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Stickied: 4L70E - worth a look?

7K views 15 replies 11 participants last post by  schofell84 
#1 ·
GM has introduced a 4L70E transmissions..

Is this a good replacement tranny fro the 4L60E?
OR
Better to upgrade the 4L60E

D
 
#2 ·
waste....they dont even have a vette servo. I believe it has the 5 pinion planetaries. Either way they are going on 6 yrs old.(so they have been out for awhile)Just build your 60 up better. IMO
 
#4 · (Edited)
Can you expand on this? Sounds interesting. Experience, links, conversion, etc?

Forum search and Stickys came up empty.
 
#5 ·
I doth thinketh he was being sarcastic
 
#6 ·
Not true. In this case. I can be at times.
I have a 5sp allison in my 2500HD. It bolts right up to the 8.1 & has its own dedicated computer. I know these trans could handle the torque an power we want to put behind them.
I would be interested in seeing if these would work.
Maybe Shane has some insight.
I know they are not cheap used.
 
#7 · (Edited)
GMPP catalog - page 152 to 156 gives full details.

I think 4L70 was designed for use behind LS engines--the crank/flex plate position difference may prevent it from being a bolt-on for the GenI/II blocks--there is an adapter package that provides the ability to use later GenIII/IV transmissions on conventional small blocks, including LT1, but it's not 100% clear in the way it's listed as far as the 4L70.

I'm thinking the sheer size of the Allison 5-speed may prevent it's use in the car, without cutting out the tunnel/floor at the firewall and making a new one. Trans crossmember position would probably be different, too, as well as a number of other things--and just like the rest of the Gen III/IV transmissions, an adapter setup would be necessary.

The 4L70 is rated for 495# torque--it should handle just about anything that can be thrown at it.
 
#9 ·
The 4L70E has no performance advantage over a 4L60E. I update my "Race" and "Pro Race" 4L60E's with certain 4L65E parts to add strength. As far as an Allison? Great TRUCK transmission, but as already stated, it's too big and heavy to have any benefit in a performance vehicle. This closely related the the misconception that a 4L80E is a good performance transmission. We had a few hard headed customers 15 years ago that thought the 4L80E would be better than a 4L60E. EVERY car we built them for slowed down ATLEAST 2/10's in the quarter mile. We ended up swapping most back to '60E's...Or the customers got so disgusted that their cars were now turds that they sold them.

Frank
 
#10 ·
DEAD ON!! I use some 65 and 70 parts in the 60 but thats all you need.

I guess only racers think about power loss but if you care about ET then you better care about power loss. It's easier to not have to figure out how to make more power when you can reduce power loss behind the engine. A 4L80E eats power and you cant make up 2 tenths in a better 60 foot launch so even a slower 60 foor by a little will result in a faster ET in the full run.

Ramdom thoughts but thats one reason a 60 is still in my car.
 
#16 ·
Would 4l70 hard parts swap (internals)? Next question being cost effectiveness...
 
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