Moparts Tech Archive

Automatic Trans.

Speedo Gear Change

Will I need to drain the trans in order to change the speedo gear ?
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Quick Kurt
Moparts Member
Posts: 1261
From: Pittsburgh, Pa, USA
Registered: Jan 2002

No, you'll only lose a little bit of fluid. Jack it as high as reasonably possible in the rear, and have a catch pan ready, just in case.
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70Duster
Moparts Member
Posts: 446
From: Hershey PA
Registered: Nov 1999

Don't bother to drain the trans. Just jack the rear of the car up as high as you can, support it with jack stands and pull the speedo gear adapter out. You will lose very little or no fluid this way
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Don1
Moparts Member
Posts: 3248
From: Valley City, ND. USA
Registered: Oct 2001

Make sure that you index the new gear proerly or it either won't read or will chew up the plastic gear. Depending on if you have it in too close or too far off the shaft drive.
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romanucci
Moparts Member
Posts: 323
From: Butler, PA USA
Registered: Jul 2000

What do you mean by "Index the new gear"??
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71ChargerSE440CI
Moparts Member
Posts: 2540
From: Rancho Cucamonga, So. California, USA
Registered: May 2001

All great replies so far. The housing has an O-Ring seal. Some fluid will leak out, but not much if you raise the rear of the car.
As for "Indexing" the gear housing, there are markings cast into the gear carrier and an arrowhead cast into the case opening.

Depending on the number of teeth, there is a range setting and the index marks corresponding to the number of teeth must be lined-up with the arrowhead.

Also, I noticed that sometimes the gear-carrier/adapters can be different.
I have four 727 TF's. Two have one type/set of gear tooth ranges, and the other two are more limited, so they CAN be a bit different.

I once had to salvage a different adapter off another trans to allow the gear-tooth count gear I intended to use.

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crankshaftkid
Moparts Member
Posts: 4295
From: Stinkerdener (Pasadena) TX
Registered: Feb 2000

Once you get to that area, you'll see the adaptor is marked for the different gear teeth. It's pretty easy to see it if it's clean. Index accordingly
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John Kunkel
Moparts Member
Posts: 2251
From: Rio Linda, CA, USA
Registered: Nov 1999

The most common speedo pinion adapter with the various positions highlighted.

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You rotate the pinion adapter until the tooth range you're using is at the 6 o'clock position, as shown in the attached image.

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