ISOrabbitsfoot

I'm new to the site and any/all transmission details, so any help would be very much appreciated. I noticed that there are many 4l60e swap to 4l80e but Im asking if an 07 silverado 4x4 would require less modifications to complete the swap? Also, after a hard launch in first I was climbing over 5500 rpms then all of a sudden it felt like the tranny (4L60E) popped into neutral. I finally rolled to a stop and found out I didn't have any forward gears except for reverse and park. It didn't make any loud clanking or banging noises, it just felt like it popped into neutral. I checked the shift cable and it seemed to be working fine. Sorry if this post seems repetitive to other posts. Thanks for all the help!

mrvedit

Try putting the shifter into [D1]. If you can start in [D1], then manually shift into [D2] and [D3] and finally [OD], but get nothing when starting in [D3] or [OD], this indicates that the forward sprag has failed.

ISOrabbitsfoot

I tried starting in all gears, only starts in park and neutral. No forward movement just reverse.

ISOrabbitsfoot

This is the truck that the tranny failed in. I post this because I need your input on what tranny would best suit it? 2007 ltz, 5.3 jasper motor with work done in it (440 rwhp)

mrvedit

First I would not even think of putting any kind of stock 4L6xE/4L7xE into the truck. One of the "mid range" 4L65E from FLT, RPM or PerformaBuilt should be able to handle your needs; make sure it is ordered for a 2007 so that it includes the Input Speed Sensor (ISS). It will probably be in the $3000 range.

No one has yet posted the details of installing a 4L80E into a 2006+ vehicle that came stock with a 4L70E with ISS. Perhaps the ISS on the 4L80E is compatible with the ISS on a 4L70E and it is a non-issue.
I suspect a 4L80E would easily fit your truck and a swap would not cost much more than $3000, making it a better choice than even the best 4L65E.

ISOrabbitsfoot

Also I failed to mention that the 4 wheel drive doesn't pull at all, it's like it isn't engaging. Could that be the forward sprag causing that also, or the transfer case?

mrvedit

Even with the forward sprag failed, the car will drive almost "normal" in [D1] and [D2] because the overrun clutches are engaged and can handle a limited amount of power.

Since you say you have Reverse, then the converter, input shaft, pump, sun shell, rear planet, low/reverse clutch and output shaft are all intact. There are accounts of the sprag failing in such a dramatic way that the input drum is damaged and all forward gears lost, or other damage to the input drum.

While I'm sure the pro builders would have more precise diagnosis, it should be pretty clear that the trans needs to come out and be replaced with something stronger. It is not something "simple".

We have another current thread where the OP lost all gears but has good line pressure. There is a possibility that his problem is a bad converter, but since you have Reverse, your converter is fine. (Well might need to be sent for opening/cleaning depending upon the trans problem.)