Final Drive

gunloader55

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Aug 8, 2023
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Does anyone run a 3.42 Cinnabar drive, and what kind of performance are you getting with the 455?

I’ll be towing small truck or trailer occasionally, would like to run around 65mph on flats.
 
Certainly better than the factory 3.07. You might also consider the 3.55 option from Applied GMC. It's available in a limited slip version. For more mountainous terrain, the 3.70 is a good option.
 
If you are towing you should be running the 3.70.
I run 60mph all day long at 2800 to 3000 rpm
Why would you spend that much money and only get a 3.42?
Most people are just scared.
 
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If you are towing you should be running the 3.70.
I run 60mph all day long at 2800 to 3000 rpm
Why would you spend that much money and only get a 3.42?
Most people are just scared.
A 3.4 is in motorhome I’m looking at. I’m wondering if I’ll get decent performance out of it for my needs.
 
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I just installed a 3.42 last fall. I got it from a fellow who had a '78 23ft with a 403 and had changed to a 3.70.

I have a '77 with a 455 and it made a big difference in acceleration and hill climbing. It took a bit to get used to the higher engine RPM's. GM designed the 3.42 knowing that the 3.07 was too tall, but they never got it into production. When Cinnabar purchased the rights to make replacement parts from GM, they got the drawings for the 3.42 design.
 
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where the 3.70's really shine is driving on secondary windy hilly roads where you rarely exceed 55.
with the 3.07 the 455 struggles and downshifts on the little hills.
With the 3.70's the 455 is much happier and doesn't need to downshift

Jim B says:
 
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I don't know if this made it through the last post, So I will post it again and hope that it doesn't come up as a duplicate.

The 3.42 final drive puts the peak performance and efficiency of the 455 engine (2,800 RPM) at 65 miles an hour. Basically meaning that at 65 miles per hour you are operating you engine at its best and healthiest condition.

Minus the toad or forever driving up hills, it is the perfect differential for our coaches. IMHO.

Everyone have a wonderful evening,

Tom K.
 
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The 3.42 was and still is very sought after, but I believe it is no longer in production, so many went to the 3.55 etc. With the stock motor and stock transmission the 3.42 puts your engine exactly where it needs to be at 65 MPH.

You will not have a problem selling that 3.42.

Take care,
Tom K.
 
The 3.42 was and still is very sought after, but I believe it is no longer in production, so many went to the 3.55 etc. With the stock motor and stock transmission the 3.42 puts your engine exactly where it needs to be at 65 MPH.

You will not have a problem selling that 3.42.

Take care,
Tom K.
This is news to me. I know people who have bought the 3.42 in the past year.
 
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That's why I said "I believe" and not "I know". It's great news if there's still being kicked out at cinebar or any where else. Was there a cease in production or supply some time ago?

Take care,
Tom K.
 
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I remember Wes Cauphlan of Cinnabar did not like the 3:70 and pushed the 3:42.
That isn’t necessarily fatal to the 3.70. Cinnabar is a business and the 3.42 is the factory design that they sold. Caughlan has always considered himself a provider of “factory” parts, even if he has to have them made by suppliers. He has always favored the use of the original designs over the newer designs. The 3.42 was not an original design but it was a factory design that never made it into production before GM discontinued the drivetrain.

Rick “uses a 3.21 but doesn’t tow and has a light coach” Denney
 
I'm not sure any of them are being made anymore, probably just selling off old stock.
I'm thinking Cinnabar would have committed to a minimum run order from the manufacturer. When their inventory runs low, they will have to consider the risks of having another production run made vs the potential sales.
So indeed they are not made anymore and they are selling existing stock... Until they have more made.