Close



Results 1 to 14 of 14
  1. #1
    FEP Supporter
    qikgts's Avatar
    Join Date
    Jan 2010
    Location
    Rockledge, FL
    Posts
    1,458

    Default How much power have you put through your T5, 10 inch clutch, and 7.5 rear?

    ... and how did you drive/use it?

    I just picked up a set of FPP X307 heads with the 58cc chamber and I'm planning on using them with a Weiand X-CELerator 7515 on my otherwise stock '85 roller shortblock. I still have my T5 and 10" clutch along with the 7.5" rear in the car. Pretty much decided that if I cam it I'll use a TFS Stage 1 that's collecting dust right now. I have zero intention on making any drag strip passes, power-shifting, or running sticky tires. I might even keep the 2.73's, just cause. Total street cruiser. Maybe I'll try to carve some cones once or twice to see what it's like but this car is really going to stay 99.95% non flat out aggressively driven for the rest of it's foreseeable life with me.

    Previously I had a '95 GTS. I broke two T5's and one was big dollar unit that made exactly 1 pass and broke in the burnout box before the second run. Whatever... It stung, but that car ultimately got a Tremec 3550, CF Dual Friction, and the 8.8" rear had a girdle put on. It was drag raced a bunch both 1/4 and 1/8 with 150 shot lighting off in second gear (only 1/8 mile on the sauce) and all the drive-train stuff held up great with ET Streets and BFG Drag Radials. However I never left at anything more than 3200 RPM and that was with plenty of left foot modulation. I know how abuse will break stuff. This question isn't about that kind of application.

    So, how have you made out with around 270-290 HP and 290-320 TQ to the ground with stock 4 eyed running gear? How did you drive yours? Love to hear your experiences.
    '85 GT

  2. #2
    FEP Super Member mmb617's Avatar
    Join Date
    May 2005
    Location
    Altoona, PA
    Posts
    4,249

    Default

    I can only answer 1/3 of your question as I have an ungraded clutch and rear but I did bracket race for 7 years with nearly stock T5's. The only mods were a steel front bearing retainer, cluster support plate and I always shimmed them tight. I also made sure I only used genuine Tremec parts when they needed rebuilt. There's a lot of no name parts out there that aren't worth buying.

    I think the T5's have gotten a bum rap and they can be stronger than people think. The one thing I found out early on is they will not tolerate power shifting, but if you avoid that they hold up well for what they are. I have about 400 hp to the wheels and left the line at 3300-3900 off the two step with sticky tires. I averaged about one broken transmission a year but I raced every Friday night so each transmission put up with that abuse for hundreds of passes before failing.

    Now that I've retired from racing and put street tires on my car all I do is drive it around town and to cruise-ins. I'm so confident that I won't have any transmission problems that I gave my spare T5 to my son as he's building a '67 Mustang that he bought minus drivetrain.

    I can't see any reason you'd have problems with your intended usage. Well, I can't speak to how it would hold up to running the cones as I've never done that, but for non-aggressive street driving I'm sure you'll be fine.
    408/T5/3.73's

    We're not fast racers, we're more what's known as half fast racers.

  3. #3

    Default

    I agree that the T5's and 7.5's are probably stronger than most give them credit for.

    My T5 and 7.5 held up to my teenage shenanigans behind the stock engine just fine, though I think the 10" clutch was the weak link. Mine was slipping even at stock power levels.

    That same T5 is now behind my 347 and seems to be hanging in there just fine, but I did install a steel bearing retainer and cluster support plate for the insurance. I can't attest to how a 10" clutch and 7.5 would hold up as those got upgraded for the 10.5" clutch and an 8.8.

    All my driving is on the street on street tires.

    As mmb617 said above, I think you'll be fine with what you have planned.
    Thomas

    1985 Mustang GT - Build Thread
    347 (Stock Block, Scat Crank & Rods, Probe Pistons, 11:1 CR, AFR 185's, PP Crosswind Intake, Custom-ground Comp Hyd Roller Cam, Scorpion 1.6 Roller Rockers, Holley 3310-4), T-5, 8.8 w/3.55's, MM SFC's, T/A, PHB, LCA's, Strut Tower Brace, K-Member Brace, Bilstein HD Struts/Shocks, MM/H&R Springs, SN95 5-Lug, Cobra Brakes, '04 Mach 1 Steering Rack

  4. #4
    Venomous Moderator Hissing Cobra's Avatar
    Join Date
    May 2002
    Location
    Wareham, Massachusetts
    Posts
    9,720

    Default

    When I put my Cobra on the road back in 2004, I installed a brand new Tremec 3550 to go along with my 306 (307 rwhp/278 rwt). What a POS that thing was! For the first two years it was "hit or miss" as to whether or not you could shift into 3rd gear at 6,500 rpms. It was not good for racing, as I needed to shift at that rpm because my 306 made peak power at 6,400 rpms. On the runs I'd get it into 3rd, I'd be in the mid 12's @ 108 and on the runs I couldn't, I'd be in the mid to high 13's @ 100 mph. It sucked! After two years of this madness, I took it out and replaced it with a rebuilt T-5 that we installed a steel bearing retainer onto. Wow! What a difference! No more missed gears and mid to high 12's all day long.

    That transmission was in the car for 8 years and in 2014, I installed my 347 stroker motor that made 420/380 at the wheels. Boom! Instant 11's @ 116-121. The tranny held up excellent until the summer of 2018, when I blew 3rd gear at the track. When I went into 3rd, the shifter felt "funny" and when I let the clutch out BOOOM! Not fun, but it is what it is.

    To recap, I had the T-5 in the car for 10 years with over 120 passes on it before it broke. I replaced it with the T-5 that I had from my '89 LX 5.0/5-speed. We swapped over the steel bearing retainer and the shifter, and called it a day. It's been in the car for the past two summers without any issues and that includes another 20 passes with the stroker motor.

    I know I'm on borrowed time with it and I've been looking for alternatives but I'll need to spend about $5,000 to get the one that I really want (TR-3650). Someday I will get one of those, it's only a matter of time.

    As for the 7.5" rearend? I wouldn't even bother with one of those.
    Last edited by Hissing Cobra; 07-20-2020 at 05:33 AM.
    Pete Slaney

    1979 Mustang Cobra

    347/T-5/4.30's
    420 rwhp/380 rwt (New Motor)
    11.49 @ 121.86

    306/T-5/4.30's (Old Motor)
    307 rwhp/278 rwt
    12.38 @ 111.38

  5. #5
    FEP Senior Member
    Join Date
    Dec 2016
    Location
    Grand Rapids, MI
    Posts
    721

    Default

    Quote Originally Posted by Hissing Cobra View Post
    I know I'm on borrowed time with it and I've been looking for alternatives but I'll need to spend about $5,000 to get the one that I really want (TR-3650). Someday I will get one of those, it's only a matter of time.
    TR-3650? Please explain. These don't seem to get much more love than the T-45 which doesn't seem to get much love at all.
    '89 XR-7 5 Speed
    '95 SC 5 Speed
    '91 Crown Vic P72 351W
    '97 Thunderbird
    '85 Ford LTD Squire

  6. #6
    Venomous Moderator Hissing Cobra's Avatar
    Join Date
    May 2002
    Location
    Wareham, Massachusetts
    Posts
    9,720

    Default

    Quote Originally Posted by KevinVarnes View Post
    TR-3650? Please explain. These don't seem to get much more love than the T-45 which doesn't seem to get much love at all.
    I hate my Tremec 3550 so much, I'm not even going to rebuild it. The TR-3650's shift smooth and can handle a lot more power than the 3550's and the T-5's. G-Force manufactures a custom case without the built in bellhousing and offers a custom plate to bolt to it that will allow it to bold onto a 302/351 block. See the specs on it here.

    https://www.gforcetransmissions.com/tran_3650.asp
    Pete Slaney

    1979 Mustang Cobra

    347/T-5/4.30's
    420 rwhp/380 rwt (New Motor)
    11.49 @ 121.86

    306/T-5/4.30's (Old Motor)
    307 rwhp/278 rwt
    12.38 @ 111.38

  7. #7
    FEP Super Member erratic50's Avatar
    Join Date
    Dec 2016
    Location
    Nebraska
    Posts
    4,575

    Default

    I have in the neighborhood of 300HP and 350 ftlbs at the crank in my 86GT. More for a while when it was being bottle fed anywhere from a 50 to a 100 shot a few decades ago.

    I've always ran the most grippy tires I can find on the street. For the bulk of the miles I've put on my car I was running pretty much the cheapest clutch I could get my hands on with a King Cobra pressure plate that was still alive after the clutch was toast when I somehow manged to spring for one once.

    The car was a daily for 18 years and has been a toy for the past 10. I clubbed the living crap out of it from age 17 to age 35 pretty-much daily. Lots of T5's did not live up to their job, but it saw 2 years at the drag strip every weekend in the early 90's bracket racing and lots of street racing too.

    I have killed a LOT of T5 / T5Z's over the year. I'd have to look at receipts but I think I'm on #8 in my car - could be #9. The car has 1/2 million miles on the original motor which is still absolutely terrorizing everything behind it.

    I'm on my 3rd 8.8 in my car and it candidly it needs its 4th. The 2nd one was still handing in there but I wanted 5 lug but Trey can attest that that 8.8 was on borrowed time when he stripped it down to rebuild it for my 85 project.

    My take on it.... #1 -- ****-can the 7.5. They are a very common failure point and that includes street driven cars what really did not see that much abuse. You are wasting time and money trying to make one hold up decent behind any significant source of power. That's why the 87-88 Turbo coupe had an 8.8 and nearly every SVO I've looked at has been converted. Most 79-85 cars have been swapped to 8.8 by now too and with good reason. Yes-- they are that much better.

    T5 - there are plenty of things you can do to increase the life of a T5 for sure. The transmission guys I've worked with over the years all seem to agree that not having enough power to make the tires burn pretty freely in the next gear is a LOT harder on a T5 than anything high powered with too little tire is.

    Not all T5's are created equal. Look up the tag and know what you have. Certain ones are truly a ticking time bomb. If you haven't blown it out yet, let me at it.... the car doesn't need to have more than around 175 HP to trash the early ones.

    Non-WC units..... not a good starting point. find something else.

    1352-165 and 1352-169 ..... not very good. They only hold 265 ft lbs from the factory while a stock HO that's turned up can easily produce over 300 ft lbs. Time bomb with emphasis on BOMB cuz there's not much time. I've personally had both, neither put up with anything at all for very long before they left me beside the road.

    1352-199 - pretty decent unit. I think its rated at 300 ft lbs, lord knows they will take more if they input shaft is shimmed correctly. One piece steel bearing retainer and a mid-plate, they will hold up to quite a bit of abuse. Mine lasted 150K hard miles including most of the time my car spent at the track bracket racing.

    1352-204 - also a decent unit, again rated at 300. I put a TON of miles on my car with one of these. It was in and out for 4 clutch jobs and finally gave up the ghost with over 200K miles having passed through it.

    1352-201 - not sure how good it was supposed to be, don't remember what it was rated. I bought it with an input shaft problem caused by some idiot not putting the bolts in the tranny - got it for $75. I patched it up with an Astro bearing retainer then proceeded to beat the living crap out of it with a ****-ton of full power shifts .... turned it into a clanking pile of scrap, and sold it as a core for $125 about 10K miles later.

    The numbers escape me on a few of the other WC T5's and T5Z's I've ran, but they didn't last long.

    The unit I'm running now is a 1352-165 that I had tore down and built to T5Z specs. It seems Ok with powershifts at 6150 so far ....


    What to do to make at T5 last

    Get good lower control arms. If there is even the slightest hint of wheel hop it is absolute hell on the transmission and it will cause it to fail prematurely

    Get a light flywheel. think about the inertia of a 30 lb flywheel at 6000 vs a 14 or 17 or 22. Yes you can go too far on the street in terms of lighter flywheel. I do not see a single reason to ever run a flywheel that's heavier than 22 lbs. Autozone sells a 157 tooth 50oz flywheel that works out good. It upgrades you to a 10.5" clutch and it fits behind the factory bellhousing most of the time without issue.

    Get a good clutch but don't go crazy on power rating. The clutch should absorb the hit when you bang gears on the redline. If the springs are too stiff they won't.

    Put in good U joints. Make sure they can be greased. If the slip yoke is worn at all, replace it. Have the shaft balanced to eliminate the slightest hint of vibration because that will kill a T5 quickly.

    Or if possible, run an AL driveshaft. The less rotating mass you have the better off you are.

    Clutch adjustment is key when shifting hard. Make absolutely certain the clutch is releasing properly because if you don't you will damage the T5.

    Get a good shifter with positive stops and adjust them correctly.

    Make absolutely certain the mounts are good. 93 Convertible mounts help with pinion angle and will help a T5 hold up, but a good cross-member and transmission mount are absolutely critical regardless of anything else.

    Avoid super sticky tires or accept that you will kill T5's more often if you run them.

    Use proper fluids. WC T5's originally had Dextron II which is much thicker than Dextron III. Last I looked, Ford and Tremec suggest Mercon 5 or syncromesh.

    If no-one specifically calls it out, I will. DO NOT ever use a teflon additive in a T5. It will eliminate the ability of the synchros to do their job and DESTROY the gearset in short order.

    I agree with what is said above. T5's HATE being powershifting. They will hold up a little longer with less rotating mass in the mix but ultimately they will fail. If you do it, accept that you will go through them faster than you'd like or build something else. A T56, for example.
    Last edited by erratic50; 07-08-2020 at 01:58 AM.

  8. #8
    FEP Member
    Join Date
    Oct 2017
    Location
    south-central WY
    Posts
    251

    Default

    Quote Originally Posted by Hissing Cobra View Post
    I hate my Tremec 3550 so much, I'm not even going to rebuild it. The TR-3650's shift smooth and can handle a lot more power than the 3550's and the T-5's. G-Force manufactures a custom case without the built in bellhousing and offers a custom plate to bolt to it that will allow it to bold onto a 302/351 block. See the specs on it here.

    https://www.gforcetransmissions.com/tran_3650.asp
    Any idea about price?
    Will it work with a cable speedometer?

  9. #9
    Venomous Moderator Hissing Cobra's Avatar
    Join Date
    May 2002
    Location
    Wareham, Massachusetts
    Posts
    9,720

    Default

    Quote Originally Posted by darkd0r View Post
    Any idea about price?
    Will it work with a cable speedometer?
    I don't know about price or the cable speedometer but I'll find out as soon as I can squirrel the money away to be able to buy it.
    Pete Slaney

    1979 Mustang Cobra

    347/T-5/4.30's
    420 rwhp/380 rwt (New Motor)
    11.49 @ 121.86

    306/T-5/4.30's (Old Motor)
    307 rwhp/278 rwt
    12.38 @ 111.38

  10. #10

    Default

    In 15 years and probably close to half a million miles I've never hurt a 7.5. That includes when I was 16 doing 50 miles an hour and spun out on a turn and went over a curb and hit a fire hydrant. The Locking 7.5 is weak. Put an open diff in it and you wouldn't be able to hurt it.

    As far as T fives go, I had a 3500 pound car that I put close to a hundred thousand miles on a T5 I got off Craigslist for $125. It was for a 99 to 04 V6 Mustang. I put six set of motor mounts in that car until it broke all the bolts off, messed up the motor mount holes, or just ripped everything that went to it. I was running a 275 60 on the rear and it would either deadhook at 25 miles an hour if I dump the clutch, or it would spin the tires until until 60.
    2 1986 cougars (both 4 eyed and 5.0)
    1 1987 cougar

  11. #11
    FEP Supporter
    qikgts's Avatar
    Join Date
    Jan 2010
    Location
    Rockledge, FL
    Posts
    1,458

    Default

    Great feedback everyone! Thanks for the info, all!

    Adding on to my original post, currently the 7.5 has the cone clutch "Auburn" style traction loc in it that doesn't hold the greatest, but I've also got a set of used 3.73's attached to a traditional style traction loc which perhaps I could use. Maybe I'll rebuild it with new clutches/steels and try to add an additional clutch or steel or whatever combination similar to how many folks rebuild the 8.8 posi carriers. Don't know if it would help or it make it break faster... If it's a "mass" thing that makes em' weak then maybe it would hurt... Just kickin' rocks around...
    '85 GT

  12. #12

    Default

    The Auburn is a cone clutch style and I don't think they made them for 7.5 in forever and they aren't repairable, in my experience, anyway. The factory Trak Lok clutch style I used one out of an 85 GT to upgrade my old 1979 that came with a 2.43 open diff.

  13. #13

    Default

    In 1997 I had my fill of 7.5 woes. 83 Capri, with a modified 2.3 Turbo (probably 275hp at the time if I was lucky) and an 86 SVO T5 - my 3.45 7.5 posi rear was the weak link. I broke it - then fixed and upgraded to 3.73 only to break it again 10 months later. I then upgraded to an 8.8 with 3.73's and have never looked back.

    My brother has an 86 SVO 2.3 Turbo that was stock - stock T5 and in 1999 also broke his 7.5 with 3.73 gears. He also upgraded to an 8.8 at that time.

    In both these cases these were with street tires - nothing super grippy. IMO the 7.5 is much weaker then the T5 or the 10 inch clutch.

    In some ways I wouldn't even worry about breaking the 7.5. 8.8's are still plentiful, cheap and easy to swap IMO when that day comes.
    Last edited by foot2floor; 07-19-2020 at 07:32 PM.

  14. #14

    Default

    I beat the tar out of my 84 5.0 from 86-96. Minor mods, open pipes. Drove it like I stole it. Went from coast to coast 5x. The nonWC t-5 help up like a champ. Parked that car with 220,000 mls on it. But I did replace 3 7.5's along the way. Upgrade to the 8.8 you should be golden.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •