'71 F100 Custom questions.

Clutch, transmission, rear axle

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James
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'71 F100 Custom questions.

Post by James »

Heh...I'll probably get called an idiot before I'm through here :lol: But, I'm just starting to learn about trucks, and I just got a '71 Ford F-100 Custom, It's suppose-to have a C6 transmission, and the guy said he put a '73 351 Windsor engine in it.

It runs, but I was wondering, what are some of the more common problems with these kind of trucks?
There's what I'm assuming to be transmission fluid leaking from it...Any suggestions of what to check first? (Seems to be coming from around the pan that's bolted to the underside of the transmission.)

(Heh, sorry I can't be more descriptive...I'm 18, but hey, gotta start somewhere, right?

I have a digital camera I could upload some pictures to show what I'm talking about if I can't describe something too well.)
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re: '71 F100 Custom questions.

Post by gonzalo medina »

Wipe down the most dirtyest areas where you guess it's coming from and then check on it every hour or so. The way your describing it it seems like a common gasket leak. Solution is to install a new gasket, which is a few bucks plus the new oil going in the tranny.
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re: '71 F100 Custom questions.

Post by jor »

As Gonzalo indicated, it's pretty hard to identify the origin of leaks with grease and muck on everything. I'd get some solvent or gunk or something and pressure wash it a few times. Then you'll be able to determine where the stuffs coming from. Is it engine oil, gear lube or transmission fluid?

If you don't have a pressure washer, now is the ideal time to bring this to your dad's or mom's attention. You might point out that this kind of neglect verges on abuse and could even be a reportable offense depending on how dirty that engine is.
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re: '71 F100 Custom questions.

Post by James »

Would the transmission being overfilled a bit cause it to leak some? (I didn't overfill it. Previous owner did.) Or would it not being cooled at all cause it to? I checked the dipstick after I let it sit and run for about 10-15 minutes
and it was over the maximum fill level.

Oh...one little question here, I thought I'd slip it in this post, how many fluids does it use? Like Transmission fluid, brake fluid, motor oil, anti-freeze, I want to know to make sure that it's nothing else that might be critically low.

The guy who had it before fixed it up just enough to run, so I'm surprised that most of the stuff on it seems to work fine.
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re: '71 F100 Custom questions.

Post by mytmatt »

Hello James, I don't think anyone here is going to call you an idiot for asking basic questions. No one was born knowing all about our trucks. There are lots of people here that know a great deal about these trucks, and I have never seen them be less than 100% willing to share their knowledge and expertise. It's pretty cool to be able to avoid the most common and basic errors because there is someone there to tell you what NOT to do. :D

Your truck should have:

Brake fluid: check at master cylinder, should be at or close to the top in both (front and back) reservoirs.

Motor oil: check at dipstick. Too much isn't good, too little is even worse.

Coolant: check at radiator cap, you ought to be able to see it. Your coolant should be around 50% antifreeze, and it's best to use a thermostat, though not everyone does. A thermostat restricts flow of coolant until your engine reaches a certain temperature, I like 180 degrees but opinions vary on this.

Transmission fluid: check at dipstick if automatic, with engine warm and running. If you have a manual transmission and you think it's low, it's more trouble, but you can usually put fluid in at the side, keep adding until it runs out the hole you're putting it in.

Gear oil in the rear end: this is something that rarely needs changing, and it's kind of technical to do so. Unless you have some reason to think you need to change it...a howl coming from the rear end, for example...I wouldn't worry about it.

That's all I can think of, if I left something out or just plain got something wrong, some of you more knowledeable people please point it out. :wink:

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re: '71 F100 Custom questions.

Post by James »

I'd like to start off with saying Thank you for all for your help and replying so quickly.

Yeah, changed the motor oil, and the radiator does have a thermostat thing, I think, The truck has to run for about 5 minutes or so before the Radiator gets hot, and when it gets hot, it gets hot in a hurry.
I just got a new radiator in it too, the old one was welded in a spot, and wouldn't cool the transmission, the new one has the little fin things much less dented and banged, and it has those spots to plug the transmission in...

But I kinda had to sneak the parts off my mustang's radiator, heh...(Hey, when I get a job when my truck runs, I can go buy new ones for them both, the old ones are a bit....Bent? They're like an adaptor on a tube thing.
But it had a little bit of transmission fluid in the lines, so I know it doesn't leak.)

(Note: The mustang doesn't run, so no worries, it'll be a while before it's fixed up enough to run, my brother is going to help me with that)
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re: '71 F100 Custom questions.

Post by James »

Oh. Just curious, what is the color of clean Transmission fluid?
And does the transmission have a filter like the engine does?
Hm....Also, how much of a pain is it to replace the rear main gasket thing?

(Edit: How hard should it shift? Should it do an audible "THUNK" and buck? Automatic transmission. Only does the 'Thunk' and bucking when going down the road, and sometimes it's soft and quiet, but definitely does shift 3 times without hesitation.)
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Re: re: '71 F100 Custom questions.

Post by mytmatt »

James wrote:Oh. Just curious, what is the color of clean Transmission fluid?

It should be a nice red. If it is dark red and leaning toward brown, and smeels burnt, then your tranny got hot and you should change it ASAP.

And does the transmission have a filter like the engine does?

Yes. It bolts to the valve body, which is accessible by removing the pan on the bottom of the tranny. It's a small sheet metal/wire mesh device, you should be able to tell what it is as soon as you see it.

Hm....Also, how much of a pain is it to replace the rear main gasket thing?

A BIG pain, assuming you mean the rear main seal. That is the seal at the back of the crankshaft. It can be changed with the engine in the truck by removing the transmission and partially disassembling the engine, that is the hard way to go about it. The best way IMO is remove the engine (you could say that is my preferred technique for fixing lots of things :lol: I like for things to be accessible) and replace the seal in your shop on an engine stand. Usually if the rear main seal is bad there are a few other things that are bad as well, and it might be an indicator that major engine work is needed.


(Edit: How hard should it shift? Should it do an audible "THUNK" and buck? Automatic transmission. Only does the 'Thunk' and bucking when going down the road, and sometimes it's soft and quiet, but definitely does shift 3 times without hesitation.)


Not that hard. It may need U-Joints and/or a carrier bearing, those are easy fixes. I'm not sure about the C-6, but other Ford trannies have a vacuum modulator that you can adjust your shift points with pretty easily.
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re: '71 F100 Custom questions.

Post by James »

Well, after hooking the transmission up to the radiator's transmission cooling part, another transmission cooler
and putting in some of that molasses they sell to put in there that's said to stop small leaks and help it shift
no problems on the shifting
though sometimes it does like to be difficult and not shift to third until I'm doing 50(I'm assuming topped out?)
This isn't an early sign of any problems, is it?
I can't ask my brothers, they drive something until it's just gone.

Oh...I was kind of curious about gas mileage too, it seems to be a bit low in that department, would eventually getting a 4-speed transmission help?
(Are there 4-speed automatic transmissions?)
I really don't want to take out the 351w motor in it that it has now for just some gas milage.

(Note: Going to be an every-day driving truck for a while.
Don't worry, I go the posted speeds and try my best to be careful :P )
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My '71 F100 truck on Car Domain.
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Post by spartman »

It might be.

If your tranny is shifting late it could be the bands need adjusting, the modulator is going out or the tranny is just getting old.

There are 4 speed auto's they are AFAIK all AOD's of some sort.

The ones I know of are the AOD,EAOD, and the ?4EOD?
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re: '71 F100 Custom questions.

Post by flyboy2610 »

If it's to the oint of needing molasses to shift, it's time to start saving for a rebuild. The clutch packs are getting worn.
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Re: re: '71 F100 Custom questions.

Post by ToughOldFord »

mytmatt wrote:Hello James, I don't think anyone here is going to call you an idiot for asking basic questions. No one was born knowing all about our trucks. There are lots of people here that know a great deal about these trucks, and I have never seen them be less than 100% willing to share their knowledge and expertise. It's pretty cool to be able to avoid the most common and basic errors because there is someone there to tell you what NOT to do. :D

Your truck should have:

Brake fluid: check at master cylinder, should be at or close to the top in both (front and back) reservoirs.

Motor oil: check at dipstick. Too much isn't good, too little is even worse.

Coolant: check at radiator cap, you ought to be able to see it. Your coolant should be around 50% antifreeze, and it's best to use a thermostat, though not everyone does. A thermostat restricts flow of coolant until your engine reaches a certain temperature, I like 180 degrees but opinions vary on this.

Transmission fluid: check at dipstick if automatic, with engine warm and running. If you have a manual transmission and you think it's low, it's more trouble, but you can usually put fluid in at the side, keep adding until it runs out the hole you're putting it in.

Gear oil in the rear end: this is something that rarely needs changing, and it's kind of technical to do so. Unless you have some reason to think you need to change it...a howl coming from the rear end, for example...I wouldn't worry about it.

That's all I can think of, if I left something out or just plain got something wrong, some of you more knowledeable people please point it out. :wink:

Matt
Great advise Matt, but you forgot the important one.....

gasoline!

:evil:
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re: '71 F100 Custom questions.

Post by mytmatt »

:lol: I was just happy to see some questions even I knew the answers to
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