CY & CX 400THM: differences & similarities

@wot · #1 06-27-2005, 05:20 AM

Forgot to ask if anyone has a source for speedometer drive gears for TH 400?

Thanks

**Mr70** · #2 06-27-2005, 07:09 AM

I have compiled a list of speedometer gears.
What specifically are you wanting to know?
Color-Ratio-Part#?

Look for a CON VIN possibly stamped around the bell housing as well as into a recessed machined pad located were the Trans. oil pan meetes the trans. valve body.
It's behind the shift linkage rubber boot.
It is parallel to the head pipe,so you will have to look behind the head pipe,and wipe the pad clean to notice.

@wot · #3 06-27-2005, 04:00 PM

Mr70,

Thanks for the reply. I need the stock replacement gear for a TH400 with 3:55gears. Someone had changed it when they changed the tire size.

**Mr70** · #4 06-27-2005, 04:30 PM

Gear Part #9780470,Gray in color with 44 teeth used on 3:55 ratio with F70X14,G70X14 tires on 1968 Chevelle-Elco-Camaro.

**WILMASBOYL78** · #5 07-04-2005, 05:29 AM

What are the shift points on the L78 th400 trans setup under full throttle application? If you just start out in "drive" and floor it, at what rpm will it shift fron 1-2 and then 2-3?? Trying to dial in the trans in one of my cars with th400 and 4.10 rear.

wilma

**WILMASBOYL78** · #6 07-05-2005, 05:38 AM

Any th400 experts have some feedback???

thanks, wilma

**Mr70** · #7 07-05-2005, 06:40 PM

I want to say my L-78 TH400 Chevelle fitted w/4:10/F70X14 shifts from:
1-2 @ 10-15MPH.
2-3 @ 18-25MPH.
I can double check the RPM for you this week..

I see a 70 Nova L-78 w/3:55/E70X14 shifts from:
1-2 @ 7-12 MPH.
2-3 @ 18-35 MPH.

fpcopo · #8 10-14-2005, 08:26 AM

To Wilmasboy:

My research has said that the design upshift speed at WOT of the 69 CY trans was 5900 to 6100. The high speed governor will help you up your shift points but also affecting shift timing are line pressure and accumulator springs and pistons. Also the trans was designed for hard use as all wavy shift plates from clutch packs were removed for harder as well as quicker shifts. Some other mods were the forward clutch drums have 2 oil bleed check balls instead of 1, this allows oil to dump faster to speed shift timing. The 6 lug convertors were first used in trucks so you can find trucks with the same convertor shell but everything inside is vastly different. Frank

nuch_ss396 · #9 01-04-2006, 08:54 PM

[ QUOTE ]

The 6 lug convertors were first used in trucks so you can find trucks with the same convertor shell but everything inside is vastly different. Frank

[/ QUOTE ]

Frank,

I recently found a 69 CX THM400 out of an L/78 Nova. I now
need the correct 6-lug converter. I see them on eBay from
time to time, but you comment about the truck converter
being vastly different concerns me. How does one know if
you have a true SHP 6-lug converter? Or, are they still
available from GM with the proper internals for an L/78?

BTW, were the SHP converters stamped or coded in any way?
Steve

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