Which Transmission for my 1966 C10 with 496 BBC

[Nils]

Hello,
I have a 66 C10 long bed with the original 283 sbc and the
3 on the tree manual transmission. Now i would put a 496 Stroker
Bbc with a automatic transmission in it. My Axle Gear Ratio is the original 3.73:1.
I am a cruser and not a racer. I would like to have low rpm on the highway.
I think about to put a TH400 in it. A 4L80E had an Overdrive, but i dont want to put much electric in the Truck. A Gear Vendor Overdrive is to expensive a think.
Maybe change a 3.08:1 Rear ?
Is there a other option?

Thank you all verry much.

Greetings from Germany.

Nils

[geezer#99]

What’s the specs on your 496?
Not all motors like to do low rpm cruising.
With a 28 inch tall tire you’d be turning 2900 rpm with 3.73’s, 2400 rpm with 3.08’s at highway speed of 65 mph.

Use this calculator for speed/rpm/tire size changes.

http://www.advanced-ev.com/Calculators/TireSize/

[Nils]

Originally Posted by geezer#99

What’s the specs on your 496?
Not all motors like to do low rpm cruising.
With a 28 inch tall tire you’d be turning 2900 rpm with 3.73’s, 2400 rpm with 3.08’s at highway speed of 65 mph.

Use this calculator for speed/rpm/tire size changes.

http://www.advanced-ev.com/Calculators/TireSize/

Hello,
It is a 4 Bolt Block with cast iron large oval port heads and a
Edelbrock # 7561 RPM Air-Gap 2-O intake. It is a mild tuned Engine. Maybe
400-500 HP.
I think a TH 400 with a long tailshaft is god to use a shorter one piece
Driveshaft.

[Captainfab]

I would go with the 4L80E if you want to keep the 3.73 gears. The controller is about $600. If you go with the TH400 I would change the gears to 3.08 if you plan on doing much highway/freeway driving. the 3.42 gears is a happy medium. That is what I have in my '66 Suburban with a mild built 461/TH400. The RPM's are still a little higher than I like but I have driven it over 100,000 miles that way

[AcampoDave]

Yep, I gree with the turbo 400 and 3.08 combo. I like keeping it simple. A big ol' motor like that should spin a 3.08 with ease.

[Nils]

Originally Posted by AcampoDave

Yep, I gree with the turbo 400 and 3.08 combo. I like keeping it simple. A big ol' motor like that should spin a 3.08 with ease.

Thank you all verry much for your help.
I have found a TH400 with long tail. The Owner say it comes out of a C20
Long Bed. I think it could fit.

[Nils]

I have read something about the TH375 and hope this Transmission is not the light Version
Of the TH400. What are you thinking?

[cwcarpenter98]

The casting numbers on your transmission should tell you what you have

[Nils]

Originally Posted by cwcarpenter98

The casting numbers on your transmission should tell you what you have

Hi, the problem is that a only have this two Pictures. I pick it up in 2 Weeks far away from my home. I thought
It is a 400 because of the oil pan shape. I think under the tailshaft there are the 375 Numbers.

[geezer#99]

If it’s a 375 it’ll be marked on the tailshaft.
Wiki here.

https://en.wikipedia.org/wiki/Turbo-Hydramatic

[urmyboyblue]

I have run a TH375 behind my 550 HP bbc, nothing wrong with them. It is a TH400 with a TH350 output shaft. Will be fine for your application.
Posted via Mobile Device

[Nils]

Originally Posted by urmyboyblue

I have run a TH375 behind my 550 HP bbc, nothing wrong with them. It is a TH400 with a TH350 output shaft. Will be fine for your application.
Posted via Mobile Device

Hi, i read that some intenal parts are not so strong like the 400.
If only the output shaft is longer it will be fine for me. But a dont want
A bad transmission. What was the reason of build a 375 ? Only the output shaft?

[urmyboyblue]

I am not sure why GM made them- perhaps to commonize drive shafts with the TH350. Like I said, with my experience with it behind my big block, I will run one any day. Your engine shouldn't be too much for a TH375. It has been a while since I read up on the differences- if I remember correctly, the only internal difference was the use of one less clutch plate in one gear.

[Nils]

Did anybody know what means the number 26 of the Transmission?

[ol_skool_chevy]

I have a 496 BB in my truck and I use a all new turbo 400 with a Gearvendors overdrive 3:42 gears.