Looking for a source for a .73 5th gearset
Thread Starter
Joined: Jan 2003
Posts: 1,613
Likes: 10
From: Tulsa, OK
Car: 1989 Formula WS6
Engine: L03 305 TBI
Transmission: T-5
Axle/Gears: 10 Bolt; 3.42 Posi
Looking for a source for a .73 5th gearset
So, I have an LO3 WC T5 with the .63 5th gear. I understand the only difference between it and the LB9 WC T5 is the LB9 T5's .73 5th gear.
Is that correct?
If so, can you upgrade to the .73 5th gear simply by swapping them out?
If so, does anyone know of a source for the .73 5th gear?
Thanks
Is that correct?
If so, can you upgrade to the .73 5th gear simply by swapping them out?
If so, does anyone know of a source for the .73 5th gear?
Thanks
Last edited by seanof30306; Jun 28, 2017 at 09:35 PM.
Joined: Dec 2001
Posts: 9,937
Likes: 636
From: Chicagoland
Car: 1989 IROC-Z. Original owner
Engine: LB9. Dual Cats. Big Cam
Transmission: World Class T-5
Axle/Gears: BW 3.45
Re: Upgrade From .63 5th Gear To .73 5th Gear?
I'm not sure it's really worth the trouble.
Supreme Member




Joined: Oct 2004
Posts: 4,528
Likes: 240
From: Henrietta NY
Car: 1984 Trans Am L69
Engine: Sniper EFI Powered 355
Transmission: WC T5 w/ Steel Support Plate
Axle/Gears: 3.42 10 Bolt Posi
Re: Upgrade From .63 5th Gear To .73 5th Gear?
My 84 TA with a L69 and T5 had the .73 I changed to a .63 when I got my new trans. I could have kept the .73 but I gained about 10mph at the same RPM with the new .63 I like it better because I use the expressway every day.
With 3.73 and .73 I was in 5th by 40 when cruising.
With 3.73 and .73 I was in 5th by 40 when cruising.
Thread Starter
Joined: Jan 2003
Posts: 1,613
Likes: 10
From: Tulsa, OK
Car: 1989 Formula WS6
Engine: L03 305 TBI
Transmission: T-5
Axle/Gears: 10 Bolt; 3.42 Posi
Re: Upgrade From .63 5th Gear To .73 5th Gear?
My 84 TA with a L69 and T5 had the .73 I changed to a .63 when I got my new trans. I could have kept the .73 but I gained about 10mph at the same RPM with the new .63 I like it better because I use the expressway every day.
With 3.73 and .73 I was in 5th by 40 when cruising.
With 3.73 and .73 I was in 5th by 40 when cruising.
Mt Firebird has 3.42 gears. I think they're the perfect gear for what I do with the car, with one exception. I don't have cruise control, and when I'm cruising on the highway, my ear always finds that 2400 rpm mark I'm used to in my Jeep. The problem is, that's 80+ mph in my Firebird. The highway I take to work every day has a 60 mph speed limit in town, and 65 mph out of town. They enforce it. In the past 10 years, I've gotten 3 tickets in the Firebird for that.
I've got to have the transmission rebuilt (again). I figure as long as I've got to do that, I might as well get the 5th gear I want while I'm doing it.
I know there's no source for new ones. I saw something on the internets from a guy who rebuilds Mustang T5s saying he could give a 2.95 first gear transmission an overdrive of .63. .73. or .83, depending on the gearset combination he used. Haven't been able to get ahold of him to learn more. Does that make sense?
What are the tooth counts on the .73 5th gearset?
Last edited by seanof30306; Jun 28, 2017 at 09:36 PM.
Supreme Member

Joined: Jul 1999
Posts: 2,755
Likes: 10
From: Ahead of you...
Car: 1984 LG4 Camaro
Engine: 350 Roller Motor
Transmission: Level 10 700R4
Axle/Gears: Strange 12 bolt 3.42
Re: Upgrade From .63 5th Gear To .73 5th Gear?
I thought the non WC T5 had a 2.95 1st gear, where the WC T5 had the 2.75 1st gear?
Thread Starter
Joined: Jan 2003
Posts: 1,613
Likes: 10
From: Tulsa, OK
Car: 1989 Formula WS6
Engine: L03 305 TBI
Transmission: T-5
Axle/Gears: 10 Bolt; 3.42 Posi
Joined: Jul 2000
Posts: 6,522
Likes: 92
From: Aridzona
Car: `86 SS / `87 SS
Engine: L69 w/ TPI on top / 305 4bbl
Transmission: `95 T56 \ `88 200-4R
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Thread Starter
Joined: Jan 2003
Posts: 1,613
Likes: 10
From: Tulsa, OK
Car: 1989 Formula WS6
Engine: L03 305 TBI
Transmission: T-5
Axle/Gears: 10 Bolt; 3.42 Posi
Re: Upgrade From .63 5th Gear To .73 5th Gear?
"Can 5th gear be geared down or up from stock overdrive?
Yes, 5th gear can be changed from .68 to .73, .80, or 90. .63 can be changed to .59, .73, or .83"
http://www.moderndriveline.com/md_fa...shtml#02136553
Yes, 5th gear can be changed from .68 to .73, .80, or 90. .63 can be changed to .59, .73, or .83"
http://www.moderndriveline.com/md_fa...shtml#02136553
Thread Starter
Joined: Jan 2003
Posts: 1,613
Likes: 10
From: Tulsa, OK
Car: 1989 Formula WS6
Engine: L03 305 TBI
Transmission: T-5
Axle/Gears: 10 Bolt; 3.42 Posi
Re: Upgrade From .63 5th Gear To .73 5th Gear?
I just had a conversation with Paul at Modern Driveline. Very nice guy. A lot of what he said was over my head, so be patient with me.
He said the .73 5th gearsets are no longer available. He's getting ready to have them produced for 28 spline mainshafts, and it wouldn't be a problem to have them go ahead and make them for the 27 spline mainshafts, too. He's at least 3 months from having those parts though, so no bueno for me.
He said he could give me a .8 5th gear by swapping to a Ford mainshaft. He said he'd also have to swap some parts to get my speedo to work. All new parts, about 550. Gotta think on that one. I really like the idea of the .8 OD and all new parts, but that's a little steep. Here's the .8 gearset:
http://www.moderndriveline.com/Techn.../80gearset.htm
The simplest solution would be to just find a good, used 55 tooth / 31 tooth 5th gear set. That's the LB9 5th gear set. I looked on ebay and in the classifieds here. No luck so far.
Last edited by seanof30306; Jun 28, 2017 at 09:45 PM.
Thread Starter
Joined: Jan 2003
Posts: 1,613
Likes: 10
From: Tulsa, OK
Car: 1989 Formula WS6
Engine: L03 305 TBI
Transmission: T-5
Axle/Gears: 10 Bolt; 3.42 Posi
Re: Looking for a source for a .73 5th gearset
Also, the V6 GM T5s had a 53 tooth / 23 tooth 5th gearset for a .76 OD. Will these fit my T5? If so, it's an easy fix, they're everywhere.
EDIT. OK, scratch that. V6 gearset es no bueno
EDIT. OK, scratch that. V6 gearset es no bueno
Last edited by seanof30306; Jun 30, 2017 at 12:25 AM.
Re: Looking for a source for a .73 5th gearset
[QUOTE=seanof30306;6148715]So, I have an LO3 WC T5 with the .63 5th gear. I understand the only difference
What gears are in my t5 non world class its in a 88 camaro w a 350 posi track rearend and 5th gear is out what is the name or part number i need please anyone
What gears are in my t5 non world class its in a 88 camaro w a 350 posi track rearend and 5th gear is out what is the name or part number i need please anyone



