I interested in what gear ratios others are running with your FLATHEAD V8 and a STOCK 3 speed transmission.
I'm swapping out the Dana 41 for a 9" with lots of gear choices.

The LD 3 spd has a 28t cluster which gives me 1st = 2.82, 2nd = 1.60. With 22575r15 tires @ 28.4" tall I can't go to high a ratio.

By the numbers with a 3.50 I will turn about 2400 @ 60.

What gear ratio are you running? How do you like it?

 

I agree with approximately a 3.50. But before you go through with the 9 inch swap, you need to be informed that a new company is now offering R & P swaps made specifically for the Dana 41. https://www.ford-trucks.com/forums/1...nd-pinion.html

 

Well having gave away two 5 speeds , and now iam going to be running the t98 4 gear , and the flatty will be running a merc 8cm cam , electronic ignition , eab heads , a merc 4 bolt intake and a rochester 2 jet i settled for the 8.8 diff out of a parted 87 or 88 merc / vic with a 3.08 rear gear . poor mans overdrive and i should be able to pull more than 45 on longer trips on the open road as compared to theoe 3.92 gear it had oe .......

 

I went the 9" route, with a 3.50 ratio. I also traded for a 3.25 center section and tried both. With the 3.25, I had to use a lot of clutch to get away from a stop, and going around corners in 2nd in town I'd have to slip the clutch. With the 3.50 I have no excessive clutch work, and cruise at 60 - 65 and 2300 RPM. Flatheads are only 239 cu. in., you need to spin them a little to have reserve power for hills and such, especially in hilly/mountainous country where I live, also with an altitude penalty. Not like running all day at higher RPM will kill them, either, they have very light valve trains and large bearings. With modern oil they last a long time.

 

Good info thanks Ross. The Dana gears are pricey. Not bad if you don't have another option. The 3.50's with the vac advanced should give good mileage.

Ross,
Did you need to shorten your driveline or will the longer yoke make up the difference?

 

You need a longer driveshaft with a 9". What do you mean by "longer yoke"?

 

[QUOTE=1950FordF1;16299968]The Dana gears are pricey. Not bad if you don't have another option. QUOTE]


Sure they're pricey. It's the first time they've ever been offered. But if you put it up against the time and money needed to find and purchase a 9", umpteen hours to fabricate the spring and shock mounts, paint, new driveshaft, U-joints, backing plates, etc., I'd call it a bargain.

 

Got it Ross. The longer yoke is 5" long. I haven't dissassembled my 3rd member yet but it looks like the shorter 4" pictured.

Doc, the pre 72' F100 9" is a direct bolt in. The F100 9" run $1-200 out here.

 

I'm using a 9" with that longer yoke, it's barely acceptable. But I balk at paying $200 for a new driveshaft that's 1/2" longer.

The 9" isn't a true drop-in. The perches are spaced right, but not always at the correct angle. I paid $75 for my 9", and it needed $300 in parts and labor to replace broken/worn parts, plus the brakes were shot, another $150 there. New lower shock brackets are needed, new shocks, lots of little stuff. If you can get the D44 R&P installed and set up for $600 - $700, it's probably a wash compared to a 9".

 

When I tore my 56 appart, for some reason I found a Dana 41 under it, I guess some previous owner swapped it in for som strange reason.

But anyway when I decided to replace it with a 9" I took the measurement from the axle driveshaft centreline to the yoke centreline and that dimension matched up perfectly with same dimension on a 9" with a 5" long yoke.

 

Interesting to hear that the F100 spring pads may be different. My donor was a 1963 F-100 which has the same wheelbase as the F1. I would expect these to be the same but I will measure the housing angle when I mock it up to ensure the correct angle.
The 63 axle has the shock mounts welded to the housing, Online drawings show the 63 frame and the F-1 frame @ 34", will keep in mind to check this when i mock it up.

Thanks for the input.

 

I was basing my advice on Albuq's experience with a "direct bolt-in" swap. That stuff adds up quickly.

 

Fresh off the phone w/ Early Ford Sales in S.C. The 3:54 gear sets for the Dana 44 rears in our old trucks '48-'52 are NOT ready yet . The spokesperson for EFS said call back on a monthly basis and I definitely will . Will purchase the gear set when available . Yukon gear has them but at near $250.00 more . EFS is closer than Wash. state to save on shipping . Also their price is near $860.00 .

 

But they do have the sets for the Dana 41? Right? That was the really surprising part of that thread I posted above. Although there was an option for replacing the Dana 44 sets, nobody had ever made them for the Dana 41 in our trucks.

 

Previous time when speaking to EFS he said the choice to have a 3:54 gear set made for the Dana 41 rear end was an error in judgement . He said the Dana 44 should have been first since more demands were for that rear . A 3:54 gear set is available for the Dana 41 rear .Will just have to be patient & wait till it is available .I will have the 3:54 gears in the stock truck as soon as they are available .