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#3915242 - 03/29/18 12:45 AM Fluids for 78 Grand Marquis HELP
HuggySnacks Offline
n00b

Registered: 07/09/16
Posts: 46
Loc: Central Illinois
Hey guys, I got a couple problems. I think my GM might have a transmission leak and may need power steering fluid. last summer when I was driving the gears shifted fine. I stopped to get gas and after I filled up I could not get out of 1st gear. It would get up to second gear then just start slowing down right before it would usually shift to 2nd. The car wasn't running rough at all on the way home. Since then the car has been in storage, and I have been away on work. I am finally home and ready to get this beast on the road. I am certain that I put trans fluid in it before like 3-4 years ago, but I cant remember. It has the 400ci engine. Is the Trans in this car known to have issues like this?

I am getting a lot of grinding when I turn the steering wheel also. probably only after about 4 inches of turn. Also a lot of air, almost sound like im on bags from the 90s. I looked at the joints and everything seems to be okay with those. Any other ideas then power steering fluid?

Thanks for the help guys, I wish I had a garage but lifting a car up like this on a hill doesn't seem like fun lol.
_________________________
2011 Police Interceptor 85XXX miles (it purs)
1978 Mercury Grand Marquis 70XXX miles (I pur to it)

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#3918602 - 04/01/18 06:47 PM Re: Fluids for 78 Grand Marquis HELP [Re: HuggySnacks]
MBurns Offline
n00b

Registered: 05/13/15
Posts: 41
Loc: Massachusetts
A 78 Marquis is a really nice car, the quality on those is right up there with Lincolns of the time, they were truly built to last. Hope you get a chance to enjoy it this summer.

I'm not an expert on either of these topics but I own a 78 Town Car also with the 400 motor. Mechanically real close to yours.

Assuming the engine is still running OK,

I know on these C6 transmissions they use a vacuum modulator (just a diaphragm really) to tell the trans what kind load is on it, if that's blown out or vacuum leak to it you can get poor shifts, bad shift timing, things like that. There is a vacuum line that runs back to the trans, if you have a vacuum guage you can check for vacuum at the modulator with the car running (check at the end of the rubber hose, and check the modulator itself to see if it will hold vacuum. That's all I can offer, other than checking fluid level and condition. The C6 is a very stout transmission, they tend to give reliable service even in high power applications.

With the grinding and air sound you could check for power steering leaks so you know if you're drawing air in somewhere and getting an air pocket, bleeding the system of air may help (simple procedure ). Where does the sound seem to be coming from?
_________________________
Past
09 Grand Marquis
99 Town Car Touring
Current
06 Town Car Signature
78 Continental Town Car

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#3918722 - 04/01/18 09:52 PM Re: Fluids for 78 Grand Marquis HELP [Re: MBurns]
HuggySnacks Offline
n00b

Registered: 07/09/16
Posts: 46
Loc: Central Illinois
The grinding and air seems to be coming from between the steering wheel and the wheels which does tell me that I probably do need to bleed the PS fluid out most likely.

I am definitely low on transmission fluid. Not dangerously low, but enough to give it some. Do you know how those modulators usually blow out? It just seemed really odd that it was fine on the way to the gas station. I appreciate the help
_________________________
2011 Police Interceptor 85XXX miles (it purs)
1978 Mercury Grand Marquis 70XXX miles (I pur to it)

Top
#3918834 - 04/01/18 11:52 PM Re: Fluids for 78 Grand Marquis HELP [Re: HuggySnacks]
MBurns Offline
n00b

Registered: 05/13/15
Posts: 41
Loc: Massachusetts
A modulator going bad is usually a case of a hole in the rubber diaphragm which is just age and dry rot catching up. The modulators are very simple, just the rubber, a spring, and a rod that goes to the throttle valve.

With the PS pump if you still have a whining sound and grinding after a bleed I'd think about changing the pump. Could be steering box too but that's unlikely.

I think in the Marquis they used hydro boost system as with the Lincolns so the PS also provides boost for the power brakes, so you definetely don't want that going out on you somewhere.

You're welcome
_________________________
Past
09 Grand Marquis
99 Town Car Touring
Current
06 Town Car Signature
78 Continental Town Car

Top

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