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Thread: Correct battery size and fitment of Mustang battery trays

  1. #1
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    Default Correct battery size and fitment of Mustang battery trays

    I believe our correctly sized battery is group 65, correct? The 87-93 mustangs call for a group 58, correct? Do the Mustang trays swap in without modification into our cars? Mine is cracked, and I want something in mint condition moving forward.

    I'm curious because my Optima is now useless after 7 years so a new battery is needed. I'm looking at Sears' DieHard Platinum series (same as Odyssey) as a replacement AGM, since the things never corrode posts or vent gases (had fun with a Costco battery years ago - left a mess in the area). They appear to offer size 34/78 and 65. My current 34/78 Optima has always been loose in the tray, and I want something with a better fit, but if I get a "new" tray from Mustang parts, I think the group 65 one won't work.
    Last edited by Seek; 02-12-2014 at 12:22 AM.

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    I have a sn-95 tray in my tbird. bolted and looks identical. not sure the year.
    Quote Originally Posted by jcassity
    I honestly dont think you could exceed the cost of a new car buy installing new *stock* parts everywhere in your coug our tbird. Its just plain impossible. You could revamp the entire drivetrain/engine/suspenstion and still come out ahead.
    Hooligans!
    1988 Crown Vic wagon. 120K California car. Wifes grocery getter. (junked)
    1987 Ford Thunderbird LX. 5.0. s.o., sn-95 t-5 and an f-150 clutch. Driven daily and going strong.
    1986 cougar.
    lilsammywasapunkrocker@yahoo.com

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    I've got a Fox Mustang replacement battery tray from late model restoration in my Thunderbird. It was identical to the stock battery tray and fits a stock replacement Thunderbird battery just like the stock battery tray.
    '88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, Edelbrock 70mm TB, 76mm C&L MAF, 30lb injectors, 2.5" exhaust, AOD with 2800 PI converter, 8.8 with 3.73 gears, 31 spline Traction-Lok, 31 spline Moser axles, 04 Cobra front arms, Maximum Motorsports extreme duty rear arms, subframes.
    '11 Focus, '12 Mustang 3.7, '17 Accord EX-L V6

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    Sounds good. I found people who say that size 65 fits in their fox Mustangs, so I'll stick with that battery and a new tray. I can't even start the car now. 12.6V off the Battery Tender, 11.4V after a couple seconds of cranking. The Optima battery is not happy.

    Thanks guys!

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    seems like the battery makers are migrating away from group numbers.. im seeing new numerology on these lately and i have to learn it all over again.

    the UPS batteries i often deal with have a direct connection with group number to AH rate , typically the C/5 where capacity divided by 5hrs... these numbers im seeing are not making sense.. speaking to advance auto specifically.

    group 65 in the GNB or Unigy or C&D world would tell mebi could discharge to 1.85vpc at the C/5 should allow me to use 13amps for one full hour.

    auto batteries dont "list" thier specs like i think they should ,, they list some but most importantly is watts per cell which is a tell all sign of the plate design which is getting cheaper by the year.

    one typical 12v battery i see all the time is the 12avr170FT ~aka 12v front terminal 170ah battery,, at the C/5 rate it can provide about 34a for an hour.

    wow did i get off topic
    Last edited by jcassity; 02-12-2014 at 02:59 AM.

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    FYI this is what I bought several years ago: http://www.latemodelrestoration.com/...L-Battery-Tray
    Identical in every way to the stock Thunderbird piece.
    '88 Thunderbird LX: 306, Edelbrock Performer heads, Comp 266HR cam, Edelbrock Performer RPM intake, Edelbrock 70mm TB, 76mm C&L MAF, 30lb injectors, 2.5" exhaust, AOD with 2800 PI converter, 8.8 with 3.73 gears, 31 spline Traction-Lok, 31 spline Moser axles, 04 Cobra front arms, Maximum Motorsports extreme duty rear arms, subframes.
    '11 Focus, '12 Mustang 3.7, '17 Accord EX-L V6

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    Quote Originally Posted by thunderjet302 View Post
    FYI this is what I bought several years ago: http://www.latemodelrestoration.com/...L-Battery-Tray
    Identical in every way to the stock Thunderbird piece.
    I don't get what the difference is from http://www.latemodelrestoration.com/...ttery-Tray-Kit ? Just a Ford part vs reproduction?

    I got the new DieHard Platinum 65 in there last night, I need a post sleeve for the negative battery post, but even with just slight terminal contact, it fires up very quickly using my mini starter on a ~9.8:1 static compression motor. New batteries are always great, but especially one rated 200CA higher than my old tired Optima.

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    Quote Originally Posted by Seek View Post
    12.6V off the Battery Tender, 11.4V after a couple seconds of cranking.
    11,4V while cranking is an excelent result. Normal numbers are around 10 V.
    '85 Thunderbird TC '86 Thunderbird TC '97 Scorpio 2.3 GHIA

    T-Bird / Cougar DIY stuff

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    That was after cranking, not during. the battery must have lost a ton of capacity to get that low in only a few seconds.
    Quote Originally Posted by jcassity
    I honestly dont think you could exceed the cost of a new car buy installing new *stock* parts everywhere in your coug our tbird. Its just plain impossible. You could revamp the entire drivetrain/engine/suspenstion and still come out ahead.
    Hooligans!
    1988 Crown Vic wagon. 120K California car. Wifes grocery getter. (junked)
    1987 Ford Thunderbird LX. 5.0. s.o., sn-95 t-5 and an f-150 clutch. Driven daily and going strong.
    1986 cougar.
    lilsammywasapunkrocker@yahoo.com

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    Yeah - I don't know what it was dropping to while cranking. The starter would barely turn for a couple seconds, then nothing. 50A charger on the car would get it to barely start if the battery started out "full". Not a problem now with the new battery. Runs great after I fixed a dumb vacuum line misconfiguration.

    Last time I started the car was probably in the fall, and it started up just fine. It has had dozens of of complete drains in its life time, so it was time to put the battery down. The most annoying part is that I think I left a brass post sleeve/shim on the battery when I left it at Sears while picking up the replacement battery. I need to pick up another shim to get my negative terminal installed correctly.

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