Customs 1949 Mercury New Project Engine/Tranny/Rearend Question

I recently got this new project. I swore to myself I wouldn't buy another car I couldn't drive home the day I bought it, but here it is. Ultimately this will be chopped, but I am going to start from the ground up.

The pic was taken with a cell phone, quality sucks.

I have:
-a set of 670 15 white whites from Coker (Alliance purchase)
-spindles from Fatman w/cut coils (bought complete front end with these -drum to drum)
-all stock brake replacement parts

Since the picture I have taken all drive-train out from under car (almost forgot, no stock engine and tranny included in purchase) My question is, if I want to keep and use the stock rear end and I am going to run a Chevy 350 (I haven't bought one yet) would a Chevy TH-700R4 transmission keep the rpm's on the freeway (65 mph) low?

What are your thoughts on this combo? I know the basic suggestion will say get a 9 inch. I understand this, I am trying to do this on a serious low budget and if I can use something I already have I am all for that.

Any suggestions are greatly appreciated.

Thanks

username

 

Probably cheaper and better in the long run to use a 8" ford if you can find one the correct width.

 

Thanks for the suggestion.

I am really looking not to just go buy a new rear end. I am trying to work with what is here to achieve a decent running freeway driver and to keep costs down on the build.

If someone has done this combo with the 350 + 700r4 + '49 Mercury rear end specifically let me know. Or has anyone done a Chevy 350 + Turbo 350 + '49 rearend?

username

 

Be different, don't chop it.

Back in the day these Mercs were hot rods as well as mild customs and very few of them were chopped.

 

The trouble with the Merc rearend is the gear selection (or lack thereof); not the toughness. . If it was an overdrive model it probably had a 4.33. If it was a conventional 3-speed it might be a 3.78. A TH 350 isn't going to change anything since they run 1:1 in top gear. The 700R4 is an AOD I believe. If it is it'll handle the 4.33 but not as well as it would a 3.78.

 

If it was an automatic I recall mine being about 3.35.

What's the difference in cost from a 350 tb vs a 400R?
A modern rear end you can usually get for around $150.

In answer to your original question, I did run the 350/350 combo with the original rear end. It is strong enough. I never could get rid of a vibration problem with the original rear end. Didn't think it was worth it to completely rebuild the original rear end.

If you are going to just flip the car then yes, it is most economical way to go.

 

Isnt the Merc rear the same used in F1's?

 

I thought so at one time because they look so alike. Then my buddy said did you notice the spring pads on the F1's are on the top instead of underneath the axle?

 

This is not an automatic transmission model.

Not knowing much about gearing/ratios/rearends + transmissions can someone specifically explain what to do to determine which rearend I have?

 

What trans was in in it?

I'd leave it alone for now, and try to source a good deal on a used 8.8 if that's what fits perfect in the car (if the current gear ratio is high like a 4.30).

 

I asked the guy who took the engine and tranny, I believe he said 3 speed with overdrive.

 

Mark the rear U-joint.

Mark the rear tire.

Blackboard chalk works well.

Be safe, roll the car on a level surface.
Count driveshaft or companion flange rotations while turning the rear wheels one full revolution.
(Whichever you can see best.)

Four revolutions of the driveshaft and one revolution of the rear tire gives you a 4/1 diff ratio.

More than likely you won't come out with an exact figure so you'll have to pay attention to less or more than a full turn of the companion flange.
3.90/1 or 4.11/1 being somewhat typical ratios.

 

Fords of the era that ran overdrive transmissions had a 4.10/1 diff.

Standard sticks were - if I remember right - 3.89 and/or 3.78.

The Mercs would be similar.

You do have to watch out for the Spicer station wagon rear axles.
(ID'd by the sheet metal rear cover plate and 11" brakes.)
Fords with these and the OD trans had a 4.27 diff.

 

Ok great. Here are the results:

1 full tire rotation = 2.25 rotations of the drive shaft.

 

Not to hijack the thread, but since we're on the subject, what rearends are an easy swap into this car? I have a similar one and my rearend is missing. I have access to a lot of parts cars, I'd like to know a specific make and model of rearend that would be an easy swap.

If I get a 57-59 Ford 9", can I use those leaf springs too? Do they swap direct?

 

There is a lot of info on different 9" rear ends (years,widths,gears,etc etc), just do a search on the topic.

My issue is a little different and I am hoping this thread will not be redirected to another 9" Ford discussion.

Thanks

 

Yes I realized that. I had both rear ends side by side at one time. Other than gearing on certain models you should be able to cross ref. what people are running in trucks.
I bought my F1 off a guy who had a 283 Chevy and a 3spd with the stock F1 rear. It held up but it wasnt something you would run on the highway everyday.

 

It looks like you may have miscounted.
Far as I know there were no 2.25/1 passenger car diffs in that era.

You didn't happen to jack up one side, turn the wheel and count did you?
That works on a non-locking diff, but you need to multiply the companion flange rotation by 2.

 

C9-

You are right I spun just one side. The new results:

1 revolution on the tires = 4 rotations of the drive shaft

So with this rear end, will a 700R4 tranny keep the rpm's down with a Chevy 350 driving on the freeway (65mph)?

Thanks for all the info so far

username

 

Thanks for the info on the combo. Besides the vibration, how was it driving on the open road? High rpm's? What I am trying to do is determine if this will be a setup I can drive longer distances without the engine screaming.

"....flip the car..." Nope, this is the one I wanted & got.

 

I have a 9" out of a Granada, that's gotta be hard to find.

 

We put in a 68 GTO rear axle assembly (correct width) with ratio of 3.31 and used a 700R4 trans. 65mph is 1750rpm.
Ol Blue

 

My 49 Merc has a Ford 400 smallblock/C6 tranny/9", with 3.16 gears. At 65mph i'm doing 2500rpms. I still plan on putting 3.01's in it when I can. Should drop it to around 2000rpms.

 

The 3.35 was a bit high reving for me. Just personal preference. I'm with Bob on rear end preferences. My current rear end is more in the 2.9 range which I like (with 350 trans).

Sounds to me like your rear end is in the 4.0 range according to your test. I just checked my Merc manual and it says there were two axles ratios available, 3.92 standard and 4.27 optional. I do recall over the years on the HAMB, guys with of 4.00+ rear end ratios saying they almost had to stay on the streets. Their motors were screaming with 4.00+ rear ends ratios range. In your case, I don't know how to figure what the 700R will drop your revs down to.

Hopefully someone will chime in who really had a Merc with the stick shift rear end.

 

Several mph vs rpm formula's kicking around.

Here's mine:

TD x RPM divided by 336 x diff ratio = mph in high gear which is usually 1 to 1.

TD = Tire Diameter

RPM = you know.

336 is a constant

diff ratio, 3.00, 3.70, 4.11 etc.


Keep in mind that in real world use the converters stall speed can make a difference.

A high stall converter won't lock up and the slippage generates trans heat.

2400 works pretty good on the street although the next one of mine will be 2000-2200 rpm.

 

C9, does the 700R trans require adding another number to the formula? I believe a 350 tranny is 1 to 1 in high gear. The 700R must be a different number. What that is I haven't the faintest idea.

 

I think a 79 Lincoln will work

 

i used a rear from a 88-93 chevy s-10 blazer or pickup 4x4 only as these are the right width for it so that you can run skirts and hub caps. they have several different ratios and also some were posi traction. you have to move the spring seats though.

 

Instead of guessing, this time I looked it up in my Merc/Lincoln shop manual. First of all, as everybody knows, there were no automatics in '49-'50 Mercs. The book says that conventional 3 speeds had 3.91 gears; O.D models had 4.27 gears.

 

I bought my 49 Lincoln a few years back and I'm currently running a GM 350 CID out of a 1972 GMC TRUCK Holley 4B TH350 AutoTransmissio hooked up to my stock rear. It's been running like a champ...