1965 Convertible Unusual Driving Condition - Pulls to right on Accel or Decel

[Richard M.]

My good friend and fellow member Chuck McSheehy's fully restored Top Flight '65 Fuelie has a very strange issue. We've been diagnosing it for some time now, scratching heads, loosing hair, and getting a bit frustrated.

Here's what's happening......

On acceleration OR deceleration, the car pulls noticeably to the right. For example, at about 35mph in second gear, a full throttle launch will cause the car to pull right like it's being steered that way. After a steering wheel correction to get it straight, then cruising at about 50-60 mph, let off the throttle abruptly and the car pulls to the right again. I drove it myself and can feel it. Very scary.

We fully inspected all steering and suspension pieces, which have been fully rebuilt over the last few years as part of his restoration, etc. All is fine. Ball joints, linkages, tie rod ends, idler, control arm bushings, wheel bearing, wheels etc, all of which have been replaced or restored as part of his full body off chassis restoration a few years ago.

We brought the car to a friend's alignment shop a few weeks ago. Full 4 wheel alignment. Corrected some rear camber & some toe with shim rearrangement, and front shim work C/C and toe. The alignment came out perfect. We spent a good 2 hours on the rack to get it corrected, using John Hinckley's alignment spec guide for radial tires as the car is so equipped for road cruising off the judging field. It has knockoffs and all are tight.

Last week Chuck did some checks, and noticed the right rear trailing arm front bushing had much play, much more than the left. We decided to tackle replacement of both L & R bushings over the last few days. Upon removal of the right side bushings, we see deteriorated rubber on the periphery of the bushings, but the internal rubber seems fine to us. Both are now replaced and going back in the car today.

We're obviously going to have to get the alignment redone again. We're hoping this right rear bushing play was the cause of the unusual launch pulling to the right. But after seeing that the bushings were not totally faulty, we have reservations.

If you have any other ideas or things to check while we have it all apart please jump in with your thoughts.

Thanks,
Rich & Chuck
p.s. we pulled the diff to replace a leaky pinion seal while we had it apart too.

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[Edward B.]

Re: 1965 Convertible Unusual Driving Condition - Pulls to right on Accel or Decel

Very basic thought which you have probably considered: Check tire pressures and swap wheels from side to side to see if directional problem changes.

[Richard M.]

Re: 1965 Convertible Unusual Driving Condition - Pulls to right on Accel or Decel

Hmm, not sure if Chuck did that. Pressures OK. Will keep swapout in mind. Thanks.

[Stephen L.]

Re: 1965 Convertible Unusual Driving Condition - Pulls to right on Accel or Decel

I thought I had a trailing arm problem with symptoms like yours. Replaced the bushings and still had the problem. Mine was pronounced on accel. Found a suggestion on this board. Do some figure "8's" in a parking lot to free up the posi clutches. Fixed my problem. Because the car sits for extended periods the clutches evidently "stick".Worth a try....

[Edward J.]

Re: 1965 Convertible Unusual Driving Condition - Pulls to right on Accel or Decel

Rich, Steve's idea is likely right on, But my advice is to add a bottle of additive to rear diff and try the figure eights.If one wheel is driving the car this could be your result on accel.

[Richard M.]

Re: 1965 Convertible Unusual Driving Condition - Pulls to right on Accel or Decel

Thanks for the ideas guys.......We though also about a stuck posi clutch. Chuck changed the diff fluid and added the posi additive a few weeks ago. Still no-go then. However, he didn't do the figure eights then. After we do this work, if the problem persists we'll check the diff action again and do the figure eight tests.

Regardless, the TA bushings appeared worn so that was really needed anyways. A few more pics of the bushings show that the rubber is oval'd on the right side parts where the outer cap/sleeve joins the rubber. The left is not as bad, and wasn't that loose when on the car.

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Rights
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Lefts
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We thought the rubber was vulcanized to the sleeves, but on all 4 bushings that doesn't seem to be the case. Does anyone know if they're supposed to be vulcanized when new? We couldn't/wouldn't take his new pieces apart to check.


Rich

[Robert B.]

Re: 1965 Convertible Unusual Driving Condition - Pulls to right on Accel or Decel

Does the car have power steering? It could be the PS unit needs centering. I have the same problem on my '67.

Bob

[Edward J.]

Re: 1965 Convertible Unusual Driving Condition - Pulls to right on Accel or Decel

Does the car have power steering? It could be the PS unit needs centering. I have the same problem on my '67.

Bob

I have seen the centering of the control valve not adjusted properly and What I have noticed is when starting the car up the steering wheel will move left or right without your hands on the wheel, depending on how far off you are on the centering adjustment it can be severe or slight,

[Richard M.]

Re: 1965 Convertible Unusual Driving Condition - Pulls to right on Accel or Decel

Does the car have power steering? It could be the PS unit needs centering. I have the same problem on my '67.

Bob

Nope, no PS on this one.

[Ken R.]

Re: 1965 Convertible Unusual Driving Condition - Pulls to right on Accel or Decel

On my 65 in about 1968 I bought 4 new tires from Wards. They installed them. When I would give the car the gas, it would go to right. Let up on gas and it came back left. I swapped the tires around and found one tire a 4 ply tire, the other 3 were 2 ply/4 ply rated or something of that. The 4 ply tire was "stiffer" than the others. end up putting it on the front and no more problems. May not be a consideration with today's tires, but drove me nuts back then.

[Richard M.]

Re: 1965 Convertible Unusual Driving Condition - Pulls to right on Accel or Decel

We got it all back together today and after a morning brake bleed we're going to test it. Thanks for the ideas.

More to come,

Rich

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[Bill M.]

Re: 1965 Convertible Unusual Driving Condition - Pulls to right on Accel or Decel

We thought the rubber was vulcanized to the sleeves, but on all 4 bushings that doesn't seem to be the case. Does anyone know if they're supposed to be vulcanized when new? We couldn't/wouldn't take his new pieces apart to check.


Rich

In general, the inner sleeve is just pressed (shot is the industry term) into the rubber. It is possible to bond (industry term) the inner sleeve to the rubber, but it is more expensive and it is only used if the bushing durability is unacceptable without the bonding.

[Duke W.]

Re: 1965 Convertible Unusual Driving Condition - Pulls to right on Accel or Decel

What is the manufacturer, model, and size of the tires?

Also, I would like to know the make/model of the alignment equipment, and what are the final settings?

The equipment must be capable of measuring individual rear wheel toe, not just total rear toe. Unequal side to side toe can cause pull even if total toe is within the correct range.

One thing to check is circumference. Check and adjust as necessary cold inflation pressure to whatever the owner normally sets during routine tire pressure checks. Then remove vehicle load from the tire, and measure the circumferance with a tape measure. If they are more than about one percent different the car may pull under acceleration, especially with a Positraction axle.

If tire circumference is different by more more than one percent, it's probably worth having the larger tire shaved down to as close as you can get to the smaller tire circumference.

A 27" nominal inflated OD tire has a circumference of 27 x pi = 84.8",

If the circumference difference is 1.1 inch, shave off 1.1/pi/2 = .175" of tread depth.

Some repro bias-ply tires are notorious for poor dimensional conformity, and the typical cheap, low quality less-than-H speed rated radials that most guys install can also exhibit the problem.

Whenever confronted with pull, the first thing to check, especially with Positraction axles is tires - pressure, circumference, and radial and lateral runout.

Tires, particularly radials, can also exhibit pull due to internal structural issues than can't be seen or measured. I think the term is "radial tire lead". The best way to check this is to install a known good wheel/tire that measures within one percent circumference of the opposite side tire, temporarily on each rear side. If the substitute doesn't exhibit the pull, the original tire is likey defective and must be replaced.

Duke

[Ralph P.]

Re: 1965 Convertible Unusual Driving Condition - Pulls to right on Accel or Decel

I had this problem on my original '66 years ago....... found badly mismatched tread depth on the rear tires. One new tire corrected the problem.

[Richard M.]

Re: 1965 Convertible Unusual Driving Condition - Pulls to right on Accel or Decel

Update, Problem is solved. It was.........TIRES. We're all a bit embarrassed to admit it, but we have to fess up. All of you who suggested checking tires nailed it.

After completing the work to repair the trailing arm bushings and the pinion leak and after brake bleeding today, we looked more carefully at the tires.

Several years ago Chuck bought a pair of 205-15's for the fronts, and a pair of 215-15's for the rears to give it a little 'rake' in the rear for nostalgia fun. After the car was judged in Kissimmee in January with it's original knock-offs and bias ply goldlines, the new street radials mounted on reproduction knock-offs were reinstalled.

A mixup happened. The 205's went on the right, and the 215's went on the left. We knew as soon as we saw it, and after some sit down time with choice expletives and such, and after we swapped them out, car rides perfectly. Pull condition is gone. Makes perfect sense that the car pulled right with smaller width and diameter/circumference tires on the right. The Posi unit had to fight to stay locked, and the right side tires lost.

We all totally missed it. I did, Chuck did, and my friend who owns the alignment shop did, probably assuming we checked the tires. We really goofed, but learned a valuable lesson. "Look at the simple stuff first." Chuck is very happy that his car is fixed, me too.

Thank you to everyone and all of your ideas to help us solve this problem.

Rich & Chuck