Thread: Beefed up 4T65E-HD?

What would be the easiest (and cheapest) way to beef up the 4T65E-HD? Any one mod that will help it survive longer?

idk to buy one from one of the supporting vendors like triple edge performance

No easy way other than buying a several thousand dollar built trans? lol

Nothing really, unless you actually open it up. Like doing more than just a shift kit.

With the 4t65e, you don't get "easy" and you definitely don't get "cheap"

Shift kit is a good start, but after that....

Originally Posted by Dadkota

Any one mod that will help it survive longer?

Decrease the weight of driver's right foot.

What do you want it to hold?

Stock power, dollar shift kit, some fluid and some gaskets
Turbo, 600 HP north of 8 grand DIY, 10 if you pay a shop. (Ask me how I know, hint, I did it. And it still broke.)

I was about to start a similar thread when i saw this one. Hate to hijack, but my question partially answers his, so i didn't think the OP would mind.

I got a 99 stock GTP, need a transmission rebuild.

To the OP, I think you're gonna be in it for a total rebuild to make it truly stronger. I'm going to try to rebuild mine myself, and also looking for ways to make it better without going north of 8 grand like Adecker. Here's what I've found so far, hopefully someone else can provide more direction.

These transmissions were updated a few times through the years, including electronics and hard parts. The electronics are not interchangeable, but the improved hard parts are. ( I think) Early models commonly had failures resulting from stripping the splines off the 4th clutch hub. In either 2003 or 2004, GM solved the problem by using one with heat treated, hardened splines. Also, the reverse reaction carrier was changed a few times as well. Some of them have rectangular or oval shaped holes in them, and others have circular holes and the castle top part is heat treated and hardened. I don't know what years though. I think there were more updated parts than those two, but I'm not totally sure yet.

My hope was to identify more of these parts that were changed through the years, figure out what years the changes occurred, and pull one from a junk yard that, hopefully, has them all. Likely from an 04+. This way, I can get some practice in taking it apart and putting it back together before I try it on mine, and hopefully salvage some of the better hard parts and swap them into mine, resulting in a better transmission. Does anyone have more info on this?

Even though it doesn't make the transmission truly stronger, I've read this about modifying it in search of quicker shifts, which would add longer life. Of course there are shift kits, TransGo seems to be the most popular, although Superior makes one also that is said to be very good. I've read you can insert washers into one or more of the accumulators to improve shifts, enlarging some of the holes in the valve body spacer will help improve shifts also if done correctly. Those things can be done without removing the channel plate, which makes them "easy" I guess.

Using oversized steels in some of the clutch packs also helps improve shift feel and speed, but by time you get to that, you're in there and it's pretty much overhaul time. Lastly, according to the W-body tech page at the Overkill motorsports site, if you have a GTP, you can swap from a 258mm torque converter to the smaller and lighter 245mm torque converter. Will claims in his experience that this will put less weight on the input shaft, and therefore make it last longer and with careful selection of the new converter a performance gain can be had. To do that, you also need the flex plate from a N/A 3800 as well he warns.

If my info is wrong, someone please correct it.

While most of your post is true, the ends to not justify the means. In other words, you could go get a brand new 2006 4T65E-HD with all the fancy redesigns and it's still going to have two major fallbacks.

The Input Shaft:
It's puny. It can break on a lightly modded 3.4 setup with sticky tires, GM may as well used a tooth pick in there
The Chain:
Its off a peddle bike. Okay not literally but again may as well be

Doing a full rebuild with sonax parts (3rd, solenoids etc) or better yet a kit from TEP and adding a 300m input shaft and 7/8, GXP or 1in chain is the only way to make things happy. Your torque converter options are stock or Precision Industries custom.
A mild builder would just do a TEP rebuild with a 300m shaft and a 7/8 chain,
a turbo builder better have a 300m or better (GMR 800,1200), a 1in chain, stage 2 TEP rebuild, a PI converter and if you are truley dead set on spending more than the car is worth having dave beef up the case with his fancy brace.

Other transmission options:

Manual swap an F40
Swap a 4t80 in (Promising)
Swap to RWD (Cool)

Originally Posted by Daveliz99

I got a 99 stock GTP, need a transmission rebuild.

Gemini (V8) chain
NEW PNH torque converter
Master rebuild kit - New frictions, steels, seals, gaskets, and filter
Oversize 2nd steel plates x2
Molded 2nd apply piston
Molded 3rd apply piston
Borg warner PCS
Borg warner TCCS
AC Delco shift solenoid x2
Superior AFL valve repair kit (No special tooling required)
Superior valve body kit (No special tooling required)
Sonnax TCC relief valve
Sonnax differential lube tube clamp
Trans-go shift kit
Hardened 4th clutch hub
Lube dam

Plus any other odds and ends that are broke or out of spec.

The V8 chains are all that is out there for a stock replacement BTW, so unless you get ancient stuff from a dusty shelf it should be a V8 chain. Easy enough to tell.

Personally, all the valve body fixes Brandon listed plus are done when you send your valve body/spacer/channel plate to TEP. It's well worth it. I think Brandon also means to add some thicker steels in the input and 3rd areas as well. Getting the stock clutch pack setup can leave too much slop in these areas.

The GXP transmission does have some slightly better parts, but not all of it.

Overall the cheapest/best way to not hurt your transmission is to never turn the key.

My trans is fine right now but I would like to throw slicks on for the track and I'm worried that will be the failing point. I have very light mods, full exhaust, intake, pcm, 3.5 pulley to name the major ones. I have heard about the input shaft and chain but they seem quite pricy to do. If the only cheap way not to break it is by not putting slicks on, then so be it lol how hard is the 4T80 swap? Obviously not direct bolt in otherwise everyone would do it haha

Originally Posted by BillBoost37

I think Brandon also means to add some thicker steels in the input and 3rd areas as well. Getting the stock clutch pack setup can leave too much slop in these areas.

I couldn't find any "off the shelf" parts to tighten up the third. There are 2 different thickness internal splinted clutches (0.080" and 0.082" HE) but because the clutches are bonded to the steels, there's not much you can do with the stack up. At least nothing I've found. (?)

There are different thickness input steels available, but you'd have to go the a 10pc. clutch pack to use them. Haven't got there yet on my build. I do plan to document that. There's also some special snap ring. I'm looking into that also.

The trans I built for my father in laws stock GTP had only the parts/mods listed, and it feels heaps better than any stock unit.

Originally Posted by BillBoost37

Overall the cheapest/best way to not hurt your transmission is to never turn the key.

That hurts Bill.

Use 4T60 steels ... they have more thicknesses

I'm not only a responder.. I've killed too many "built" transmissions.

Originally Posted by BillBoost37

Use 4T60 steels ... they have more thicknesses

We're talking about the 3rd, right?

If so, does that change it to a more traditional friction/steel/friction/steel setup, or is it a variation of the 4t65e's bonded internal/external splined clutch/steel setup?

I'm forgetting at this point..

Not a problem. I appreciate the input. Going to the trans shop on Friday for more parts. I'll see what we can put together...

End hijack

Hijack is all good lol, every post on here is me learning something new haha

I might just have the hole sizes in dropbox.. or in the trans info link thread.