Pennock's Fiero Forum
  Technical Discussion & Questions
  Bad engine and/or tranny mounts can cause bad handling. Really? Explanation needed.

Post New Topic  Post A Reply
Email This Page to Someone! | Printable Version


next newest topic | next oldest topic
Bad engine and/or tranny mounts can cause bad handling. Really? Explanation needed. by Raydar
Started on: 09-10-2013 07:09 PM
Replies: 10 (876 views)
Last post by: Raydar on 09-11-2013 06:20 AM
Raydar
Member
Posts: 38529
From: Carrollton GA. Out in the... country.
Registered: Oct 1999


Feedback score:    (11)
Leave feedback





Total ratings: 451
Rate this member

Report this Post09-10-2013 07:09 PM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
I read this in another thread, and didn't want to hijack. Hence this post.
(I removed the name from the quoted text because I've been hearing this same statement from many different sources over the years.)

 
quote

Check your tranny mounts, if they're broken the car would sway when changing lanes


I've been hearing versions of this since I bought my 88 coupe in 97. I do not understand.

If the cradle is solidly mounted (or as solidly mounted as the pre-88 rubber bushings will allow) and the suspension components are in good condition (i.e., not moving around and changing the alignment) how can motor or tranny mount condition change the way the car steers.
The connections between the wheels and the transaxle are CV joints. They really don't care what angle the engine is sitting or twisting, as long as nothing is binding. (If the engine is moving around enough to bind up the CVs, I think you'll have much larger problems to worry about.)

Until proven otherwise, I don't agree.

Can someone please enlighten me?

------------------
Raydar
88 Formula IMSA Fastback. 4.9, NVG T550

Praise the Lowered!

IP: Logged
PFF
System Bot
tebailey
Member
Posts: 2605
From: Bay City MI
Registered: Jan 2013


Feedback score: N/A
Leave feedback

Rate this member

Report this Post09-10-2013 07:25 PM Click Here to See the Profile for tebaileyClick Here to Email tebaileySend a Private Message to tebaileyEdit/Delete MessageReply w/QuoteDirect Link to This Post
Put a few bowling balls in the trunk, then try a few high speed turns. Your shifting mass. That's what bad tranny and engine mounts will do. If your engine is swinging on bad mounts, your gonna feel it.
IP: Logged
John W. Tilford
Member
Posts: 289
From: Bloomington, Indiana, USA
Registered: Aug 2005


Feedback score: N/A
Leave feedback

Rate this member

Report this Post09-10-2013 07:33 PM Click Here to See the Profile for John W. TilfordClick Here to visit John W. Tilford's HomePageClick Here to Email John W. TilfordSend a Private Message to John W. TilfordEdit/Delete MessageReply w/QuoteDirect Link to This Post
That's one of the best responses I've ever read!
IP: Logged
John W. Tilford
Member
Posts: 289
From: Bloomington, Indiana, USA
Registered: Aug 2005


Feedback score: N/A
Leave feedback

Rate this member

Report this Post09-10-2013 07:35 PM Click Here to See the Profile for John W. TilfordClick Here to visit John W. Tilford's HomePageClick Here to Email John W. TilfordSend a Private Message to John W. TilfordEdit/Delete MessageReply w/QuoteDirect Link to This Post

John W. Tilford

289 posts
Member since Aug 2005
All except for the "your" instead of "you're", contraction for "you are". Sorry. Had a strict English instructor.
IP: Logged
johnt671
Member
Posts: 2263
From: sugarloaf pa usa
Registered: Feb 2001


Feedback score: (5)
Leave feedback

Rate this member

Report this Post09-10-2013 07:45 PM Click Here to See the Profile for johnt671Click Here to Email johnt671Send a Private Message to johnt671Edit/Delete MessageReply w/QuoteDirect Link to This Post
I can't go into all of the science that you are asking about, but a few years ago I had a scary experience with bad motor mounts. My 84 started to hit bumps or bridge seams and get loose. It felt like bump steer because the back would go up and wiggle around some, but it aways stayed straight when I held the steering wheel straight and settle back down. It slowly got worse until I drove across a bridge on a highway. The back of the car came up and started bouncing side to side so hard that the back of the car started to come around on me and I had to steer like I was on snow to stop the slide. As the shocks and struts had been on the car for a long time time I got a set of KYB shocks and struts, and took the car to a very trusted shop. I had them install the struts (I did the shocks) and check the suspension out. I didn't tell them what happened because I I thought the new parts would fix the problem. They did the work and called me up to say that if I got the motor mounts replaced I would have a nice handling car. They asked if I had problems with it so I told them what happened and they said they felt the same thing but not as bad as what happened to me. Since the car had close to 200,000 miles I had them do it. The car was so much better and was once again fun to drive.

Sorry to be so long winded but I wanted to explain it as best I could.
IP: Logged
tebailey
Member
Posts: 2605
From: Bay City MI
Registered: Jan 2013


Feedback score: N/A
Leave feedback

Rate this member

Report this Post09-10-2013 07:57 PM Click Here to See the Profile for tebaileyClick Here to Email tebaileySend a Private Message to tebaileyEdit/Delete MessageReply w/QuoteDirect Link to This Post
Oops, sorry missed the your in the proof reading.
IP: Logged
85 SE VIN 9
Member
Posts: 690
From: Harwood Heights, IL, USA
Registered: Apr 2010


Feedback score: N/A
Leave feedback

Rate this member

Report this Post09-10-2013 08:26 PM Click Here to See the Profile for 85 SE VIN 9Click Here to Email 85 SE VIN 9Send a Private Message to 85 SE VIN 9Edit/Delete MessageReply w/QuoteDirect Link to This Post
Very interesting. My 85 GT has a bad torque strut which I bought but haven't installed. The car wiggles uncomfortably turning at slow speeds and corners very poorly. It also bounces badly over railroad tracks etc. I already ordered Koni's, but I can see the PO had the mounts loose and installed new bolts. Wouldn't it be sad if I spent all that money when it already had new struts? On the other hand my 85 SE has known mount problems so bad I can see and feel the engine move, but handles much better than the GT. The SE has a poly aftermarket torque strut, but the bracket it attaches to the engine through is loose. I haven't been able to get the holes to line up to reinstall missing bolts. I just got the service manual from TFS. In trouble shooting these handling issues it mentions the shocks and struts many times (and also the sway bar, btw), but I don't think it mentions motor mounts. It certainly makes sense that a large mass like the motor could have a major impact on handling if it moved, but even if it did move (which it does to some extent anyway) it wouldn't be much, probably not enough to affect handling. If the engine moves enough to affect handling it's probably about to do something catastrophic imho.
IP: Logged
rourke_87_T-Top
Member
Posts: 1311
From: Toronto Ontario Canada
Registered: Jan 2009


Feedback score:    (9)
Leave feedback

Rate this member

Report this Post09-10-2013 08:41 PM Click Here to See the Profile for rourke_87_T-TopClick Here to Email rourke_87_T-TopSend a Private Message to rourke_87_T-TopEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by rourke_87_T-Top:

Check your tranny mounts, if they're broken the car would sway when changing lanes


The same way the suspension squats when under load or unloading, it effects the rear camber and suspension geometry. I'm no expert but I broke both my getrag mounts a couple years ago, sheared the brackets, the car was steering from the rear, all over the place on the highway.
IP: Logged
Raydar
Member
Posts: 38529
From: Carrollton GA. Out in the... country.
Registered: Oct 1999


Feedback score:    (11)
Leave feedback





Total ratings: 451
Rate this member

Report this Post09-10-2013 09:39 PM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by rourke_87_T-Top:
...I broke both my getrag mounts a couple years ago, sheared the brackets, the car was steering from the rear, all over the place on the highway.


Now, that I couild see. It sounds like, in that case, the the axles were actually holding up that end of the engine/tranny assembly.
I could see how that could put some abnormal deflection on the knuckles.
For "just" worn out rubber, maybe not so much, as long as the weight of the engine isn't "leaning" on the axles.

As for the engine just bouncing around, I could see it causing some bumps and thumps, but it seems like the mounts would have to be really fubar for the engine to get up enough momentum to throw off the balance of the car in any appreciable manner.

But it's all good info. Food for thought.
Thanks for taking the time, guys.
IP: Logged
rourke_87_T-Top
Member
Posts: 1311
From: Toronto Ontario Canada
Registered: Jan 2009


Feedback score:    (9)
Leave feedback

Rate this member

Report this Post09-10-2013 11:43 PM Click Here to See the Profile for rourke_87_T-TopClick Here to Email rourke_87_T-TopSend a Private Message to rourke_87_T-TopEdit/Delete MessageReply w/QuoteDirect Link to This Post
The only thing I overlooked when I rebuilt the entire suspension front and rear, poly trans, bushings, and/ or aluminum everywhere, Koni, Eibach, etc.

I shoulda known at the time but didn't want to wait for another order from RD, I noticed how thin gauge the original brackets were on the getrag, they became the weak links, the drivetrain was moving around on the tranny side probably only a few inches but it caused a very severe instabilty issue, at first I was unsure what was causing it but after taking a corner quite fast one night on the way to work, I spun the car around in an intersection, I know how to drive my own car as good as anyone, something wasn't right. The drivetrain was probably only moving a "few" inches on the trans side. It felt like the engine was trying to rotate 180*

I did replace them with the thicker ones from RD.
IP: Logged
Raydar
Member
Posts: 38529
From: Carrollton GA. Out in the... country.
Registered: Oct 1999


Feedback score:    (11)
Leave feedback





Total ratings: 451
Rate this member

Report this Post09-11-2013 06:20 AM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
Okay. Thanks for the info.
I have stock brackets on my Getrag, too, but the drivetrain is 5 point mounted to the cradle.
I try to keep an eye on those brackets. Give 'em a good look whenever I'm under there.

IP: Logged
PFF
System Bot

next newest topic | next oldest topic

All times are ET (US)

Post New Topic  Post A Reply
Hop to:

Contact Us | Back To Main Page

Advertizing on PFF | Fiero Parts Vendors
PFF Merchandise | Fiero Gallery | Ogre's Cave
Real-Time Chat | Fiero Related Auctions on eBay



Copyright (c) 1999, C. Pennock