I’ve got a T5 in my 66 with a 3:55 open diff. I’ve been very happy with it. The car is street driven only.

I started with a C-code/3-speed.  2.79 open rear.  worked fine thru a couple of NY winters. Chains helped a lot.

Somewhere around 1970 I moved to a 3.25.  Still open diff.  I loved it but it reduced my mpg by about 3mpg.  Telling when driving upwards of 30,000/yr.

Sometime later I returned to a 2.80 open (don't remember when).

1989 In went the 351w w/Toploader.  My mechanic had a brand new 3.00 open vs the worn out 2.80. Had to put it in.  Has worked just fine with all the low-end power that I need.  I no longer play drag racer.  Give me power to get up to speed when entering a freeway and passing someone when safe.  I prefer mid range acceleration.

Around 2000 I installed a wide ratio T5.  For my liking first is too low.  Shifting comes too soon.  I would prefer the 2.95 first gear.  Even with the 3.00 rear the car has plenty of pickup.  I can lay 2nd gear rubber.

The 351w has a 2.18-2.24 duration, 0.512L retro roller cam, ported iron heads, and FITEC FI. The cam is said to have a 1500-5000 rpm range.

To date I have never had a need for limited slip diffs.  In Calif it does not rain enough for me to want one.  

And, yes, I have done some 2-tracking with it with ease.

 

Presently the 66 just has the stock 289, and I got way too good of a deal on a 3.35 T5 not to use it. I have the 2.95 T5 in the 68 and it makes first much more useable. My 68 has 3.73 and Trac loc (Explorer 8.8)

I will eventually upgrade the motors in the 66, but for now it just runs too good to mess with. 3.50 probably makes the most sense but I bet I go 3.80.

Still on the fence concerning the diff, even with more motor I just plan to cruise it,

kardad wrote:

Presently the 66 just has the stock 289, and I got way too good of a deal on a 3.35 T5 not to use it. I have the 2.95 T5 in the 68 and it makes first much more useable. My 68 has 3.73 and Trac loc (Explorer 8.8)

I will eventually upgrade the motors in the 66, but for now it just runs too good to mess with. 3.50 probably makes the most sense but I bet I go 3.80.

Still on the fence concerning the diff, even with more motor I just plan to cruise it,

Stock 289 is going to have trouble spinning a 3.80 or anything more than a 3.25.  It will run out of air  real quick.

There are certain thins in life that you can simply never have too much of, and traction is one of them.  IMO, if you are changing the gear ANYWAY, another couple hundred to add a limited slip is a no brainer.  The rear in my '07 F250 work truck is either a worn out traction lock, or open, and I do not hot rod the truck around, but it still sucks in wet, slippery conditions etc. when it spins only the right rear.  I have the old traction lock from my '06 F250 (replaced with a True Track) which I rebuilt with Randy's clutch kit I will eventually install in it. 

My friend's 64 Falcon has the stock 3.25 rear (mountain states DSO) and a 3.35 T5.  It works very well for normal driving and doesn't seem to be too quick to run out of first gear.  I would not think a 3.55 or 3.80 would make me happy with a 3.35 first gear.  My Fox had a 2.95 (T5Z) and 3.73 and it always felt just right to me.

TKOPerformance wrote:

BobE wrote:

I have a T5 w/2.95 first gear, 9” w/Auburn LSD, 225/60x15” tires.  I recently went from 3.89 to 3.70’s.  I now think a better choice would have been 3.50’s, as taking off in first gear still is a quick shift to second.  Plus, the 3.50’s would be better for highway cruising.   The LSD choice was ‘just because”.

Remember the Z spec gearing was designed for a car that had a 6,250RPM redline and assumed you were running 3.73 gears.
 

My T5 is a WC model, but point taken. 
 

Old stock 66   3:00:1gear (one-tire-on-fire) with a WC  T-5.
"Everybody sez".... "dat mow-der would really come alive if'n ye hadda dab more gear and a Trac-Loc behind it !"  BUTT........it's ran great just like it is so why change what-works-good ?!
6sally6

Eaton tru trac with 3.55

BobE wrote:

TKOPerformance wrote:

BobE wrote:

My T5 is a WC model, but point taken. 
 

If its has a 2.95:first it's either a Z-spec, or was converted to the Z-spec gears (you used to be able to buy the kit for $450, but not anymore).  The only production Ford T5 that had a 2.95 first were in '83-'84 which were NWC.  4 cylinder T5s had numerically higher 1st gears than the V8s, later V6 cars used the 3.35 first, and the much later V6s had a numerically higher first gear.  GM had a T5 that was a WC 2.95 first, but they were only used in select 3rd gen F-bodies and are rotated 22 degree due to the F-body rear suspension setup which mounted the front of the torque arm to the tail of the transmission, and the mounting bolt pattern is different than a Ford.  I'm sure it could be made to work, but I highly doubt anyone ever swapped a GM T5 into a Ford since the WC V8 Ford T5s are 20x more common than the GM ones.  You could run factory GM gears in a Ford case though,so long as you used a Ford input shaft (I built a half dozen GM WC T5s with Z-spec gears and a GM input shaft). 
 

I purchased this T5 new, in 2007, that was part of the complete conversion kit for my 65 Mustang.  This trans is listed as “aftermarket Ford”; the Tremec part is number is 1352-000-251, called "WC", and listed for a 5.0 engine.  I do not believe that it was ever installed in a production car,  If you send me your email address I'll forward the Tremec data sheet that lists many of the Tremec transmissions. 

 

Z-Spec, Aftermarket, Heavy Duty, etc. (all of which are WC)  All BW/Tremec/Ford speak for the same thing.  WC was just to distinguish the later transmissions from the earlier ones.  The NWC was rated at a lower torque spec (265 vs 300 for the WC I believe).  The primary difference was the NWC still used brass synchros and used torrington bearings/thrust washers instead of tapered roller bearings.  They ran different fluid too, but the NWC don't use heavy weight gear oil like some believe, they originally came with Dextron II, which is NLA, so now Tremec specs 50 weight gear oil.  All WC T5s used ATF. 

No 2.95 first geared T5 was ever factory installed in a Ford.  There used to be a couple part numbers based on application I believe (Ford, GM, input shaft spline count 10 vs 26), and at one point you had the option to go with a 0.63 or 0.70 5th.  Now there's only one still sold (part number 1352-000-251) which is a 2.95/1.94/1.34/1.00/0,63 with a 10 spline input and 28 spline output. 
 

351W, 4R70W, 9" Trak-loc 3.25 ratio.

TKOPerformance wrote:

BobE wrote:

TKOPerformance wrote:

If its has a 2.95:first it's either a Z-spec, or was converted to the Z-spec gears (you used to be able to buy the kit for $450, but not anymore).  The only production Ford T5 that had a 2.95 first were in '83-'84 which were NWC.  4 cylinder T5s had numerically higher 1st gears than the V8s, later V6 cars used the 3.35 first, and the much later V6s had a numerically higher first gear.  GM had a T5 that was a WC 2.95 first, but they were only used in select 3rd gen F-bodies and are rotated 22 degree due to the F-body rear suspension setup which mounted the front of the torque arm to the tail of the transmission, and the mounting bolt pattern is different than a Ford.  I'm sure it could be made to work, but I highly doubt anyone ever swapped a GM T5 into a Ford since the WC V8 Ford T5s are 20x more common than the GM ones.  You could run factory GM gears in a Ford case though,so long as you used a Ford input shaft (I built a half dozen GM WC T5s with Z-spec gears and a GM input shaft). 
 

I purchased this T5 new, in 2007, that was part of the complete conversion kit for my 65 Mustang.  This trans is listed as “aftermarket Ford”; the Tremec part is number is 1352-000-251, called "WC", and listed for a 5.0 engine.  I do not believe that it was ever installed in a production car,  If you send me your email address I'll forward the Tremec data sheet that lists many of the Tremec transmissions. 

 

Z-Spec, Aftermarket, Heavy Duty, etc. (all of which are WC)  All BW/Tremec/Ford speak for the same thing.  WC was just to distinguish the later transmissions from the earlier ones.  The NWC was rated at a lower torque spec (265 vs 300 for the WC I believe).  The primary difference was the NWC still used brass synchros and used torrington bearings/thrust washers instead of tapered roller bearings.  They ran different fluid too, but the NWC don't use heavy weight gear oil like some believe, they originally came with Dextron II, which is NLA, so now Tremec specs 50 weight gear oil.  All WC T5s used ATF. 

No 2.95 first geared T5 was ever factory installed in a Ford.  There used to be a couple part numbers based on application I believe (Ford, GM, input shaft spline count 10 vs 26), and at one point you had the option to go with a 0.63 or 0.70 5th.  Now there's only one still sold (part number 1352-000-251) which is a 2.95/1.94/1.34/1.00/0,63 with a 10 spline input and 28 spline output. 
 

Ahh, OK, I was just stating the details of the T5 model that I installed.