T56 Service Manual
Tools needed:

• Torque wrench
• Punch set
• Good Snap ring pliers
  -inner and outer, Sears carries a decent selection
• Jaw Pullers, at least 6" & 8"
• T40 torx bit
• Assembly lube/grease
• 2.5" PVC pipe
• Marker
• 4qts ATF + some to soak the blocker rings, either save some that came out or another qt.

Disassembly:

Remove shifter:

Remove:


Stand transmission up with the input shaft facing down,
-put the input shaft through a hole in a table, the bellhousing and a couple blocks also works

Remove:
Start tearing down the beast:
Remove:

-a bit down the shaft
5/6 gear removed

RemoveRemove:(shift guide bolts)



after the guide plate is off, punch out the rolling pin holding the front offset lever (below)


Now we are ready to take off the main case.
The underside of the front offset lever contains a spring loaded ball that rides in the shift detent assembly. When pulling the main case off, hold the end of the offset lever down as the shift rail comes out. It's easier and also helps the ball not go flying off somewhere.

Slip the main case off.


Take a moment and look how the shift selecting pin and interlocking plate work together.

Note the vertical slot on the 5/6th shift rail lever (left,#144 slot not shown) and the horizontal slot on the interlocking plate (right,#156). We'll have to line these up when the shift guide bolts go back in.

Remove:
From here the mainshaft must be take apart from both ends, a divider can be seen after removal of the 3rd gear.
Flip the mainshaft upside down on the stubby end, (right side of pic below)
-leave the bearing on unless you're replacing it.

(Starting left- large tapered bearing, 1st gear, 1/2 synchro, 2nd gear, 3rd gear, 3/4th synchro. Divider pointed out)

Remove:Now we're done with the stubby end, flip the mainshafter over.
Remove:
Tape them so they'll stay together. (Jimmy rigging this sucks, the_merv builds a better unit on pg5)

note, the 6" puller is oriented wrong in the first pics

Continue removing:Mainshaft Disassembly complete:


Back to the Countershaft Extension:

Remove:
Continue removing:Countershaft disassembly complete:



Synchros:

-There's slots on the blocker rings that must line up with the keys upon assembly, it's self explanatory when you look how it goes together.
-You'll notice in the pics that I've marked all the blocker rings and synchro sleeves, so there's no guessing involved.

The reverse gear synchronizer key retainer:

 

Assembly:

Clean the splined parts and grease them up prior to assembly. This way you won't need a press, some will go on by hand or with minimal effort from a hammer and the PVC pipe.
Soak the blocker rings in ATF fluid for 20 minutes or more prior to installation.

Countershaft:

Now begin putting parts back together:!(important) below - correct orientation of the needle bearings, (grey left, brown right)


Countershaft Assembly Complete:

Mainshaft Assembly:

Starting with the longer end:

-scrape off the old silicone


Apply lube to the ball to make things stick.

Slip main case on and position the front offset lever to sit on the ball while sliding the shift rail through.
(Note the ball sticking to the detent with grease)

-front offset lever not shown.

Here we are


-a bit up the shaftSlide the tail housing on. If you can't get it quite on, it's probably because the 5/6 shift rail isn't lining up with the tail shaft socket. Use a long thin tool to pull it right and towards you; when you get it lined up, it should fall right into place.
Drive the roller pin back through the shifter saddle.

Torque Specs:-corrections/input welcome


%%% edit %%%
A number of people have contacted me about fixing the leak between the tail housing and the main case. Here you go.

Fix Leak Between Tail housing and Main Case

Remove shifter:

Remove the 4 hex perimeter bolts and remove the entire shifter as a single unit
Punch out Roll pin in shifter saddle and set aside.

Stand transmission up with the input shaft facing down,
-put the input shaft through a hole in a table, the bellhousing and a couple of blocks will also work

Remove:

(8) 5/8" bolts from the tail-housing and lift tail-housing off

clean surface, reapply silicon

Slide the tail housing on. If you can't get it quite on, it's probably because the 5/6 shift rail isn't lining up with the tail shaft socket (look at the inside of the tail housing and you'll understand). As you're sliding the tail housing on, use a long thin tool to pull it (the 5/6 shift rail) towards the right, and towards you; when you get it right, it should fall right into place.
Drive the roller pin back through the shifter saddle.

bolt up tail housing bolts to 26ft.lbs
put the shifter back on. 4 perimeter bolts @ 15 ft. lbs

Pliers, external
internal

 

Sticky Worthy!!!

 

very nice

 

great write up

 

Very nice! Sticky for sure.

 

I vote sticky for those do it yourselfers

 

Very nice writeup!
I've rebuilt a couple of these and there's really not much to it........HOWEVER---the 5/6 driven gear on the mainshaft will determine how smoothly your rebuild goes. You may be one of the lucky ones and the gear will come off easily using a puller without damaging any teeth, the first trans I rebuilt was like that. The last one I did was an absolute nightmare.....I broke 2 heavy duty pullers, several teeth off of 5th gear and finally ended up having to cut that f*cking 5/6 gear off (keep in mind that gear costs $200). It also took heat and a 20 ton press to install the new gear......so be aware DIY'ers, that scenario is a possibility.

The only other advice I'd give to a first time rebuilder would be to lay all of the parts out in the order you take them off so everything stays organized, and get a copy of a service manual....the exploded views will make sure you get everything back where it's supposed to be. Also, don't install the old snap rings......a new kit is only $30.

 

IF you replace a synchro assembly..Is there a specific side ...how to tell or does it mater

 

Wow, that seems rather complicated. There's a lot more crap in there than I previously thought. I have a fealing my trans is crapping out on me though. I'll keep this in mind when it comes time to rebuild it. Thanks for the write up.

 

It doesn't matter on the side, the reverse can actually be flipped for a fresh face. Just be sure to line up the detents on the inner part of the sleeve with the humps on the keys.

 

got my heads/cam car sitting dead in the water right now because the tranny is locked in third and have been thinking about doing this.

To rebuild the tranny to say, hold a 1k hp (looking to the future), where can a master rebuild kit be bought to bring the t-56 up to spec to handle that kind of power and what kind of money would i be looking at spending?

now that this is up, i think i'm not the only one with this question.

is this also saying that to rebuild a transmission, this is all that there is to it? I was always under the impression there was alot more to it.

 

awesome writeup!

 

Wow, that doesn't seem as bad as I thought. Did you replace any of the bearings? I've "heard" that it is not recommended unless they are bad or damaged.

 

I am really glad to see this writeup since im in the process of doing this myself. honestly, I really do appreciate anything I can find. I still dont understand why someone who is proficient with the T-56 hasnt made a rebuild video and sold copies of it online yet.

However, on a side note, and strictly coming from a guy who is gathering whatever he can from various write-ups online, Ive found an article where Joe from sixspeedsinc.com is photographed while rebuilding a T-56, and he makes a point in one photo to tell you that the small grooves that run around the circumference of the sliders should always point towards the front of the transmission, I.E. towards third gear on the mainshaft. Take it for what it's worth, I personally couldnt tell you jack about these transmissions based on experience, and I mean no disrespect by coming in and adding any doubt to your answer above.

if you have any interest in that rebuild article, search for "Joe Amber t-56 rebuild" under google and you should find the article by GM High Tech Performance as the first thing that pops up. Maybe I misunderstood the meaning of the caption on the photo, even though it is cleanly written and seems straight cut.

 

excellent, I may give this a shot! How much for a "viper spec" rebuild kit?

 

Yep, you are supposed to do that. I'll put that back in. I wrote it up a couple of months after the rebuild, so my memory was a bit off. (Questionable, read Ceissus)

thanks

edit: As I recall the grooves lie only on the (1/2) or (3/4) slider ring. It maybe both but definitely not the reverse.
This sounds right, they do look symmetrical and I don't think the grooves serve any purpose.
Bearings aught to be good for the life of the transmission and are not part of a typical rebuild. Though depending on your issue, say if you run it dry, they may need to be replaced. Wear and tear parts, blocker rings and shift pads, generally wear most and are the focus of a typical rebuild. Blocker rings have friction lined surfaces; they are the clutch like parts that allow for smooth engagement. Fork pads should not wear, but the stock units are plastic; they will wear when shifts are forced, usually when hydraulic (clutch disengagement) issues from lack of bleeding come into play.
As a side note: This is also why I did not include anything about checking end-play. If the bearings are not being replaced, then you're not changing any tolerances for between the shafts/bearings/races; we're just replacing parts that ride on the shafts, blocker rings, synchros, etc. Feel free to argue this point. If you swap bearings then yes, it would be absolutely necessary to check for end play and shim it properly for bearing preload.

(Credit goes to RestoRoc89 who covers this on pg5)

To check end play, you'll need:
-Shim kit to set bearing preload
-Dial indicator & a multi-position magnetic base with fine adjustment (can be had at harborfreight),
-Threaded end play tool to thread into the countershaft

 

Rebuild kits (without bearings) should include the following:
Synthetic lined blocker rings
Synchro springs
Seals
Stock keys
Plastic fork pads
Shifter saddle bushing, (aka shifter isolator cup)


If you want to build it above stock specs, 30 spline Viper output shafts run at about $250 as opposed to our 27 splined mainshafts. GM updated the MM6 shaft in Z06's to a 32 spline unit as well as a one piece countershaft; that's probably a better bet than viper spec.

-other upgrade parts
Billet keys, replaces stamped parts
Bronze fork pads, plastic pads are the weakest part of the transmission and a source of many a problem (highly recommended)
3/4 Steel fork, replaces aluminum fork, common problem (recommended)
Synchronizer assemblies (1/2) (3/4) (5/6), reverse can be flipped for a fresh face
%edit, new part available
Bronze shifter bushing isolator cup (recommended)

Synchros replacement will depend on inspection; the need to replace is indicated by grinding gears. Although the service manual says it may also be due to; bell housing misalignment, bent shift forks, clutch disengagement issues, bad pilot bushing, or damaged gears. Section 3 in the service manual has a comprehensive list on inspection of parts for reuse, or replacement. According to the manual, even chipped gears may be reused if the chips are on low stress areas (tips). Instructions are detailed for repair by grinding chipped edges. (This sounds sketchy, but looking at the animation of gears meshing, it's clear the part of the gear tooth furthest from the center has little involvement in torque transfer.)


Bearings are optional, expect to shell out $250+ over the cost of a basic rebuild kit for Timkens, cheaper brands can be had for less.

There's a parts supplier who's well known here on the board, but they're not a supporter of tech so they'll remain unmentioned. T56 rebuilds is another supplier, a sponsor and known for having great customer service.


There's a debate over the use of certain synthetic fluids, it seems to tear down the stock paper based lined blocker rings but the carbon/kevlar lined rings don't seem to have a problem. As of 02' all T56's got the updated rings.
"Last year the 6-speed received carbon blocker rings on its synchronizers, increasing the durability of the transmission." -That was printed in the 03" model year summary

Once you tackle it there's not much to it, organization is key. If you have a lot of difficulty getting a particular gear off, get a machine shop to remove it. It's not worth breaking parts.

 

thanks for the right up. very nice piece. definitely sticky worthy.

 

man, this is just what the doctor ordered...I just picked up a TA on Tuesday that pops out of reverse...I hadn't rebuilt a tranny since school 20 years ago, so I was a little intimidated by the T56. Looking at this write-up, it doesn't look that bad. good deal! Thanks for taking the time to do it!