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Help figuring out speedo gear that I have and I need.

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Old 06-14-2012, 01:36 PM
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Car: 86 Trans Am/85 K5 Jimmy
Engine: 406 FIRST/350 TPI
Transmission: TKO 600/700R4
Axle/Gears: 9Bolt/10Bolt front & back
Help figuring out speedo gear that I have and I need.

I just got up under my car and turned a tire one full rotation to count the driveshaft rotations. It turned right about 3 1/4 turns so it looks like I have 3.27 gears in my 9 bolt. Ive got a T5 transmission in the car. (1986 TA) It was originally a LG4 Auto car I believe. Bought it without a engine but came with the T5.
Anyways, my speedometer is off. It reads 60 when Im going 75. How do I go about figuring out what drive/driven gear I need for the VSS? I have no idea what gears are in it currently, I will try to get under there and figure it out tomorrow.

Last edited by dabomb6608; 06-15-2012 at 01:27 PM.
Old 06-15-2012, 01:28 PM
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Car: 86 Trans Am/85 K5 Jimmy
Engine: 406 FIRST/350 TPI
Transmission: TKO 600/700R4
Axle/Gears: 9Bolt/10Bolt front & back
Re: Help figuring out speedo gear that I have and I need.

Anyone? I need to get this fixed so I can continue on with my tuning.
Old 06-15-2012, 02:39 PM
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Car: 1989-92 FORMULA350 305 92 Hawkclone
Engine: 4++,350 & 305 CIs
Transmission: 700R4 4800 vig 18th700R4 t56 ZF6 T5
Axle/Gears: 3.70 9"ford alum chunk,dana44,9bolt
Re: Help figuring out speedo gear that I have and I need.

your best bet is to pop the cover of it and check the gear ratio, then look in the service manual or parts books for the correct drive and driven gear tooth count for your rear gears.

Last edited by TTOP350; 06-15-2012 at 04:30 PM.
Old 06-15-2012, 02:50 PM
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Car: 86 Trans Am/85 K5 Jimmy
Engine: 406 FIRST/350 TPI
Transmission: TKO 600/700R4
Axle/Gears: 9Bolt/10Bolt front & back
Re: Help figuring out speedo gear that I have and I need.

Well going by the old turn tire 1 revolution and count driveshaft rotation I got 3 1/4 turns. The 9bolts from what I have read did commonly come with 3.27 gears so I believe that method to be fairly accurate. I could take the cover off and check to be sure, but I'm not ready to jump out've my chair to go do that if you get what I mean. I'd rather not be under the car anymore then I have to.
Old 06-15-2012, 04:34 PM
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Car: 1989-92 FORMULA350 305 92 Hawkclone
Engine: 4++,350 & 305 CIs
Transmission: 700R4 4800 vig 18th700R4 t56 ZF6 T5
Axle/Gears: 3.70 9"ford alum chunk,dana44,9bolt
Re: Help figuring out speedo gear that I have and I need.

Then call/go to dealer,(or use google till ya find it) and tell em you have 3.27 gears in your 86 TA and see what drive and driven gears you need to get.

Buuuut if you 4 sure have 3.27s, I would try 7 tooth drive and 19 tooth driven ;-)

Last edited by TTOP350; 06-15-2012 at 05:12 PM.
Old 06-16-2012, 02:49 PM
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Car: 86 Trans Am/85 K5 Jimmy
Engine: 406 FIRST/350 TPI
Transmission: TKO 600/700R4
Axle/Gears: 9Bolt/10Bolt front & back
Re: Help figuring out speedo gear that I have and I need.

Ok, I will try and check which drive/driven gears are in it now sometime and then go from there. Thanks for the help TTop
Old 06-17-2012, 08:45 AM
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Re: Help figuring out speedo gear that I have and I need.

7 tooth drive gear, 18 tooth driven gear.
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