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Hello! I am new to the forum! I own a 2000 Chevrolet K2500 (not Silverado) ext cab 4x4 with a 454 with 60k miles on it that I picked up damaged and I have since re-built it. I also own a 1999 GMC K2500 4x4 Suburban with a 454. I must say that I enjoy the 454 and 4 speed combination. I dont do any heavy towning at all with these 2 trucks, these are daily drivers. I am posting on this forum is to ask the question why GM does not offer the 4 speed transmission with the new 8.1L big block in the 2500 HD pickups? I have tested out a new 2500 4x4 Suburban with a 8.1L and the 4L80E/4-L85E transmission combination. It had more power and torque then my 99 Suburban and 00 pickup. I then test out a 2500HD pickup with a 8.1L and Allison transmission, Extended cab (same configuration as my 2000 pickup). After driving the 04 pickup with the Allison, the 04 Suburban with the 4L80E/4-L85E transmission combination and my 99 Suburban and 00 Pickup have more lower end torque then the 8.1L and Allison transmission. I was very disappointed with the 04 2500HD pickup. I did not like the fact around 45-50 mph that the Allison shifted between 4th and 5th. It was up and down the entire test drive. It would be nice to see GM offer the same combination of the 8.1L and the 4L80E/4-L85E transmission combination that is in the new 2500 Suburbans with 8.1L as a option in the new 2500HD and 3500 pickups as a option instead of having just one transmission option. Some of us like the big block as a daily driver.
 

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The 8100/heavy duty 4 speed auto is also available in Avalanches. I am not sure why it is not available on Silverado, but I bet is has something to do with trailering capacity.
 

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Yes the Allison is the tranny you get on the silverado 2500HD or 3500 with the 8.1L because its why it has a towing cap of 12,000lbs with the 3.73 axle or the 4.10 , whereas with the K2500 suburban with the 3.73 axle you get 10,200lbs and only with the 4.10 do you get 12,000lbs tow cap. .. And the Allison 1st gear and reverse are almost creeper gears and are meant to get a very heavy load moving effortlessly.
 

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im new to this site and dont know where to turn. i have recently purchased the 2004 3/4ton suburban w/6.0 motor and 4:10 gears. at 1100 mi i had a trans failure. gm stepped up and admitted a recall issue. they replaced the trans with a new one. now at 3200mi i am back in the shop with another trans failure. does anyone else think this is the wrong setup for this truck. or has anyone had a similar problem. gm has given authorization to replace trans again and extended our warranty but that doesnt build my confidence in the vehicle one bit.
 

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? The 4L80e verses the Allison. I would jump on the Allison hands down. If the shifting is that big of a concern then just drive with the tow\haul mode on at those speeds, or opt for a different axle ratio or tire size.
 

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im new to this site and dont know where to turn. i have recently purchased the 2004 3/4ton suburban w/6.0 motor and 4:10 gears. at 1100 mi i had a trans failure. gm stepped up and admitted a recall issue. they replaced the trans with a new one. now at 3200mi i am back in the shop with another trans failure. does anyone else think this is the wrong setup for this truck. or has anyone had a similar problem. gm has given authorization to replace trans again and extended our warranty but that doesnt build my confidence in the vehicle one bit.
I have not been back here in years. I did end up buying a 2004 gmc 3/4 ton yukonxl 4x4, 8.1L, 3.73 gears. two yrs later I sold it to someone who really wanted it since they discontinued the 8.1 in the yukonxl/suburban in early 06 they only made a few. the mielage was poor but a dream to drive it. I bought one of a few 06 3/4 ton yukonxl left when i saw what the 07s looked like.. smae 4x4 but 6.0L with 4.10. neither tranny ever gave me trouble. the order code on the 8.1 4L80E was a MMN and on the 6.0 its a MT1, I beleive the MMN is heavier duty in some aspects. I still have the 06 2yrs and 2 mos later 31k miles no problems at all.. better mielage by far even w/ 4.10 gears.. I tow a big boat and drive 15k miles a year so it gets used alot and its a workhorse... there is a new 6L80E on the escalades and now the 08 H2 with the 6.2L small block which I hear wil be in the 3/4ton yukonxl/suburban fo 09. now for 08 they did put the 6L80E in the 3/4 ton but still with the 6.0L now at 352HP but has a 3.42 gear with no option.
 

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now for 08 they did put the 6L80E in the 3/4 ton but still with the 6.0L now at 352HP but has a 3.42 gear with no option.
But you have to look at the gears inside the transmission.
If I remember right, the 4 speed automatic had 3.04 first, 1.57 second, 1.00 third, and 0.68 fourth gear. If you add in a 4.10 final drive, your total gear multiplier to the wheels is:

12.46 in first, 6.44 in second, 4.10 in third, and 2.79 in fourth.

The 6L80E first four gears are: 4.03, 2.36, 1.53, and 1.15. Multiplied by a 3.42 final drive, and your total gear multiplier to the wheels is:

13.78 in first, 8.07 in second, 5.23 in third, and 3.93 in fourth.

The 6L80E with a 3.42 puts more torque to the ground than the 4L80E with a 4.10.
 

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Earliet Allsion 5spds did not have a selectable 4/5 (overdrive) gear. Newer ones do...nice to be able to control OD. GM does have a tech service bullitin to add a switch to the older units.

I've heard a couple guys say they like the daily driver performance of 8.1L with the 4L80E (2500 sub and Ava) over that of the Allison in the HDs. I try not to drive mine unless working it...cant afford too at 10mpg...
 

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But you have to look at the gears inside the transmission.
If I remember right, the 4 speed automatic had 3.04 first, 1.57 second, 1.00 third, and 0.68 fourth gear.
The 6L80E first four gears are: 4.03, 2.36, 1.53, and 1.15.
4L60/65/70-E: 3.06:1, 1.63:1, 1.00:1, 0.70:1
4L80/85-E: 2.48:1, 1.48:1, 1.00:1, 0.75:1
6L80/90-E: 4.03:1, 2.36:1, 1.53:1, 1.15:1, 0.85:1, 0.67:1.

The 4L80/85-E takes less power to turn and is thus more efficient, however with more gears and a better spacing the recovery RPM helps keep the engine in the fat part of the torque curve.

The 6-speeds do a better job with less rear gear, but with 3.42:1 final gears that 6th gear is essentially useless on all but the flatest ground.
 
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