WK Tranny question

[Colt45auto]

W5A580 Tranny,

This is the stock tranny in the 3.7L and the 6.1L? I though the tranny was better in the 4.7 & 5.7L (545RFE) engine groups? If the 545RFE is better, why is the W5A580 in the 6.1L package? Seems DC would want the heavier duty tranny behind the big engine.

Which is the more HD transmission?

[wkearney99]

The requirements for towing and off-road four wheeling is somewhat different that just making it go. Neither the 3.7 or the SRT8 are rated for towing all that much. That and the SRT8 uses an entirely different transfer case.

wkjeeps has an article on the transmissions.

[zwaghuf]

Counter point: The CRD uses the same tranny as the 3.7 & SRT8 and is rated to tow 7400lbs (200 more than the Hemi)

[LordGriNz]

Originally Posted by zwaghuf

Counter point: The CRD uses the same tranny as the 3.7 & SRT8 and is rated to tow 7400lbs (200 more than the Hemi)

Mainly because the 3.7 GC weighs less, not because its a better tranny...

[BrianM83]

pre op or post op tranny?

[zwaghuf]

Originally Posted by LordGriNz

Mainly because the 3.7 GC weighs less, not because its a better tranny...

What does the weight of a 3.7 WK have to do with the CRDs tow rating? I also never said it was a better transmission.

[autofetch]

Originally Posted by BrianM83

pre op or post op tranny?

haha.

Wow.

[LordGriNz]

Originally Posted by zwaghuf

What does the weight of a 3.7 WK have to do with the CRDs tow rating? I also never said it was a better transmission.

Throw ten people in the jeep and then tell me if you can tow more or less...

[Bottom16]

Maybe it has to do with the gear ratios in the transmissions. The 3.7 needs a shorter (nigher numerically) first gear to get it going due to lack of power vs. the 4.7 and 5.7 HEMI's. As for the 6.1L, maybe they want the gearing shorter for the off the line jump to compete with the Cayenne Turbos of the world.

Just my 2 cents.

[Jkram]

I read (somewhere?) the MB tranny has closer gear ratios and it meant better acceleration numbers. That is why it is in the SRT. I think the 545rfe is stronger but they are both strong enough for their tasks.

[JeepCollector]

Originally Posted by zwaghuf

Counter point: The CRD uses the same tranny as the 3.7 & SRT8 and is rated to tow 7400lbs (200 more than the Hemi)

Actually they have the same tow rating - 4x2's are 7400 and 4x4's are 7200. The Dodge Ram 1500 and Durango use the 545RFE with towing up to 8950 lbs in a heavier vehicle.

[zwaghuf]

Originally Posted by LordGriNz

Throw ten people in the jeep and then tell me if you can tow more or less...

Now... this is just a guess, but ah, I'm thinking if you put 10 Mexicans in a 5 passenger GC, its towing ability would be reduced, regardless of the transmission.

Originally Posted by JeepCollector

Actually they have the same tow rating - 4x2's are 7400 and 4x4's are 7200. The Dodge Ram 1500 and Durango use the 545RFE with towing up to 8950 lbs in a heavier vehicle.

I didn't catch that. Good call. There are other aspects of the Ram/Durango that allow it to tow more though: Body on frame build bends less than a unibody, spring rates, larger axle (9.25 vs 8.25), etc. Otherwise I would agree the Chrysler mated the 545RFE with more "HD" applications than the Mercedes. Another thing too, is that the Hemi's "gas mileage" would suffer from the shorter gearing as well (the 5th gear in the Merc tranny is shorter than 4th gear in the 545RFE).