Last weekend I had my Trailblazer SS tranny built by a reputable local builder, he does a lot of 4l60 mild rebuilds and Allisons. He had never built a 4l70 and I had a very complete list of all new parts (see below). Also, he didn't install the 2-3 shift valve because the part was for a 4L80E, and since the trans already had a beast sunshell, hardened piston rings, and a Transgo iso converter valve he didn't install the new ones. The first time he put it together he couldn't get it to shift to 2nd, so he pulled it and took it apart and thought he fixed it. I drove it very little the last couple of days since I was waiting on my new tune. I did get on it a little and noticed that the shift was not very firm and it did have a tune in it just not for the converter lockup. Then today I had to drive like 15 miles and it really started to fight to get 2nd, basically just cruising it starts revving and wont shift unless I let off then it shifts. I let it rev to 4k a couple times to see if it would shift and wouldnt until I let off. I installed the new tune, which has the lockup parameters tonight and it does the same damn thing!What the hell can this be?!? I doubt its the converter, its brand new. Bad seal or gasket somewhere? The weird thing is that it worked for a couple of days (just not firm) and then just started this rev bull ****. Seems like while revving its not trying to shift (not slipping) but as soon as I left off it shifts... Someone please help me with suggestions, I am taking it back to the builder tomorrow and would like some feedback, THANKS.

Phoenix 3200 stall
Transgo HD2 shift kit with custom valving
Sonnax updated 2-3 shift valve
Circle D Input drum reinforcement sleeve w/ billet piston
3 aluminum accumulator pistons w/ hardened pins
Corvette servo
"D" rings for all accumulators and servos, provides better seal than teflon
Special low wear check *****
8 friction Borg Warner 3/4 clutch pack w/ Kolene steels
29 element Borg Warner forward sprag
Alto Carbonite 2/4 band
Transgo high RPM pump kit
Wide sun gear bushing
Beast sunshell

 

to the top, really need some opinions. Thanks

 

Being that your builder had an issue with the 1-2 shift from the start that is the first place he will need to look. Either a servo, accumulator, or a valve in the valve body would be my guess.

On the sonnax HD 2-3 shift valve that was for the 4l80e, it might have been miss-marked. I ran into the same issue a few months back and they were labeled wrong.

If the valve looks like the one in this picture it is the correct one. Vince

 

Thanks Vince! I will tell him what u said, he was out of town this weekend so he will be working on it today. He is going to check the electronic shift module just for giggles

 

**UPDATE**
My builder pulled the servo and noticed the person who installed the servo (before I owned it) welded a bb sized ball on the end of the servo pin to apply more pressure. Knowing that it had a vette servo he didn't see that the first time. When installing all the shift kit parts apparently there is a washer that does the same thing as the bb, and when he installed the washer there was too much tension on the band causing my new band to burn up. He is going to go through everything and double check everything and also install the mislabeled sonnax 2-3 valve (thanks Vince).

When I swing by tomorrow I will take pics of the welded bb...

 

Make damn sure he uses Dexron 6

 

He does, and since the band burned up he will putting new fluid in for the 2nd time in a week

He does about 40 4L60Es a year and the occasional 4L70E (mine was the first extensive 70 he's done). This guy has been great about doing everything it took to find out what was wrong and the issue turned out to be a previous moron.

 

Just curious as to why you say this? the guy that built my tranny said not to use dexVI and only dexIII. im running the blue bottle Mobil ATF DEX/MERC

 

I don't know why he would say NOT to. Dexron VI is backwards compatible and I actually put it in my trans instead of III because they gave my sister VI instead of III. It's a better formula that was created to meet the demands of newer transmissions.
The new formula reportedly improved Friction Stability 100%, Clutch durability 120%, foaming resistance 150%, oxidation resistance 100%, and maintains viscosity stability while Dexron III breaks down over time.

While you guys obviously dont have reason to worry about warranty, GM will NOT warranty a new transmission that had Dexron III in it.

 

Ok here's my question, how did he miss the pin being welded on if you supplied him with D-ring seals for the servo? The servo assembly needs to come out of the case to change those seals. It sounds like your build wasn't done properly to begin with, IMO the trans must come apart 100% for a build-up of any kind. Good luck.

Chuck/FLT