i have a 51 with aflathead v8 and hd 3spd . i am putting a disc brake rear {free} but the ratio is like 277 with that ratio could i still use an s10 t5? or could i just use a car 4 speed and how bad would the shifter location be? on the hd 3pd what are the gear ratios non syncro? should i just use that? the truck will not stock thanks elliot

 

Hi Elliot,

This is all a matter of personal choice with regard to what kind of performance you are looking for from the truck!

If you want good freeway speeds and good gas economy at 65 then you need a rear end with higher gearing (lower numbers). 2.77 (if that's what you really have) will drive you at about 2650 rpm at 65 MPH with 15 inch wheels. But that's not a stock F1 rear end - maybe a 9". There is an rpm table on this site but I prefer this one.

Gear Ratio Calculator

Another thing to remember is that unless you have an overdrive transmission, all of your top gears will be direct drive ie. 1 to 1. 4spd, 3spd, 5spd, auto, manual - all the same. So what kind of transmission you put in really dictates the perfromance you want in the in between gears, for example: do you want to be fast off the line; are you going to be hauling loads; towing; lower engine horsepower, etc. Most overdrive transmissions have a 30% reduction (or .67 to 1) drive and htat's mainly for economy at freeway speed.

Here is a list of the gear ratios for some of the more common transmissions.

Tranny Info

I have a C6 and a Lincoln 9 3/8 inch rear end geared at 2.79. But I also have 412 HP FE 390PI driving that. So, climbing hills and getting up to speed is not a problem.

With your flathead, the S-10/T5 transmission would work ok, but it's not going to do a thing for you from a gearing perspective over your 3SPD. Both geared 1:1 on top gear.

If you are keeping your flathead, at it's mighty wapping 96 hp. about the only thing you might get from a performance standpoint is better freeway speed. And for that you'll have to have a rear end geared 3.00 or higher - maybe with an Automatic overdrive, or Borg Warner T-10 with overdrive for manual. Then you can install and use the stock column shift in your truck. (you can with any of the automatics too - you'll just have to make linkages - which is really easy).

I am using the stock column shift in my 51 withthe 390 and C6 - it's tight, but it works perfectly!

Good Luck,
Julie!

 

I ran my 85 hp flathead powered 38 Woodie with a 3.78 rear with a Columbia overdrive. The Columbia if I remember correctly is a 38 % overdrive so final gear ratio was in the 2.40 range. I only mention this since the Woodie weight is up in the F-1 weight range. It was a great highway cruiser with the Columbia but too steep a gear ratio for starting off in overdrive ( note that the columbia makes the stock 3 speed effectively a 6 speed). In my personal opinion the 2.77 rear will be a little steep for the flathead in your truck, particularly if you ever use it as a truck.
A comment on the 3 speed HD is to use it or hang onto it. First gear is non syncro and it is a spur cut first/reverse like the earlier flathead transmissions as opposed to helical cut like the later flathead transmissions including the light duty 3 peed that was stock in the F-1. I drove the HD 3 speed in my F-1 with a 56 Nailhead Buick V-8 in front of it. It was a good transmission. I replaced the stock light duty 3 speed with the HD 3 speed after several rebuilds to the stock trans. It did not like the Buick power and my, younger than, right foot. The HD 3 speed cured the problem.
I would think that a non overdrive trans with a 3.25 ratio rear would be just about right unless you are using it as a truck in which case probably a 3.50 would be a better compromise.

 

What rear are you using that is 2.77 and disc brakes? an 8.8 or 7.5? Either way, if a 9", I'd look into a third member swap to 3.25 or 3.50 as 49Willard mentioned. If an 8.8 or 7.5 I'd still consider a gear swap, but it would be more spendy and difficult. If no swap is in the works, I'd consider the T5 anyway, but you'll never use the OD or maybe even the 4th gear effectively. Overall inertia to get the truck rolling from a dead stop using a flathead, as Julie mentioned, is a strain on the T5. with those gears. I hate to say it, but sometimes free isn't all that free in the end. Knowing what the truck will be will help in your decision as well....cruising, towing, hauling, etc...

 

the rear is a disc brake rear out of a camaro, is told it was a 308 but the tag says 277. i was thinking of putting in the s10 t5 but i didnt think i would need the overdrive with this rear. i was thinking of using a saginaw 4 speed that i have with a speedway adapter. or is the hd 3speed worth leaving in does it have syncros in 2nd and third and what are the gear ratio this will not be used as a truck thanks elliot

 

By all means use a more modern trans, the original 3 speed has no synchros. BTW, what year is the camaro, and does it have an auto trans? friend of mine is looking for an auto for his V6.

 

the rear was 1982 up style ,all my friend had was the rear elliot

 

Not true; 5th in a S-10 T5 is .86, some are as low as .72.

 

havi,
I agree that there is no first/reverse syncro but as I remember (it was about 20 years ago that I drove Willard with that trans) 2nd/3rd on the HD 3 speed had a syncro. It was not a problem to shift. It is easy to verify by removing the 6 bolts and popping the top shifter off the case. The sycro just looks like a bigger light duty trans syncro. I would use the HD 3 speed unless it is bad since you do not need an adapter or a driveshaft mod. If there is a problem in the trans then I would think about a 4 speed newer trans with adapter and driveshaft work.

 

My bad, you are right. The HD 3 speed in 1951 should be with no synchro for 1st gear, and 2nd and 3rd do. They have helical gears, and 1st and reverse have spur cut gears. I had thought the HD 3speed (T-87) was all double clutching like the 4speed crashbox that I have.

 

The T5 is the Borg Warner transmission, I mistakingly looked at the Richmond 5 Sp which is 1:1.

I stand corrected. 5th is overdrive.

J!

 

thanks for all the replies i think ill leave the hd 3speed in for now,but will have to deal with the driveshaft because i will be shortening the frame to change it from a f3 to f1 thanks elliot

 

I'm also keeping the flattie in my 49 F3, but with a Dana 60 3.78. So what transmission would people suggest. It will be a daily drive. All that I would haul is a trailer with a yard of gravel a few times a summer, or 2*4's and plywood. I prefer to keep it manual, but I could go auto if that being the best choice. It will be mostly city driving, only the odd road trip. I was looking at a T-5 but am finding alot of negativity towards it in this sort of set up. I am collecting parts now, and have a year or so before I'd need the tranny, so it doesn't have to be the a tranny that I can find tomorrow.
Any suggestions would help.