09/03/2026
4L70E?
What makes something a 70E ? is it the ISS ? NO 4L60E and 4L65E can have ISS though many do make that mistake thinking that makes its a 70E. 4 Things make a 70E most important are the two shafts shown. These are the heaviest duty input and output shafts GM makes. The Input shaft actually has been Around a while and is identified by the band between the bushing area and seals area and exist in the 300mm shafts in three types, The early generally in the first 65Es then later in the shaft that has the lowered rings but not the reluctor in around late 2004 and then with the 65E and 70e in later ones with the reluctor. Though I have found them in 60E units maybe overstock or built prior.
The OUTPUT shaft a true sign of the 70E also have a band. This one first popped up in the 2006 TBSS 4x4 and Later 2007 up in mostly in the 6.0 trucks.
Thinner 3-4 clutch apply and backing plates to allow an extra friction while still using thick steals is the next sign of a 70E.
Also in the 70E A valvebody plate modification was made to allow the overun clutch to stay on in the D3 position in 1-2-3 gears
So to conclude
HAVING an ISS does not make a trans a 70E
All 2007 up with ISS are not 70E they can still be 60e and 65E and the only good way to tell is the tag identification.
All 70E do have the stronger hardened input shaft and only the 70E had the hardened output shaft and as far as I know only in the 4x4
All 70E do have an ISS. All 70s do have the thinner apply / backing plates for the 3-4 set. ALL 70E have 5 pinion planets like the 65E
I have torn down 2009 and later units that were just 4L60Es
No good external way exist to identify them except that line in the output shaft and being an ISS unit makes it very likely .
But the best way is by the Numbers and letters on the tag on top of case.
THE 70E is most commonly found in the 2006 TBSS and late in ESCALADES and other heavier trucks
Also note 2007 AND 2008 ISS trans are backwards compatible plug in play as long as LS 300M BASED 98 with the FBODY and 2000 with trucks again as long as has 300mm shaft no ni**le at end. And of course the correct 2WD-4X4 set up and linkage shaft.
2009 up are different and cannot backwards swap.
Is it worth it to find one in junkyard? Well it does make a nice starter core for a serious performance rebuild, But realistically ANY 60E built with the right parts- leaks fixed and most important builder who knows from experience what works with what; can be built just as well and just the right HYDRAULIC recipe will handle more than plenty for most people.
In order off importance for a PERFORMANCE BUILD
1-BUILDER I WITH EXPERIENCE DOING THESE OF ACCESS TO THE LONG LEARNED INFORMATION.
2-HYDRALICS the shift kit set up to compromise clutch life to hard parts life. The harder the shift is not always the better.
3-FIXING THE LEAKS AND LORD THESE THINGS HAVE PLENTY NOW DAYS, This is really part of hydraulics but needed to be mentioned separate. Bigger and bigger holes are generally really just compensating for leaks not fixing the true issue.
4-Parts Good quality frictions for the static frictions like FWD - LOW/REV -OVERUN and a host of good choices exist for the 3-4 CLUTCH in the after market each to his own preference here and of course here EXACTLY what you are doing with the car or truck matters on what is best, How many are best, steel thickness application does matter and canned builds are not generally gonna meet every need equally. And what other parts like SERVO and types also matter depending on the application.
Other must are improved sunshell again builder preference here.
Rev input drum I have yet to see one that did not at the very least need to me machined and many times replaced.
Sorry got off on a tangent.
I think I got it all , If I missed something I am sure someone will let me know lol.
I still however stand with since the last 4L60E 4L65E 4L70E were built in 2014 the odds of finding a good one ready to install in a junk yard are getting pretty close to lottery winning at this point.
But hey I still buy lottery tickets so lol
