I want to change the fluid in my tranny
it looks like it has gear oil in it now,but
the dealership told me 82-86 F-body's with
T-5 take ATF, a differnt dealer said
syncro mesh fluid. What should I do
if i go with ATF i think ther may be
some gear oil left and i dont know if
they can mix. Please help..

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86 T/A L98 with T-5(orig an LG4)
Hooker headers
Performer RPM intake
holley 750cfm carb
cast iron 76cc heads with
2.02-1.60 valves
B&M ripper
Richmond 4.10's
Flowmaster
9.43@74mph 1/8 mile.

 

Rule of thumb is that if it's the 1st design, use light gear lube (80W-90 or 75W-90), and if it's the "World Class", use ATF. Although the world won't come to an end if you use either one in either trans. Your 86 is the non-WC ealry design, so it should be gear lube.

The various factories that have used T-5s in their cars over the years, including GM, have been about equally conused. GM recommended ATF in these cars in one year when they were still using the 1st design gearbox, then they switched back. Nothing inside the trans changed in the slightest. Ignore all that.

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"So many Mustangs, so little time..."
ICON Motorsports

 

we took a wc t5 out of my sons car that had gear lube in it and sold it to someone and he's ran it for 2 years with atf in it with no problems.

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ICON Motorsports
1st & 3rd
MM Black Diamond 538 F&AM

 

When should you change your trans fluid. For a T-5 I mean. Mine is 11 years old and not many miles on it. Is the lube still good or all broken down from age?

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1990 RS 305 TBI T-5
.5" turbocity spacer
Summit 14X3 OpenElement W/k&N
Hooker 3" Areochamber
MSD - Wires, Cap, Rotor, Coil
Bosch Platinum +4 plugs
Metallic Red w/28,000 Pampered miles
(Still have the original wiper blades)

 

Thats news to me, I'm told if you use gear oil in a world class T5 you'll burn up the synchros. T5's should use ATF.

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1991 Camaro Z28
5.7L 5-Speed (originally 305)
13.23 @ 107.62 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Webmaster: SoCal F-Bodies
-=ICON Motorsports=-

 

I use ATF in my T-5.

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85 2.8L Sport Coupe 5-speed.
Mods: Hpertech chip and powerstat, MSD 6A-L, Crane fireball coil, Accel Cap and Rotor, Dynomax hi-flow cat and catback system with a dynomax magnum race bullet muffler on the i-pipe, K&N filterchargers, Gutted Air Boxes, 8mm Wires, Eibach Sportlines and Tokiko springs/shocks setup, Global west sub frames, Suspension techniqs front and rear sway bars, and good ole 88 IROC wheels with Kumo Ecstas on em!
"It's not the ricers, it's those damn V8's!"

Wins: 2000 V6 Accord, 69 302 Mustang, 2000 Auto VR6 Jetta, 89 Toyota MR2, 90 Civic Si, 76 350 Camaro.

 

ATF in my T5 in my 85 IROC.

JamesC

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[This message has been edited by JamesC (edited August 04, 2001).]

 

My 91 (WC) T-5 has had half and half Mobil 1 ATF and Mobil 1 gear lube in it for 35k miles or so... Matt98SS ran Red line MTL in it for some time before that... I don't think the synchros are being hurt, but maybe it's too soon to tell

As has been said, having good clean fluid is more important than exactly what kind of fluid it is

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"So many Mustangs, so little time..."
ICON Motorsports

 

When I bought an '83 Z28 in 1986 I found this watery red stuff in the tranny and I just about freaked. Some moron had put ATF in a manual transmission! The 1983 Helm manual said to use gear oil and that's what I put in there. Only later did I learn that B-W/GM switched to ATF at some point. The 1985 Camaro Helm manual specifies Dexron II for both the automatic and T-5. I've also been told by a guy that works at a transmission shop that they put synthetic engine oil in T-5s to make them live longer. My own opinion is that the switch was made to ATF at about the same time the manufacturers went to 5W30 for engine oil in an effort to marginally improve overall fleet gas milage to please the feds. I'd say if it worked fine with gear oil, keep using it. Try ATF if you want; you can always change back if you don't like the way it shifts. It makes good flushing oil.

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1985 Yellow IROC-Z 5.0 HO, T-5 3.73 Torsen, 4 wheel disks
PFCM pads, GTA wheels, Koni yellows, B&M Ripper, Dynomax

 

I believe that 83-86 used gear lube, 87 used 5W30 oil, and 88 and newer use ATF. This is according to Hayne's and Chilton's.