T-5 Overdrive ratios

Kahuna

Kahuna

Well-known member
For you fellows that are T-5 knowledgeable, are there different Overdrive ratios available?
My friend & neighbor bought a 35 Ford pickup. Flathead power with a Saginaw or Muncie 4 speed and open drive line.
He wants an Overdrive & I suggested a T-5, but know little to nothing about them. I have read that there is a ratio of .62 or something like that
Thanks
Jim
 
As JSeery and I were just discussing in another thread, the V8 Camaro T5 that was factory available from '83-'87 has a 1st gear ratio of 2.95. This combination has an overdrive ratio of .63. As we alluded to in the other thread, you can replace the Camaro tail shaft housing with the housing from an S-10 pick-up to move the shifter quite a few inches farther forward, to a point not far behind the original Ford shifter location in the '35 pickup. The mechanical speedo gear can be easily moved to line-up with the hole in the S-10 housing, OR....you could also replace the Camaro main shaft with the S-10 shaft, which lines-up the speedo drive off the bat. The pic below shows the Camaro/S-10 combo, except that the V8 Camaro input shaft will have 26-splines. Simple swap!


The second picture (below) shows the location of the T5/S-10 shifter in a '35 Ford pick-up that we have done recently. DD


292542



368592
 
Hi Coop
Thanks for the info, but I was really wondering about different Overdrive ratios.
This truck he bought has an axle ratio of something around 3.5:1.
If the OD is .63, then in OD his ratio would be about 2.2. Not too good
Jim
 
Kahuna said:
Hi Coop
Thanks for the info, but I was really wondering about different Overdrive ratios.
This truck he bought has an axle ratio of something around 3.5:1.
If the OD is .63, then in OD his ratio would be about 2.2. Not too good
Jim
Click to expand...


Kahuna....I understand your points. A lot also depends on the rear tire diameter in use. Ironically, I have an old friend that ordered a new '83 Camaro with a 305 V8 and a T5. That car had a 3.42 rear gear in it, and it was very spunky...quite the pleasure to drive. I should note that the diameter of the tires on that year Camaro seemed rather short, which would help matters.


Unfortunately, O/D ratios are not necessarily easily changed on these transmissions, as the formula for figuring the O/D ratio also takes into account the tooth count on the input gear and the corresponding tooth count on the front cluster gear. And of course, the two O/D gear tooth counts figure into the formula. If memory serves me, it does seem like I remember one other combination of O/D gear tooth counts that will bolt onto the Camaro gear set that yields about a .74 ratio. One other factor that CAN complicate things is the spline count on the MAIN shaft. The bottom O/D gear in these transmissions must slide onto the specific spline count. Chevy transmissions usually have 27-splines. A Ford gear would not work because Ford T5s usually have 28-splines. Fortunately, the Chevy transmissions (all 27-splines) have several O/D ratios available. I'll see if I can find that ratio that I mentioned above. DD
 
Here is a link to a chart with all the ratios.Google is your friend


https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=7&cad=rja&uact=8&ved=2ahUKEwjS06X2n9HcAhWmyYUKHWx0DcEQFjAGegQICBAC&url=http%3A%2F%2Fwww.mongosgarage.com%2Ftech%2Ft5%2FT5Numbers.PDF&usg=AOvVaw13wv9H-cB0OIThoz7yyqCx


I used a GMC S15 WC( has Ford bolt pattern) in my 36 behind the 59A motor(Speedway adapter then Wilcap adapter to it).5th was .076 and I had a 9" rear with 3.73 R&P. Got the clutch disc from Speedway.I first tried 3.90's and that was to low.The only thing my 1st gear was super low which some folks call a stump puller.
 
Last edited:
FWIW I'm running a 1352-145 in my truck with a 3:54 rear end. First gear is a little low but it makes it easy to drive in traffic, just have to shift sooner. The OD is perfect for me, I use it all the time.
 
Kahuna said:
Hi Coop
Thanks for the info, but I was really wondering about different Overdrive ratios.
This truck he bought has an axle ratio of something around 3.5:1.
If the OD is .63, then in OD his ratio would be about 2.2. Not too good
Jim
Click to expand...

.86 is the highest available. With a 3.5 rear end, the OD ratio would be 3.01.
You could probably pull this OK with a mostly stock engine.
Most transmission shops can assemble a T5 from parts with the ratios you want/need. The really good shops can also add the trick mods to help keep it together for many moons.
Remember, even the best latest models were only rated at 335 ft.lb. torque.
You can button shift them but not with big hp ahead of them.
 
Beware that that the available OD ratios depend on which mainshaft you use. In other words, you can't have any/all available ratios, just a couple for each particular mainshaft.
 
Mike51Merc said:
Beware that that the available OD ratios depend on which mainshaft you use. In other words, you can't have any/all available ratios, just a couple for each particular mainshaft.
Click to expand...


Mike is correct about the main shafts, as the main shafts for the different intended applications (Ford, Chevy, Jeep, etc.) have a different number of splines at the rear end of said shafts...Fords has 28-splines, GMs have 27-splines, and Jeep has 23-splines. These splines are what the SMALL O/D gear rides on, so that NOT ALL SMALL O/D gears will necessarily fit on your particular main shaft.


Also beware that there is one more factor that comes into play when figuring O/D ratio. You must also consider the tooth counts on your particular INPUT shaft gear, along with the corresponding front gear on the CLUSTER gear that it meshes with. This can be shown via the formula for figuring O/D ratios below, this example being the 2.95 1st gear V8 Camaro gear set, with TOOTH COUNTS. DD


Cluster Gear = 31 Teeth
Input Shaft = 24 Teeth


Small O/D Gear = 25 Teeth
Large O/D Gear = 51 Teeth


Formula: 31 DIVIDED by 24 Times 25 DIVIDED by 51 = .63


In simple terms: 31/24 X 25/51 = .63
 
Another thing to consider when installing a T5 in an old car or truck, you will need a shift stick that is 14 or more inches long. This makes a very long throw between gears.
Luckily there are short throw adapters available. Most have a 2 inch riser block. If you want
an even shorter throw, you can go to a 2 1/2 or 3 inch riser.
 
You must log in or register to reply here.
Back
Top