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My 1981 Auto to Ford V6 T5 Transmission Conversion

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My 1981 Auto to Ford V6 T5 Transmission Conversion

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Old 01-08-2016, 05:53 PM
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Zero1Niner
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Default My 1981 Auto to Ford V6 T5 Transmission Conversion

I know the T5 conversions have been done to death, but I haven’t come across someone that has done exactly this conversion, so thought it might be of interest to someone at some point, so here it goes.

I have a 1981 automatic. A few years back, I decided that eventually I would do a manual conversion. Wasn’t sure if I was capable of doing the job or not, and since most have indicated the clutch pedal assembly was the hardest part of the job, I decided to tackle that first. Found the pedals and installed them, as well as a hydraulic master from an 85 chevy truck back in 2013 (here is a thread I did on the install).

That job wasn’t quite as bad as I expected (but it wasn’t easy). However getting through that, I realized Im pretty sure I can take this on.

Life is busy, and these things always take longer for me than I would like. The original plan was to do an LS1/T56 conversion (still is the plan, but later), but seeing thats a much bigger project and I have not come across a donor car I like enough--and can afford, I decided to take this smaller step first. The engine I have now, although a performance dog, runs reasonably well.

In 2015 I started reading Retro78's and Norval's threads as well as anything else I could find, and started looking for T5 transmissions. Since this is only an interim solution until I find the right LS1/T56, budget was/is really important. I came across a Ford T5 from a 95-97 Mustang V6 for an amazing deal, so I bought it figuring I could sell it later if I dont use it. Ive had it sitting in the garage for 8 months or so now, and decided Im just going to give it a shot and see what happens.

The trans I picked up is a 1352-238, which is a world class, but from a V6 as mentioned. The 94+ ford T5s have an input shaft length that is 7.85", which makes this transmission 1-1/8” longer than a normal Chevy manual trans. Retro78, norval and others have used 2 adapter plates (one 1/2” plate and one 5/8” plate) which is my plan to replicate what they did.

Here are a few shots of the transmission. The bellhousing that is on the shot here is the original Ford bellhousing.
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Old 01-08-2016, 06:31 PM
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Last night I found a listing for a chevy bell housing, pressure plate, clutch, fork and bearing for $75. The guy didn’t know much about it, so again I figured I would grab it up and sell it if it doesn’t work out.

Its a Chevy bolt pattern, and has a number of 3251268 part number. Did a little googling, and looks like it will bolt to the SBC motor, and oddly enough, it has a Ford T5 bolt pattern also. Someone mentioned in one post that I found on another forum that this bell is 3/8” deeper than a standard Chevy bell housing. I measured 6 5/8” (see pic). Are standard Chevy bellhousings 6-1/4”?

If that is true, does my adapter plate need to be a 3/4” single plate instead of 2 totaling 1-1/8”?

I checked the bolt pattern, and looks like the pattern is the same from the bell to the transmission. The center hole is a hair smaller than the t5’s collar, but Im guessing that shouldn’t matter since I will be making the adapter plate (right?).

The clutch that came with the bellhousing fits perfectly on the input shaft, as well as the throwout bearing (am I calling that the right name?) fits perfectly on the shaft.

Here are pics of the bell and what I have collected so far.
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Old 01-08-2016, 06:41 PM
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Here are a few more pics.
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Old 01-08-2016, 07:13 PM
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You have certainly tackled a big job and I hope the end result is worth the time and expense.
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Old 01-08-2016, 07:19 PM
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Id LOVE to see this happen, as Ford transmissions are a dime a dozen on Ebay.
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Old 01-08-2016, 10:45 PM
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Originally Posted by Scottd View Post
Id LOVE to see this happen, as Ford transmissions are a dime a dozen on Ebay.
Absolutely. If this works out, it would really lower the cost for guys that just want a 5 speed that dont intend on beating on the car for cheap.
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Old 01-08-2016, 10:52 PM
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If anyone can help me answer a few questions, Id greatly appreciate it.

Are standard Chevy bellhousings 6-1/4”?

If so, and my bell housing is 6-5/8", then should my adapter plate be one 3/4” single plate instead of 2 totaling 1-1/8”?

I would really like to understand this better. Once the bellhousing is mounted to the transmission, is there a certain length the input shaft should extend past the bellhousing where it meets the engine?

My bellhousing does not have an adjustable pivot screw. Is that something that I really need to get this working correctly?

Thanks for the help in sorting this out.
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Old 01-08-2016, 10:56 PM
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Im putting together a list of the remaining parts i need.

- Hydraulic slave
- Hydraulic fluid reservoir
- Hydraulic lines
- Fabricate bracket for the hydraulic slave
- The spacer adapter
- Flywheel
- Pivot bearing
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Old 01-10-2016, 09:05 AM
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First off, congrats on finding a GM SBC/BBC bell with the ford bolt pattern. Gm did this on some trans with both a GM and Ford bolt pattern bosses on the trans (4.3 Astro vans also had this). If you look inside the bell you can see the GM bosses undrilled.
Since it's an oddball V6 trans, things may be different from the Mustang V8 trans, so things to check.
GM had 10 spline 1 1/8" splines, Ford typically 10 spline 1 1/6" spline inputs. So although the disk will go on, it may not be tight and fit correctly. Get a Ford disk to compare.
The pilot bearing diameter on GM is 0.59" vs 0.668 for ford. You'll need an adapter bushing. Check Novak Adapters for one.
The input shaft length on GM is 6.66, ford is 7.18. The GM 621 bell is 6.29" deep. But before you decide on an adapter depth, you'll need a couple measurements. The input shaft needs to be well seated in the pilot bearing, preferably the full depth, but without bottoming out on the area of the shaft where it expands to the splines.
You also need to check that the disk is adequately seated on the splines while seated on the flywheel without running off the end of the splines or butting against the bearing retainer.
As for the clutch, you can go with the mechanical setup if you want too. The link below has good info on throwout bearing/fork geometry.
BTW, I went through some of this when adapting a Muncie/T10 to an LS motor.
http://www.novak-adapt.com/knowledge/clutches-etc/

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Old 01-10-2016, 01:52 PM
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Bell housing looks like Jeep 2.5L bell. Same bell bolt pattern as sbc but they used ford t5 trans pattern cases. If I remember right have to use 153 tooth flywheel and clutch fork enters bell at different angle. I think this bell also clocks the trans straight up. Don't know if 94 up t5 has straight mount pad or not but do know that 93 back ford t5 had angled mount pad to compensate for the 7 degree clocking. McCloed's has adapter pilot. Need an adapter to go from ford electric vss to gm mechanical speedo. Forte's can help with that.
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Old 01-10-2016, 07:02 PM
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Zero1niner... I think you and I exchanged emails awhile back. I'm in the middle of installing a Mustang Cobra T5 behind my 350. I'm test fitting mine now. First try we almost got it fully seated but about a 1/2" short. Had to clearance the cutout on the tranny tunnel a bit more. Hope to try again to seat the tranny to the engine this weekend.

IM me with any questions you have.
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Old 01-11-2016, 12:43 PM
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Originally Posted by Garys 68 View Post
First off, congrats on finding a GM SBC/BBC bell with the ford bolt pattern. Gm did this on some trans with both a GM and Ford bolt pattern bosses on the trans (4.3 Astro vans also had this). If you look inside the bell you can see the GM bosses undrilled.
Since it's an oddball V6 trans, things may be different from the Mustang V8 trans, so things to check.
GM had 10 spline 1 1/8" splines, Ford typically 10 spline 1 1/6" spline inputs. So although the disk will go on, it may not be tight and fit correctly. Get a Ford disk to compare.
The pilot bearing diameter on GM is 0.59" vs 0.668 for ford. You'll need an adapter bushing. Check Novak Adapters for one.
The input shaft length on GM is 6.66, ford is 7.18. The GM 621 bell is 6.29" deep. But before you decide on an adapter depth, you'll need a couple measurements. The input shaft needs to be well seated in the pilot bearing, preferably the full depth, but without bottoming out on the area of the shaft where it expands to the splines.
You also need to check that the disk is adequately seated on the splines while seated on the flywheel without running off the end of the splines or butting against the bearing retainer.
As for the clutch, you can go with the mechanical setup if you want too. The link below has good info on throwout bearing/fork geometry.
BTW, I went through some of this when adapting a Muncie/T10 to an LS motor.
http://www.novak-adapt.com/knowledge/clutches-etc/
Hey Gary. Thanks for the great information. That Novak read is excellent.

The guy I bought it from wasnt sure what the bellhousing came off of, but from doing the research, its looking like it might be the infamous 'iron duke' bellhousing that came off of a 151 80's jeep.

You're right about the splines. I took a bunch of measurements (pics below). The clutch I have (which Im not sure what it was from) does fit the shaft, and 'feels' tight, but I will be picking up a food clutch.

The pressure plate and clutch that came with the bellhousing, the clutch disk is only ~9-1/8". Im guessing that those 2 pcs will not be able to be used, and i will need to use the 11" clutch, is that right?

For the clutch, Im planning on using the slave hydraulic cylinder if I can since I already have the hydraulic master cylinder from an 85 chevy pickup installed. Im a little unclear on this particular fork setup. There is no adjustable pivot for the fork. Still learning on how this did/should work.

Thanks for the help on figuring out the correct spacer.
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Old 01-11-2016, 12:47 PM
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Originally Posted by 68blvert View Post
Bell housing looks like Jeep 2.5L bell. Same bell bolt pattern as sbc but they used ford t5 trans pattern cases. If I remember right have to use 153 tooth flywheel and clutch fork enters bell at different angle. I think this bell also clocks the trans straight up. Don't know if 94 up t5 has straight mount pad or not but do know that 93 back ford t5 had angled mount pad to compensate for the 7 degree clocking. McCloed's has adapter pilot. Need an adapter to go from ford electric vss to gm mechanical speedo. Forte's can help with that.
Hey 68blvert,

I think you're right about the jeep, and from what I have read, I think you're also right about the 153 tooth flywheel.

Im still not clear on the angle for the fork, but when I loosely fit the bell to the housing, it seemed to align the trans straight up.

I didnt realize that this trans was electric speedo. I was planning on opening the trans up to at the very least inspect before I put it in. Can/should that speedo mechanism be changed to a mechanical version if its opened?
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Old 01-11-2016, 12:49 PM
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Originally Posted by Frankenvette View Post
Zero1niner... I think you and I exchanged emails awhile back. I'm in the middle of installing a Mustang Cobra T5 behind my 350. I'm test fitting mine now. First try we almost got it fully seated but about a 1/2" short. Had to clearance the cutout on the tranny tunnel a bit more. Hope to try again to seat the tranny to the engine this weekend.

IM me with any questions you have.
Hey Jim! Yes! Thank you very much for all of your information. That was really helpful stuff.

Do you have a thread of your install? If not, why not?? Dont hide that experience from us!
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Old 01-11-2016, 12:53 PM
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Here is the clutch and pressure plate that came with the bellhousing. Guessing these are unusable, but not sure.
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Old 01-11-2016, 01:04 PM
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Not sure an 11" clutch/pressure plate will fit on a 153 tooth flywheel. They're generally on 168 tooth. And fitting an 11" clutch/PP probably wont fit in that bell. I suspect you'll need to find a ford disk that will fit your existing flywheel, 10.5" clutch.

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Old 01-11-2016, 05:45 PM
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Originally Posted by Zero1Niner View Post
Can/should that speedo mechanism be changed to a mechanical version if its opened?
You can buy an adapter to convert to mechanical. Let me know if you need the vendor. I've got the part in my garage waiting to be installed.
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Old 01-12-2016, 01:39 PM
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Hey, just looking at the dimensions on your disk. 153 tooth flywheel uses a 10 1/2" clutch. Yours looks smaller.
You should determine if a SBC 153 tooth flywheel, 10 1/2" clutch/pressure plate, and GM starter will fit with that bell.
Even though it has the chevy bolt pattern, the housing may fit the jeep flywheel/clutch, it may be too small for standard GM stuff.

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Old 01-12-2016, 10:23 PM
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Originally Posted by Garys 68 View Post
Hey, just looking at the dimensions on your disk. 153 tooth flywheel uses a 10 1/2" clutch. Yours looks smaller.
You should determine if a SBC 153 tooth flywheel, 10 1/2" clutch/pressure plate, and GM starter will fit with that bell.
Even though it has the chevy bolt pattern, the housing may fit the jeep flywheel/clutch, it may be too small for standard GM stuff.
Yep. Mine is much smaller. In everything that I have read, it seems that it will fit the 153 tooth flywheel and 10.5" clutch/pressure plate.

Regarding the starter. I was/am concerned about that. I have read that I might need to get a 'mini' starter to fit, but also have read where someone is using a standard starter with this bellhousing.

Among others, here is one link/excerpt from another forum that I found that lead me to think this stuff will fit.

From tators on Pirate4x4.com He was using a T18 transmission, but there is still a bunch of relevant info in his post that caries over to my T5.
Bellhousing - 81' CJ with GM 151 Iron Duke engine -same pattern as the SBC.

Flywheel - GM 153 tooth 86&up (non Z28!!) Centerforce PN# CF700170 ,
If shopping for a used flywheel 86-92 camaro with 305 is the application. the later years use a different flywheel and it won't work (trust me, I bought one on ebay and it interfered with the clutch arm), 168 tooth won't work because it won't fit inside the bellhousing..

Clutch Disk - since the t18 was mostly used in fords... An early 90's Mustang 5.0 clutch disk works.. The t18's input shaft is 1 1/16 10 spline, the same as the T5 used in mustangs.. (10.5 in clutch), Centerforce PN# 381021

Pressure Plate - Camaro 86-92 305 engine, or Centerforce PN# CFT360056

Release Arm - use the stock arm and pivet from the 151 bellhousing.

Throwout bearing - stock 151 application for diaphram type clutch.

Pilot Busing - order one from Novak or Adavanced Adapters... I spend alot of time looking for an OEM bushng that would work but couldn't find one... TIP*** test fit the bushing on your trans input shaft before hammering into your crank...(sometimes they send the wrong one!!! )

Starter -- I have read online that this setup would require a GM mini starter... (about $150) for driveshaft clearance I suppose...
I am running an 86 camaro normal starter (about $35) and it seems to be working with my setup
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Old 01-12-2016, 10:36 PM
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Not sure if anyone knows Sly Vette on this forum, but he mentioned the jeep 'iron duke' bellhousing (which is basically what this is) on a very old thread, but looks like he hasnt been on here for a few years. Does anyone know if he is still around? I was hoping to pick his brain on this.

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