to share if that makes sense.
 

Sponsored
OP
OP
Rodpwnz

Rodpwnz

Well-Known Member
Joined
Oct 14, 2019
Threads
5
Messages
190
Reaction score
160
Location
SF Bay Area
First Name
Rod
Vehicle(s)
2018 A10 PP1 401A GT
Yesterday, I had a mechanically inclined mustang friend listen for the clunk while I went into Drive and Reverse while stopped and he heard multiple sounds coming from the back wheels/drivetrain. He heard a higher pitched "tick" or "click", as well as the "clunk" that I'm concerned about. These noises were inconsistent, so through my 5+ cycles of D and R, we both heard "clunk" and "tick" at varying times. He had the same "tick" sound in his S550 that he solved and believes it to be the Axle nut loosening. As for the "clunk", I still think it might be something else but maybe I'll try tightening the Axle nut anyways.

At this point I'm still incredibly confused, since I'm noticing the "clunk" happening inconsistently while slowing down in normal driving conditions, as well as when I'm slowing down in track mode at higher RPM while spirited driving. In track mode, I can feel it for sure since the trans/car does a slight "bump" with the clunk noise. I also think I can hear it once at the very beginning of acceleration from a stop, but harder to hear due to exhaust and engine noise.

My video link from late last year below, which at the time I believed the clunk to be part of failing trans, shows the same clunk noise that also happens when shifting into D and R. I'm driving in the video and the same clunk still occurs now, but not as noticeably. Maybe because I took the video on smooth roads and in a very quiet neighborhood late night.

The clunk sounds similar to the turn signal sound in our mustangs imo.

 
OP
OP
Rodpwnz

Rodpwnz

Well-Known Member
Joined
Oct 14, 2019
Threads
5
Messages
190
Reaction score
160
Location
SF Bay Area
First Name
Rod
Vehicle(s)
2018 A10 PP1 401A GT
Update - the random light "clunks" are unexpectedly rare now, but now I'm hearing a grindy and tinny sound when engaging Drive or Reverse. Mainly happens when I'm stopped and with foot on brakes. It doesn't really do it when I release brakes right as I switch gears. I should test to see if it happens when going from neutral to D or R...

I also am hearing a clicking/ticking noise from the rear axle area - I'm thinking it's either the axle nut or wheel bearing/assembly?

Luckily, I have video recording of both below:

Clicking/ticking when accelerating and decelerating:

Clunky/grindy noises when engaging D or R:

If anyone has any ideas, please let me know - Thanks in advance!
 
OP
OP
Rodpwnz

Rodpwnz

Well-Known Member
Joined
Oct 14, 2019
Threads
5
Messages
190
Reaction score
160
Location
SF Bay Area
First Name
Rod
Vehicle(s)
2018 A10 PP1 401A GT
Got almost the same noise. Did you figure it out?
Which one? The clicking sound when accel or decel? Or the creaky, clunky, grindy sound when engaging drive and reverse from a stop?

I've solved neither - but I suspect the clicky sound to be axle nut, or maybe wheel bearing assembly.

The Creaky, clunky, grindy D and P sound doesn't happen as often if I release the brakes when engaging. Still happens sometimes even when off the brakes, but not as consistently. I have no idea what it is, but probably driveline related. I'm thinking diff, u joint or driveshaft.
 

shadowx

Well-Known Member
Joined
Feb 8, 2020
Threads
18
Messages
167
Reaction score
41
Location
Missouri
Vehicle(s)
mustang gt premium 2019
I went to the dealer and they told me I have to change the driver axle shaft and the wheel bearing
Sponsored

 
 




Top