Ford Automatic Q

[C9]

My long-time pal traded his 29 full fendered roadster a few months back.

Now he's got a 46 Ford two door sedan with SBF 302, automatic and 8" rear axle.
Nice car on the outside, paint & upholstery etc., underneath some work shoddily done, but he's getting that ironed out pretty good.

Anyway the trans had a problem so he pulled it and had it rebuilt by a local trans shop touted by many to be the best in the city.
A non-OD trans fwiw.
(C4?  It's physically small.)

When he got the trans back in, it wouldn't shift into high.
Took it back, trans guy found a leaking vacuum modulater and replaced it.

It still won't shift into high.

I'm thinking there's an external vacuum line problem, but we didn't have a vacuum gauge with us and the car's too low too crawl under.

He's thinking vacuum leak, I'm thinking line disconnected somewhere and for all I know the line could be plugged into ported vacuum.
And, ported vacuum shouldn't be a problem since it follows manifold vacuum fairly close once you come up in rpm a bit.
The previous owner's a nice guy, but a bit lacking in automotive knowledge.
He trades cars, drives em for a few months and trades again.


I had the vacuum modulater vacuum line fall off my T-400 once and all that happened there was that shifting occured earlier rpm-wise than it had been.


Another question I have pertains to the 8" rear axle.
I believe these came in passenger cars, Granada, Maverick, etc.

What's the lowest ratio they could come in?

It's conceivable that if . . . the diff ratio was low enough he could be getting fooled because the car is so quiet.
I haven't driven it or ridden in it yet.
He's clocking 3000 rpm at 50 mph.
The rear tires are 26" and running the formula with a 4.11 ratio indicates he should be doing about 57 mph with that combo of tires and diff.

It's not a large speedo error like you'd think since three of us went on a 120 mph poker run yesterday and were the only hot rods in the midst of maybe 200 Harleys.
We were passed by everyone since the 46 was floating between 50 and 60 mph which was verified by the speedos in my roadster and the other car.
Fwiw, my speedo is pretty accurate.
I went to a lot of trouble to get the right carrier/adapter/whatever you call it and gears right.

The Harley gang was cool, but kinda funny.
When I asked how come so many Harleys were on a hot rod run they just laughed..... :?

[tom36]

Jay, can't help you on the tranny problem, but 99% of the 8" rears I have found are in the 2.70ish range.  I found one (and only one) with a 3.00 gear.  Aftermarket gear sets in lower ratios are available, but as I said, the lowest I have ever seen in a factory setup is 3.00.  Tom...

[Deuce]

The vast majority of 8 inch center sections are 2.79  :cry:

Ford made these ratios

2.33
2.79
2.80
3.00
3.25
3.40
3.50
3.55
3.80

The 3.50 and the 3.80 especially ... are rare.
Aftermarket ratios are available ...

.

[enjenjo]

Factory ratios were 2.79, the most common, 3.00, 3.23, 3.55, 3.80, and 4.09. The 4.09 was an optional ratio on early Mustangs. I have personally owned at least one of each, except the 4.09.

On a C4, if the kick down linkage is not adjusted properly, it can keep it from shifting into drive.

[C9]

Factory ratios were 2.79, the most common, 3.00, 3.23, 3.55, 3.80, and 4.09. The 4.09 was an optional ratio on early Mustangs. I have personally owned at least one of each, except the 4.09.

On a C4, if the kick down linkage is not adjusted properly, it can keep it from shifting into drive.

That sounds like what could be happening.

Gonna head up the hill with vac gauge and see what I can see.

Thanks guys.

[58 Yeoman]

I put a rebuilt C4 in a Mustang years ago, and it wouldn't shift right.  Took the mod out and found the rebuilder never installed the rod.  Put the one from the old trans in, and everything was fine.

[Crosley.In.AZ]

C9.....

IF the trans is a C4:

does the trans back up?  Is reverse good and solid? Burn out in R ?

This will indicate that the direct clutch is good.

No 3rd gear shift can be a few items:

Stuck v-body valves,

poor or no vacuum.

modulator pin gone , modulator valve stuck

Is this a thread in or push in modulator?

[C9]

C9.....

IF the trans is a C4:

Looks like your pic and the trans guy called it a C4.


does the trans back up?  Is reverse good and solid? Burn out in R ?
This will indicate that the direct clutch is good.

Don't know about the burnout, but it backs up ok.


No 3rd gear shift can be a few items:

Stuck v-body valves,

poor or no vacuum.
Vacuum isn't so great.
10" at idle with what sounds like a stock cam.
15" when the engine is spun up to 1500-2000 rpm.
The vacuum line to the trans is manifold vacuum.
The modulater line was found off the modulater when we got the car up on the rack, but vacuum levels remain the same after we got the line hooked up.

I think the timing is retarded and the owner thinks timing is advanced.
We didn't shoot it with a light cuz his company showed up.

We did take it for a short drive, but it won't upshift to 3rd even when going down a hill and slowly easing off the throttle.
This, whether manually shifting from 2nd to 3rd or leaving it in drive.

It looks like the engine could have a vacuum leak, but he'll look at it later on tomorrow.



modulator pin gone , modulator valve stuck
Is this a thread in or push in modulator?

Don't know.
He's going to take the car back to the trans shop in the morning.

 The engine seems to run pretty good, but it's not as strong as I think it should be and that's considering the car is a 46 Ford 2 door and probably weighs 3400-3600# and the engine is an early carbureted 302.

He was told the engine had a hot cam, but I doubt it.
Everybody and their lying through their teeth brothers have an R/V cam in their engine, but don't have a clue as to the cams timing figures.

What it does have is equipment purchased for the 'wow' factor.
Chrome stuff which is cool, but it's got a double pumper up top and a Mallory distributor without vacuum advance . . . this last a pet peeve of mine.

If the trans shop proclaims the trans 'cured' and it is, we'll pop one of my spare carbs* on it and time the engine with a light.

*Smog Holley, like new, 600 cfm and/or a Carter 750 cfm jetted for 350' altitude (we're now at 3300') and jet er down if necessary.
I bought two of everything a couple summers back figuring I was going to rejet the Edelbrock in his 29 roadster, but we never got around to it although I did rejet mine.

I know, the 750 Carter is a big carb for a little engine, but it'll work ok as a test device.
The Carter/Edelbrocks are pretty much self-regulating vis a vis airflow so I don't see any problems there . . . except getting it back later....

[Crosley.In.AZ]

check for vacuum flow , best with a gauge to verify the vacuum is there.

Gauge should move with throttle stab -- you know the routine.