five7kid

iTrader: (14)

The '66 TH400 now in my '57. I had 3.73 gears put in from the 3.08's, picked a drive and driven gear to match the new ratio. When I pulled the tailshaft housing to install them, I found what looked to be a machined-in drive gear - not replaceable.

Either I don't know what I'm looking at, or there is a very interesting way that gear is being held on the tailshaft.

Anybody run in to this before? Did they change the speedo drive design in later years? The drive gear I picked up fit the yoke splines, but the splines ended before getting to the existing gear.

five7kid

iTrader: (14)

I was hoping one of you old farts would have an idea about the TH400 configurations. It looks like I'm going to have to find an outside gear reducer, because the driven gears don't come large enough to do the trick for this combo.

Vader

5-7,

IIRC, the 400s and 350s were like the Powerglides in that the steel drive gear (ring) was pressed/shruken onto the tailshaft.

Sorry I didn't see this earlier, but I don't get on the Trans/Axle board very often.

Vader

OOPS! Wrong! That was a 350. Let's try again...

five7kid

iTrader: (14)

TH350s, from what I remember on the '77 Monte I had, was held on by a little clip between the gear & shaft. The drive gear sold to me by the tranny shop was supposed to be held by a c-clip, I thought. Your illustration looks like mine, though. Is that supposed to cover any particular year(s)?

Oh, well, I'm not going to be replacing a pressed-on gear anytime soon.

(I figured the "old fart" reference would wake somebody up. Works on me...)

Nordbert

I checked the speedo drive gear on my TH400 CJ-68-9133. It
was steel and pressed on almost next to the governor drive
gear which is machined into the shaft. You might be able to
order speedometer gears for something like a '67 Chevelle
SS 396 w/3.73's if they aren't obsolete.

five7kid

iTrader: (14)

I was in a hurry, to say nothing about disappointed that my gears wouldn't work, so I didn't even count the teeth on the drive gear. But, the driven was 42, and best info I've gotten indicates 45 is the biggest they make.

But, I'll check to see if the gear you suggested is available.

88 427 Camaro

I have a book on T400's by Ron Sessions that is excellent. Unfortunately, I won't be able to check it until the end of the month, but the ISBN# and stuff is listed on my page at www.koolmeister.com

Miles

five7kid

iTrader: (14)

I've got the book. Didn't even think to look there. I've pretty much read all through it, but don't recall anything specifically on the speedo gearing. I'll have to look again.

88 427 Camaro

Five7kid,

This old fart was able to make it home for the evening before heading out tomorrow morning (atleast it is to somewhere warm this time, ie Orlando & Fort Myers).

Check page 154 of the Sessions book. Looks like someone already replaced the drive gear with a steel one and hence you will have to chisel or pull it off.

Miles

five7kid

iTrader: (14)

Yes, I saw it when I got home, same page. You just beat me to the post.

The new plastic gear I bought has splines, not a press-on. I think I'll just get a reduction box made for it.

Well, now we all know...