Synchro Four Speed Swap


IHC in the early to mid-fifties.

Golden Jubilee
Golden Jubilee

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Joined: Wed Sep 05, 2018 1:50 pm

Location: Northern New Mexico

Post Fri Jul 12, 2019 8:45 pm

Synchro Four Speed Swap

I must be getting old but I don't enjoy double clutching crash box transmissions as much as I used to so I am starting to look for a synchronized four speed to put in its place. I'm assuming it has to be IH and two wheel drive but what year trucks should I be looking for if I'm in the junkyard?

Besides the Warner T19 models I believe there is a T98, does that fit and is it a good choice? Do parts still exist for these tranny's if I find one that needs a rebuild? Any information given on this subject will be greatly appreciated.
56 S120 4x4,

Yard Art
Yard Art

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Joined: Mon Jan 14, 2013 3:56 am

Location: Beaverton, OR

Post Sat Jul 13, 2019 9:40 am

Re: Synchro Four Speed Swap

If my memory serves me correct, the T98 will fit, but it is longer so it will require driveshaft modification. I am pretty certain that if you get a T98 from an international truck it should bolt up to the bell housing and all of the clutch stuff should work.

As a disclaimer, I have never made this swap. I was considering it for my S132 at one point and the need to modify the driveshaft stopped me. I enjoy my S132 as it is. However, I do not drive it too often, and I do understand the desire to add a synro transmission.
56 S-120 4x4 started the whole mess.
S-132 dually longbed,
S-120 4x4 Travelall,
S144 Forestry truck,
S160 Holmes tow
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Golden Jubilee
Golden Jubilee

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Joined: Thu Nov 29, 2012 11:47 am

Location: Bothell, Washington

Post Sat Jul 13, 2019 2:48 pm

Re: Synchro Four Speed Swap

^^^yup^^

T-98 from newer IHC truck will bolt right in, may need to shorten driveline, but splines, shaft length, bolts all the same,

I did this in a few KB trucks, made all the difference,,,,,
Gentle Men! you can't fight in here! This is the war room!
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Golden Jubilee
Golden Jubilee

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Joined: Mon Sep 07, 2015 11:14 am

Post Sat Jul 13, 2019 3:38 pm

Re: Synchro Four Speed Swap

Harvey has the T98 transmission , love it, smooth shifting every time.

Shifts darn near as nice as my 5 speed dodge cumins ..
$ 75.00 or Best offer , No rush to sell.
Thanks for Looking , - SM
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Golden Jubilee
Golden Jubilee

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Joined: Sat Dec 01, 2012 9:55 am

Post Sat Jul 13, 2019 5:32 pm

Re: Synchro Four Speed Swap

The T-98 is a lot easier to swap in than a T-19. Other than driveshaft length, the T-98 is a direct bolt-in. Both will bolt up to the bellhousing with the same input shaft diameters and splines. But the T-19 has a shorter input bearing retainer (the sleeve the throwout bearing slides on) that would have to be replaced with one from a T-98, and then the groove inside the retainer is deeper for a T-98 because it has a spacer behind the snap ring. And if you have the transmission mounted parking brake, and want to keep that, you would have to replace the rear bearing retainer, plugging one hole and drilling and tapping another, and then drill and tap holes on the side of the case for the linkage and lever. And then the lever will be about an inch forward of where it is on the T-98/T-9. And still would probably have to shorten the driveshaft. Swapping in a T-19 would pretty much require a T-98 for parts. On the other hand, a T-19A close ratio would give you 4 gears synchronized, without a granny gear, and better spacing between 3rd and 4th.

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