# 2nd gne diesel 9 speed transmissi9n fluid



## mr overkill (Dec 1, 2013)

Would. The wrong transmission fluid cause the car mpg to drop??


Dealer installed a gm trans amd has since had a 1-2 2-3 "flare" but also I am trying to trace a big mpg loss. I wonder if fluid type could be wrong causing "transmission drag"


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## Snipesy (Dec 7, 2015)

No not really.


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## 6speedTi (May 18, 2018)

Hopefully the same exact part number transmission was replaced. I did some reserach on a similar issue but with a manual transmission. Same transmission model number but with various gear ratios from 1st to 6th. 
Same model transmissions with various part numbers for different model vehicles and worldwide markets. 
Something to consider.


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## Barry Allen (Apr 18, 2018)

6speedTi said:


> Hopefully the same exact part number transmission was replaced. I did some reserach on a similar issue but with a manual transmission. Same transmission model number but with various gear ratios from 1st to 6th.
> Same model transmissions with various part numbers for different model vehicles and worldwide markets.
> Something to consider.


That's a legitimate concern.

I remember reading an article a while ago when the 2nd Gen Cruze Diesel was launching, and GM picked a low final drive ratio to achieve the 54 mpg highway fuel economy rating. Don't know about the individual gear ratios, but maybe those were the same as the gasoline engine.

Either way, the transmission in a vehicle should match the OEM gear ratios and then the same final drive ratio for what the vehicle was built with. This should apply unless you are doing a custom build with different gear ratios in the transmission.


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