Transmission Swap, T-5 in a F-1
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This web page is about restoring/resto-rodding a 1950 Ford F-1 pickup, and is
one of a series of articles documenting the project. I am providing this in the
hope that it is helpful to fellow Ford truck owners, but beware that there are
many ways to accomplish the same goals... I have only shown one way.
Also, keep in mind, that my comments are specific to this year, make and model,
and should not be generalized.
Feel free to drop me a line if you see mistakes or need more information, but
please understand if it takes me a while to respond. To go back to the
main project page click here.
After rebuilding the factory 3-speed transmission, I started to question if I really wanted to pursue that course. Keeping the original 3-speed had been my plan from the beginning, but in doing so I was going to have to swap out the rear axle for one that I could get "highway" gears for. That's not a issue - a Ford 9" out of a 1957-1972 F-100/F-150 fits. But highway gears kill acceleration. The factory 3.73 gears are a good fit for a truck... what I really needed was an overdrive transmission. So after spending the money rebuilding the factory 3-speed, I decided to transplant a Borg Warner T-5 transmission into the truck instead. This is a relatively common swap, and both the transmission and adapter parts are readily available.
Selecting a T-5The Borg Warner T-5 was one of the first mass-produced 5-speed overdrive manual transmissions used in the US. It was introduced in 1981 (in the AMC Spirit), but quickly made its way into many American cars, although a lot of people associate the T-5 with the Ford Mustang. That's probably because in 1985 the transmission was upgraded to what is known as the "World Class T-5" for use in Mustang GT's, and several other ruggedized variations of the T-5 followed (e.g. the "Z spec" transmissions for the Mustang Cobra). Over its lifespan, the T-5 was adapted to a bewildering number of different applications, and parts are readily available. When the T-5 finally ended its long use in OEM applications, Borg Warner sold the T-5 design to Tremec, where it is still in production.
Adapting a T-5 to a flathead is relatively easy, but you need a T-5 that has the shifter located as far forward as possible (most of them, like the Mustang T-5, have the shifter placed far back on the tailshaft housing). The T-5 used in the early Chevy S-10 pickup has the most forward shifter placement possible (without resorting to a remote shifter, which should be avoided), and can be made to work on a 48-52 Ford F-1. This is not the "World Class" T-5, and is generally referred to as the NWC T-5 today, but its plenty stout for a mild Flathead.
Here is our parts list. Keep in mind we are adapting a late model ('49-'53) Flathead to a T-5. If you are adapting a early flathead you will need a different adapter (also available from Wilcap).
- T-5 transmission, from a 1980's Chevy S-10 pickup with a V6, we ordered a rebuilt unit from Mac Van Pelt with a 3.76 first/0.72 overdrive and mechanical speedo, $950 plus ~$100 truck freight.
- Wilcap bellhousing adapter kit, P/N BH 59A-350, $265 (you can also order from Speedway, either the Speedway of Offenhauser brand). The kit includes an aluminum bellhousing adapter, throwout bearing sleeve, mounting hardware and pilot bushing
- A transmission mount, NAPA P/N 620-1255 worked for us
- Stock clutch release bearing (throwout bearing), NAPA P/N N1087
- Pressure plate. We used a Clutch Masters P/N 351519, $48. More on this below!
- A ~10" clutch disc, with a 14-spline x 1" diameter input, we bought it from Wilcap for an additional $85. You can use NAPA P/N RFC4203. There is nothing magic about clutch discs, it just has to have a 14-spline x 1" input, the hub must clear must clear the pilot bushing, and fit your pressure plate (disc must be smaller than your pressure plate bolting flanges, no other interferences).
- Your factory clutch release shaft, fork, equalizer rod, etc.
- The factory bellhousing, which the starter attaches to. Sometimes this is also referred to as the bellhousing adapter, so to be clear here - this is the factory cast steel bellhousing that was used on 49-up flatheads with the 3-speed, which is in addition to the bellhousing adapter kit (which adapts T-5 to the factory bellhousing).
The Wilcap bellhousing adapter kit makes mating the tranny to the flathead easy, but the transmission mount is another story, so that's where I'll start. Altogether, the T-5 is about 13" longer than the factory transmission, and the T-5 transmission mount is ~7" further back and ~6" lower than the factory mount, and to make things worse, the factory crossmember is in the way. But the factory crossmember can't be completely removed because the master cylinder and brake & clutch pedals attach to this cross member.
The first step is to get the engine setting at the correct angle. We installed the engine with the factory tranny attached into the frame and used an inclinometer to get the engine inclination. We made all measurements from the flats on the air cleaner, and the angle was near zero, in other words, the carburetor is level (we expected this, but since we changed the intake wanted to make sure). FYI you can do this with the body on the frame, but we had the body off already, since the frame is to be powder coated. (Note: the remote oil filter is laying across the engine in the pictures, it will be mounted to the firewall when the cab is installed.)
After that, we mounted the T-5 to the flathead using the Wilcap adapter, and lowered it in the frame. We tried to salvage at least part of the factory crossmember, but it is simply not possible (we hoped by cutting off the tab on the bottom of the transmission, we could save the bottom flange, but even that won't work).
Above: (1) The T-5 with the Wilcap adapter attached, (2) the engine and tranny in the frame, notice that the factory transmission mount is in the way and note the "tab" on the bottom of the T-5, (3) the tab is cut off in, since it serves no purpose for our application, (4) cutting through the factory crossmember, (5) engine and trans in frame after cutting through the factory crossmember, you can see that we cut out about ~13 inches from the middle of the the crossmember.
We fabricated a new crossmember for the transmission mount using 2"x1/8 square tubing which provides a 4-1/2 inch drop below the bottom of the frame rail, which is what is needed to maintain a level carburetor and when using the NAPA P/N 620-1255 transmission mount. This is a stout crossmember because it has to replace the rigidity lost by cutting through the factory crossmember. It should be noted that although this mount is bolted-in, it cannot be removed completely from the frame (the 5"x5" end plates prevent you from being able to get out of from between the frame rails), however, the mount can be unbolted and slid back about 4 feet (all the way to the crossmember in front of the rear axle). If you're not up to fabricating your own crossmember from scratch, you can buy a pre-bent tubular one from Speedway (and others), and pay someone to cut it to the correct width and weld on the end plates. You will probably need a different transmission mount if using this (NAPA lists 3 styles for an S-10, which you should be able to make work).
The factory crossmember (to which the brake & clutch pedals and master cylinder attach) needs to be reinforced, even though the newly fabricated transmission mount is now the structural member. We boxed-in the cut ends, and fabricated another section from the 2" square tubing. In the 2nd picture above, the transmission mount is setting in the frame, and the reinforcement for the factory crossmember is held in with C-clamps. In the picture below, everything is in place after being powder coated.
After fabbing the transmission mount, it was time to install the clutch and mate the engine to the transmission for the final time. This is a straightforward process, but we ran into problems bolting the tranny to the Wilcap adapter. There are four threaded bolt holes in the adapter to which the transmission bolts to, but they were either oversized 7/16"-14 or undersized 1/2"-13. Even the local bolt store couldn't figure it out with certainty, but thought that they were undersized 1/2"-13. We re-tapped the holes for 1/2"-13 threads which solved the issue. The picture below shows the throwout bearing installed (look closely and you can see the sleeve which the throwout bearing carrier was pressed onto).
The next issue we ran into was the clutch... we had initially bought a NAPA P/N CA30 pressure plate, which is a diaphragm style pressure plate as opposed to the factory Borg & Beck style. This required re-drilling the flywheel to accept the later style bolt pattern, and we had this done at the time the engine block was machined, and the engine was balanced with the CA30 pressure plate. Now for the problem: when trying to depress the clutch pedal, it seemed to hit a hard stop immediately. In the end, we could find no interferences or other problems but the pressure plate was nearly impossible to depress. We believe this pressure plate was defective, i.e. we don't think that the CA30 pressure plate that stiff by design. Due to time constraints (the CA30 pressure plate is a special order) we bought a "long style" pressure plate from NAPA, P/N CA7346, which is the NAPA catalog replacement for a 48-52 F-1 . However, this pressure plate is much larger than the original, and interferes (barely) with the Wilcap adapter - the lever arms on the outside of the pressure plate do not clear the Wilcap adapter. A little grinding on the adapter would probably have solved the interference issue, but we decided to call Wilcap and ask for advice. Wilcap recommended running a Borg & Beck style pressure plate (like came from the factory), which we ordered from Clutch Masters (P/N 351519). This pressure plate is even more compact than the original, and has 12 smaller springs instead of the original 9 large springs, which should make for a smoother clucth action. Of the pressure plates we had on hand, the one from Clutch Masters was clearly the best quality, was made in the USA, and resolved all our issues.
In the pictures below: (1) the NAPA CA30 diaphragm style pressure plate, (2) long style pressure plate (NAPA RCF4376) on left, which is too big for the adapter, the Clutch Masters pressure plate which we used, and the factory pressure plate on the right, (3) the long style installed, you can see how close the lever arms are to the factory bellhousing, which interfered with the Wilcap adapter, (4) the Clutch Masters pressure plate installed, notice how compact it is!
I was told that that the input shaft was too long on a T-5 and it was necessary to cut of about 1/4" from the front of the input shaft. Perhaps with some earlier flatheads this is needed, but our flathead was from a '51 Mercury, and we did not have this issue.. in fact there's more than 1/2" clearance from the tip of the input shaft to the bore in the crankshaft.
Now to the drive shaft. The T-5 is more than a foot longer than the factory 3-speed, and the output shaft is different (27-spline), so the driveshaft has to be shortened and a different slider yoke installed on the transmission end of the driveshaft. The first task is to locate a slider yoke for use with the T-5. You can source one from a junk yard late '80s S-10 or buy one from Coleman Racing. Once you have your slider yoke, install it into the transmission all the way, then pull it back 3/4 to 1" and measure from the U joint centers to get your new overall driveshaft lenght. As it happened, the local driveshaft shop (U-Joints of El Paso) had a driveshaft of the correct length in stock. After installing the new driveshaft we measured 7 degrees with respect to ground... as the engine is angled down at 2-3 degrees and the rear differential is angled up at 2-3 degrees, this leaves 4-5 degrees for the u-joints to take up, which is well within reason.
The transmission came with a shifter, but I bought a Hurst Shifter off of eBay from zrchris. He puts together a nice package for people swapping a T-5 into custom applications based on the S-10 transmission. The nearest Hurst part number is 3910029 which is discontinued. My reason for buying the shifter was to get positive stops, which a T-5 needs to prevent "overshifting". The shifter placement is about 7" further back than the factory 3-speed, but this isn't a problem since the transmission cover in the cab is huge. A friend had a Hurst shifter stick, which worked quite well, only needing a little bend to the right side.
And finally, the speedometer deserves some attention. Our transmission came with a plug in the speedo hole, so we bought a GM Speedometer Housing from The Gearbox and a 22 tooth grey driven gear (.810" diameter). You'll need to check your transmission to make sure you get the right driven gear, there are 2 sizes, .810" and .870". The good news is the factory speedo cable works with this transmission - it threads right onto the Speedometer Housing.
Hits & Misses
Adapting the Flathead to a T-5 transmission is not overly difficult, but it does take time and require access to a torch/plasma arc and welder. We had the body off of the frame, which made the job easy, but you could probaby do this with the body on. Fabbing the a new crossmember was time consuming but most of the time as spent making sure we got the proper engine inclination. The adapter kit from Wilcap was slick but we were disappointed that the threaded holes for attaching the transmission were so poorly tapped, and it would have been nice if a little more warning had been given on pressure plate selection.
- Be careful when choosing a pressure plate!
- Make sure the pressure plate clears the transmission adapter plate
- Make the sure pressure plate isn't too stiff, you don't have as much leverage in the factory fork-on-a-shaft as you do in later designs
- Once everything is bolted up, make sure you can operate the clutch and spin the engine without interference!
- December 2009 - removed body, fabricated new transmission mount, sent frame out for power coating, installed transmission
- April 2010 - first test drive
If you're restoring an F-1 and need more info, send me an email
|Last Updated: Sunday April 04, 2010
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