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1954/64: F100/700 239/256/272/292.
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1948/52 F1/F3's used the Borg Warner T-9 4 Speed Manual Transmission.
I know this is a really old topic but I've been offered two t98s but owner says they have 1 3/8 input shafts. My 52 Mercury M3 has an 8ba and the non synchronized 4 speed.
I can find no reference to t98s with a larger shaft and he says they are from larger trucks with the 6 cylinder in them.
I've not pulled mine yet as I'm using the truck and he's 20 hours away. Assuming mine is 1 1/8 input can I have the shaft ground down, resplined? Will a T5 match my bellhousing? What is the input shaft size on a T5?
Speedway says the T98 is 1 1/16 but I think they are mistaken or they may be referring to the T5 input.
Any insite is appreciated as I'd really like to get rid of the crash box.
Oh, and yes I'm aware of the rear end issues so we don't need to go done that path.
The larger shaft on the t98 is no problem ,get the 11'' clutch disc and pressure plate and your good to go ,pilot bearing diameter is the same. If your flywheel is not drilled for the 11'' there are shops that can do that too. Alan
If you plan to retain the flathead, then the T98 from a flathead truck is only what you can use. The bellhousing-to-T98 bolt pattern is cast into the T98 case, which is different than all T98 cases after (gonna say) 1952. Visually compare the two side by side, and you can see it.
As for the T5, there are conversion kits to use one behind the flathead, and ultimately easier to install than an original T98 in anything other than an F4-F6, due to frame heights and crossmembers.
I added a couple pics to show a flathead T98 Notice the bolts are only accessible through the inside of the bellhousing.
If you plan to retain the flathead, then the T98 from a flathead truck is only what you can use. The bellhousing-to-T98 bolt pattern is cast into the T98 case, which is different than all T98 cases after (gonna say) 1952. Visually compare the two side by side, and you can see it.
As for the T5, there are conversion kits to use one behind the flathead, and ultimately easier to install than an original T98 in anything other than an F4-F6, due to frame heights and crossmembers.
I added a couple pics to show a flathead T98 Notice the bolts are only accessible through the inside of the bellhousing.
You can see my crash box has the bellhousing cast with the trans case. So I would need trans and that bellhousing half?
Your crash box is a Warner T9 or T8 transmission. The pre world war two transmissions were one piece castings like yours, post war in the USA got the half bell bolted to the crash box case. The T98 is the same casting half bell as the crash box half bell, but the hole where the transmission input bearing retainer centers is larger diameter in the T98 half bell. A good machine shop could bore out a crash box half bell for you if you found a T98 that was missing the half bell (hogs head).
the bell half mounted directly to the T98 is needed. The hogshead is used from what engine it was mated to. In my case, it's the hogshead from a 254CID. A V8 hogshead may very well need machining like 38coupe said. Personally, I have not tried fitting a V8 hogshead to it yet.
I put a T-98 right behind my 239 flathead. bolted right up. had to shorten the driveshaft, bt thats it.
Reamer
Talk about finding an old thread.
Interesting, haven’t switched to a T5 yet and I have one of these behind a 254 out of an F6 sitting on my garage floor. My three speed is noisy. If I take the brake off does it have a normal spline like for driveshaft like an F1?
Last edited by Christopher2; Apr 25, 2026 at 01:31 PM.
Reason: Corrected 256 to 254
The T-98 you have is for the First Generation F4-F6 trucks. Many users seek this transmission out as a drop in to replace their crashbox. This is not to be confused with other T-98 variants.
However, the T98 was never offered and will not drop in to an F1 without some serious adjustments to the frame and whatnot:
Lastly, a F6 wouldn't have a 256 - I believe you mean an inline 6 254. For both the engine and transmission - don't scrap them - make sure they find good homes.
The T-98 you have is for the First Generation F4-F6 trucks. Many users seek this transmission out as a drop in to replace their crashbox. This is not to be confused with other T-98 variants.
However, the T98 was never offered and will not drop in to an F1 without some serious adjustments to the frame and whatnot:
Lastly, a F6 wouldn't have a 256 - I believe you mean an inline 6 254. For both the engine and transmission - don't scrap them - make sure they find good homes.
If I’m going through all that might as well use my T5 and fit it as time and ambition allow. I’m keeping the 254, if or when the 239 needs replaced that’s what I’m putting in. I have the plugs installed by hand and spray a bit of oil in the cylinder periodically. Garage is also heated and dehumidified.
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