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GM T5 fitment

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GM T5 fitment

Post #1 by StarDiero75 » Mon Jan 14, 2019 2:37 am

Howdy guys,

I'm able to get a good working GM T5 for $200 and I want to make sure I can make it work in my 65 Ranchero. I will need to put the S10 tail shaft on it, but that should be easy since I wont have to mess with the slightly different Ford and GM stuff put together.

So should this work in my Ranch, can I use a Ford clutch or is the input shaft splined differently? Will the adapter from moderndriveline fit between the 2? Should I just call Moderndriveline and have this entire conversation with them instead since Im sure they've heard this before?

Here's the numbers on the tranny:

What can you all tell me about if from the numbers? I'm completely unfamiliar with these trannys but i know I want it in my car lol.

Thanks guys,
--1965 Ranchero w/1966 200, dual friction diaphram 9" Modern Driveline clutch and billet flywheel all balanced, 1985 SVO WC T5 with front shift, 1966 2.8 Ford 8", 2V converted built 1980 head, Autolite 2100 1.08, Dual out VI headers, Custom curved DUI, 256H Schneider cam 2.5 degrees advanced with dual roller chain, 2" exhaust with H pipe and Flowmaster 40s
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Re: GM T5 fitment

Post #2 by rocklord » Mon Jan 14, 2019 8:51 am

Does the T-5 have a tag on it starting with 1352-xxx? The last three numbers (xxx) will tell you what vehicle the transmission is from, and the
gearing. Here's a website that has a partial list of T-5s: ... d-tags.htm
Here's a website that will tell you what vehicle a T-5 is from if you have the tag number:

As for using a GM T-5 in a Falcon, check out and click on "7-25-03 Falcon Transmission Updates".
Rick goes through what parts and machining is required.

Hope this helps.

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Re: GM T5 fitment

Post #3 by 62Cometman » Mon Jan 14, 2019 10:39 am

To answer one of your questions in short, the GM T-5 applications traditionally came with 28 spline input shafts. As stated above rick site and post list options for swaps using mercedes and alfa based clutch discs with the factory style pressure plate and flywheels. This would be a good option, as the ford based units us the Large ford 10 spline like what the v8 units got and i havent found anyone that offers the clutch disc small enough to be used with pressure plate or flywheel. In any case good luck!
1962 Mercury Comet 170 ci, Dagenham Trans, 2.83:1 7.25 rear.
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Re: GM T5 fitment

Post #4 by rickwrench » Sun Jan 27, 2019 5:15 pm

GM v8 T-5s have 28 spline inputs shafts, v6 have 14. Finding a small enough 28 spline clutch is a tough job (custom, $$$). 14 spline clutches are common/RockAuto items. Be aware that GM switched from the "Muncie" to "Ford" pattern on their T5s somewhere along the line (can't remember when, offhand).

World Class (WC) vs. non-World Class (NWC):
Check the countershaft bearing, stamped shell = NWC, machined = WC. This makes a difference as to what oil is used. Synchros are also different, but lined WC synchros work fine with both types of oil. The reason for different oils is that the tiny roller bearings on WC T5s are inadequately oiled when using thick 70-90wt oil. BW kinda forgot to address oiling when they added shaft bearings to the design, to increase torque capacity. Heavy oil gets in there, but doesn't flow through the race very well. Gets hot, breaks down, toasts those needle bearings. Thin auto tranny fluid flows right in though the race, keeps them properly lubed. NWC T5 doesn't have needle bearings on the shaft to worry about, so thick oil is fine. That's the only real difference.

Which is better? Both are excellent I6 transmissions. WC may be -very slightly- smoother to shift, NWC is cake to rebuild. Literally a 45 minute job. Be careful ordering parts - 80% of the vendors don't really know the difference. Will happily sell you a lot of wrong parts. I'm using a NWC right now in the Squire. At stock(ish) 200 I6 85rwhp, torque capacity is a non-issue. Both versions shift 100x better than any other Ford transmission used on the I6.

To use a Muncie pattern GM T5 on a "8-1/2" small bell" 200/170/144, you start with an Econoline bell. Not common but they are around. And then a Muncie to toploader adapter, also not common, but available. This spaces everything out just right.

T5's are mostly a "parts is parts" transmission. Lots of bits swap easy, some do not...

Early GM S10 T5's often had a 3.76 1st, some had a 4.00. Both work nice with a small I6, though the 3.76 is my preference. Early T5 V6 Camaro used a 3.50 first w/ a 14 spline input.
The overdrive gears (S10 = 0.72) makes the falcons drivable at modern highway speeds. 3.00 is a nice cruise speed rear end ratio for this combo. Good MPG/power balance. 3.50 runs higher, but acceptable, RPMs. Also 3.50 rear usually won't lug on most hills, and lets you run most grades without downshifting.
I've done cross country road trips in both configurations. 3.00 was cheaper on gas, 3.50 was a lot less shifting in the mountains.

Other parts needed: Input shaft bushing (use bronze, custom size), T/O bearing, correct size slip-yoke seal, speedo gear/cable adapter, rear transmission mount.

Other than clearancing the flywheel, don't take any weight off of it. Light flywheels are great for racing, but SUCK to daily drive.

Direct link to the old page in question:
Squire T5 page

Hey Mods - There used to be a bunch of stickied tech posts that covered a lot of this, but they seem to be long gone.

'62 Falcon Wagons (x2), Kellison J5, V8 Alfa GTam, Corvair Corsa:

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Re: GM T5 fitment

Post #5 by bubba22349 » Sun Jan 27, 2019 8:40 pm

The tech section that has all this info was moved, it's at the very top of the forums it's the section that's called "General Tech : Read Only". See link below for one of them. Good luck :thumbup: :nod:

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I am hunting for a cheap project car to build up. My Ex-Fleet of Sixes sadly these are all long gone! :bang: 1954 Customline 223 3 speed with O/D, 1963 Fairlane project drag car with BB6, 1977 Maverick 250 with C4, 1994 F-150 a 300 with 5 speed.

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