If you just have no 4th gear you might be able to fix it in the vehicle, the 4th gear clutch is the first thing you come to in the trans after removing the side cover and the valve body, get an ATSG Book from Transtarindustries.com, it will cost you about 30 bucks, study the book, the 4t'* have a problem with the 4th gear support device, they tear the splines off, it is not a hard part to replace with a little studying of the book. The ATSG book will show you the part and how to get to it. Transtar also sells all the parts to fix it, rebuild kits, convertors, etc. you can download a parts list on their site, gives you some nice exploded views of the parts. Here is a link to the download page, http://www.transtarindustries.com/ca...D=1&strIDS=1,5

Download the 4t65e catalog, it will open in adobe, the part that usually fails is part #206 on line G. Page 117. It is the 4th clutch hub and shaft assembly.
Hope this helps.

Thanks, I've purchased a new ATSG thru E-bay for $16.07 (includes shipping). Your info was just what I was looking for. Fix the problem w/o removing the tranny or paying someone $1400+ to do the same thing.

Glad to be of help, just take your time, think it through, and most of all keep things really clean.

ATSG Manual arrived.

Main steps are remove:
1.side cover
2. wiring harness
3. oil pump
4. pressure switch
5. valve body
6. oil pump drive shaft
7. final drive housing
8. differential (final drive carrier assembly)
9. output shaft
10. detent spring & roller assembly
11. oil dam
12. input speed sensor
13. channel plate
14. 4th gear clutch plates
15. 4th gear clutch hub & shaft
16. Insert new 4th gear clutch hub & shaft
17. Reassemble

Correct? Can I skip steps 7 thru 9? What gaskets can be reused? Side cover only? Should I disassemble the valve body?
68k on transmission. Should I replace anything else?

These are the correct steps, 7,8, and 9 can't be skipped because the output shaft runs all the way through and must be removed. the only gasket you can re-use is the side cover, new o-ring seal is needed for the final drive cover on the passengers side of the vehicle, new channel plate gaskets are needed, also new o-ring gasket for under side cover, this o-ring goes around the axle shaft seal area on the inside, when you re-install the side cover make sure you use a small amount of rtv gasket sealer to hold the o-ring to the side cover or it will fall out of place when you put the side cover back on, new valve body gaskets are required, I would not take the valve body apart, I only do that when I have massive failure, foreign material can stick the valves but I think you will be ok, there are a lot of valves and springs in there and if one gets out of place it will cause you a lot of trouble.

Thanks for the info, very valuable.

Any recommendations on where to purchase such seals? In one of the of the above posts, I can go to tripleedgeperformance & purchase a complete TransTec overhaul gasket & seal kit for $70.

Is this the best way to proceed?

You could go there or Transtar has kits available also.

I'm tearing down a 4T65E-HD right now. I'll post a bunch of pics tomorrow (although I really started taking the majority of my pics at about step 14 on your list). I'll also have some warnings about some difficulties I had.

As I recall, to go as far as you are talking about going, the only special tools (beyond metric sockets) you'll need are T30 and T40 torx bits.

I took a pic of the 106k mile 4th clutch hub, and it will show you why you need the newer-style hardened part.

I'll also take some pics of the 4th clutch steels that may make you want to get new 4th clutch fibers and steels, too.

You probably won't be able to avoid steps 7 through 9...I found that in order to replace the 4th clutch hub and get it to seat straight in the inside teeth of the input sun gear, I had to go in with a long screwdriver from the diffy side and push upward on the inside of the input sun gear (it wants to "sag" a bit, at least when the trans is sitting horizontally).

As promised, here is some coverage of my teardown of a 1998 Regal GS 4T65E-HD:

To get the side cover off took a deep 10mm (and a deep 13mm maybe?) plus a T40 torx bit. Check the condition of the side cover gasket, it may be reuseable (no pics of mine, sorry, but I plan on reusing it). These do not come in kits, but have to be ordered separately (and are not cheap):
http://intense-racing.com/Merchant2/...ategory_Code=T

Here is a pic of the 4T65E with the side cover off (not my trans, I got this pic off the web):


The pic above shows the harness and all the pump and case cover bolts you have to remove. You will need 8mm, 10mm sockets and a T30 Torx bit for these.

Warning 1:
The red circle shows a bolt I rounded off. These bolts can be tight, and they are shallow-headed flanged bolts (easy to mangle). That one is a Grade 9.8, black oxide-finished, M8-1.25 50mm (25mm threaded), 10mm hex head:



I got it out working my way up to 9/32" reverse drill bits.

Warning 2:
The little clips on the electrical harness solenoid etc. connectors are very brittle, and I broke every last one of them:


If this happens to you, you can get a replacement harness, but make sure you count the pins in the main connector to get the right one (can be 14, 17 or 19 pin depending on year and car model). This one (from a 1998 Regal GS) is a 14-pin:


Your harness from a 2000 Bonnie will be different, because I believe you have internal mode switch (IMS). Intense sells a harness, but I do not know how many pins it is. My research shows that there is a "universal" 4T65E internal harness available that will work whatever number of pins your original harness was:

http://www.bulkpart.com/Merchant2/me...oduct_Count=13

Here I got the pump, valvebody and case cover off, showing the gearset, reluctor (on the drive gear, left), and 4th clutch hub (in the driven gear, right):


Be sure to check for chain stretch. I'm sure your manual gives the procedure. Mine says at least 1/8" clearance between the chain (pushed down taut) and the case (just above where the lower channel plate gasket is in the pic above). This 106k mile chain had 1/4" clearance and no visible problems on close inspection, so I plan to keep using it.

Keep an eye out for the lube scoop under the driven sprocket, make sure it stays in place:


Yours may be "natural" in color if you are n/a with 35/35 tooth drive / driven gears (the -HD'* are 37/33)

Sorry I did not get pics of the valve body; watch for the checkballs, especially if the trans is horizontal. I'll get pics of that later if you want. You will need new valvebody separator gaskets or the newer-style separator plate with gaskets already bonded to both sides...you can get that from Intense (et.al.):
http://intense-racing.com/Merchant2/...ategory_Code=T

You'll need new upper and lower channel plate gaskets also, which are available from Intense (et.al.):
http://intense-racing.com/Merchant2/...ategory_Code=T

If you decide to get an overhaul kit instead, these gaskets (and much more) come with it:
http://intense-racing.com/Merchant2/...ategory_Code=T

Warning 3:
Check the condition of the pins on the reluctor wheel (mine turned out fine):


Make sure they are nice and tightly pressed in. A member on another forum recently lost a chainset to a reluctor wheel that fell off because the pins fell out.

Here'* a pic of the backside of the case cover. In my case, the 4th clutches and steels stuck to it and came off with it (right):


Watch for the alignment pins between the case cover and case:



Warning 4:
I had a "mystery clip" hit the ground when I took the case cover off:


I believe I once saw a TSB about "extra clips" being found in 4T65E transaxles; I have to find that again :?

Anyway, to fix your 4th clutch hub, all you really have to do is pull it out of the driven gear, and install the new hardened hub; although, as I stated in a previous post, I had to go in from the diffy side (with diffy and output shaft removed) with a long screwdriver (taped end to prevent scratching bushings) and push upward on the inside of the input sun gear to get the 4th clutch hub to line back up and seat.

Why replace the 4th clutch hub? Here'* a used hardened hub from a 2003 trans (left) versus the 106k mile one out of this 1998 trans (right):


Once those unhardened teeth shear completely off, no more 4th gear. The hardened hub started in 2003. I think the 2003 hub I have is useable.

You can get a new one from Intense (though GMPD may be cheaper):
http://intense-racing.com/Merchant2/...ategory_Code=T

Warning 5:
When you button it back up, check the condition of the teeth on the pump shaft at the torque converter end. Here'* a used pumpshaft from that 2003 trans (left) versus the shaft from the 1998 trans (right):


The 1998 shaft is clearly more worn than the 2003 shaft. The 2003 shaft is more worn than I'd like, so I'm probably getting a new one. Intense sells them (though GMPD may be cheaper):
http://intense-racing.com/Merchant2/...ategory_Code=T

Warning 6:
Take a close look at your 4th clutches and steels. I've read that they like to burn and leave "leopard spotting" on the steels, and that'* what I saw:


If you want to be pre-prepared and get 4th clutches / steels, Intense has that too:
http://intense-racing.com/Merchant2/...ategory_Code=T

That'* all for now.

Thanks for the info and photos. The manual just has drawings.

Your posts will be very helpful to me and others too as Bonnevilles are traded & sold from "I'll just buy a new car" owners to "I'll pay to have someone fix it for me" to "I'll fix it myself" owners like me. Then it moves on down to high school & college kids who (1)have Dad fix it, (2) pay someone or (3) decide to learn something by fixing it themselves.

BTW Couldn't one just push the pins out of the broken plastic connectors and purchase replacement connectors at NAPA instead of purchasing a new harness?