"auto out-manual in" driveshaft problem

[like2drive]

(1981) Still "getting ready" to swap the auto out & install the Muncie. Came across this problem. Although I have read on other threads that the driveshaft did not have to be modified, from my measurements, it probably will.
The driveshaft for the manual trans. is 1/8 to 1/4 " longer than the one for the automatic. (Have to use the Manual because it has a larger u joint at the trans.yoke)
The Muncie + Bellhousing = 3/4" longer than the THC 350 Automatic.
I'm wanting 1.5 to 2" of "play" or sliding room at the transmission end yoke, the same as the automatic currently has. (this is for suspension extremes that may cause the driveline problems otherwise)
Am I getting ready to have 1" cut out of my driveshaft that I just got balanced and new Spicers installed 2 days ago?
Anyone thats done this on a 1981 could really be a help...maybe
Anyone......? thanks in advance, Jim

[pbcanney]

Well, I'm not to that point yet, but it's good to know this.
I did get a front yoke (I think thats what it is) in the "package" I bought that came with the original 79 bw trans.

One thing I have discovered is the frame mount for the arm that runs from the engine to the frame wasn't included on all 81's. (Unlike the preceeding years.) It was omitted on the automatics.

Luckily, it's available from the aftermarket companies. (both bolt on and weld on)

[like2drive]

thanks for the reply, PB! What are you referring to as the "arm that runs from the engine to the frame"? The Z-bar? (bellcrank). If so, I did have the holes drilled in my frame for that and already have the Z bar mounted.
From another source, I was told that 1/2" of endplay on the yoke should be enough. If that is true, then I don't need to cut the driveshaft. Another point is that, floor measurements like I had to make, are risky because the new tranny might have to have shims to achieve the correct angle at the rear end. Achieving the correct angle can affect the endplay.
I was hoping to have all the details resolved before going to the garage that will actually do the work..."by the hour". The driveshaft will be the last item installed (under the car) and I was hoping to avoid having to wait for any modifications on the driveshaft. Thanks again, jim

[pbcanney]

Is the part I am referring to. I have a mig welder my kids bought for me a few years ago. Maybe it's time to plug it in and learn how to weld

- Paul

[like2drive]

Good show ole boy! Yea, that's the Z bar bracket, bracket for the "bellcrank".

I had two bolts in the predrilled holes on the frame. It's close to the curved section on the frame (I think ) towards the front.
However, on mine, after installing both ends of the Z bar..one in the bracket & the other on the engine block....it seems to me the Z bar is cock-eyed, w/the engine mount "a little" further back than the bracket. I have TWO predrilled holes on my engine for the pivot stud mount (?) and I used the one on the rear because it "seems" closer to being "square" w/the bracket.
I'm not a welder but, don't you have to take precautions not to damage the alternator? or battery? when you weld on a car? good luck, jim

[pbcanney]

anyone with a 4 speed want to chime in on whether the Z bar is off set a little?

[LannyL81]

From what I remember when I had to replace the Z bar bracket (mine was split) there was not much offset, pretty much in-line. How much offset are you seeing?

LannyL81
Tucson, AZ

[like2drive]

I'd say the offset is 1 1/2 to 2". I'm holding off doing anything until the garage that s supposed to make the actual switch next Monday. I want to see how they think it lookes.
If it is futher back on the engine side than the frame side, and it has to be "square" , I have an idea of a simple bracket I can make to get the " right" results. 1"W x 6" L x ~~1/4", two drilled holes for mounting on the offset engine holes, and then drill a hole somewhere in the middle that would "line-up" the Z bar right. How's that? ?? jim

[pbcanney]

Just making sure you're still on track..

got any pix???

[like2drive]

I'm ashamed to admit it, but I had the Z bar bracket on backwards ...well it will bolt up either way..... reversed the bracket and it lined up.

That was a couple weeks ago. Got it to the Trans shop to do the actual swap and have problems. Made previous arrangements, was there w/car in garage at 7:30 AM on June 27, was told would be done in 6 hours and out the next day. its still there...maybe tomorrow.
Thanks for the comments., jim

[bossvette]

FWIW on the Corvette IRS the Differential is mounted to the frame unlike solid axle cars and does not need "play" in the yoke for suspension travel just make sure you have enough engagement on the splines. If your driveshaft is a little longer it will not hurt UNLESS it is up close against the tail shaft.

[pbcanney]

Well, I pulled the automatic out of mine last week. Corvette central had all the parts I needed for the Z-bar and boots and little stuff. Now it's just a matter of getting the team together (uh.. that'd be me) to reassemble the thing with the BW 4 speed.

One pending snafu I foresee is the front part of the (79) driveshaft mating to the 81 driveshaft. The 79 (yoke?) looks much beefier than the 81's automatic.

That and the bonehead that ordered the clutch pack (uh.. me again) ordered a 10 1/2" when it appears now, it's 11.

good help is hard to find around here ........

here's a few pics here:
http://corvette.canney.net/transmiss....html#july2005

[like2drive]

I'm impressed! I hope to one day learn how to post pictures like that. I finally got mine back after 2 weeks...(remember it was promised in 2 days originally)

Yea, its a joy to drive but I'm still ironing out some minor problems...like the shifter didn't line up w/the console. After a week of wrestling w/Hurst for suggestions..(.I bought & had installed what they recommended )and trying to get help from a few great Vette shops I knew (w/o success--too far behind), I finally figured out the problem myself while sitting in the parking lot of an expert who said he'd advise, but couldn't take on the project.

The problem was: the installer put the stick on backwards....it has a small curve at the bottom, and should point towards the passenger side, not towards the driver...that gave me about1/4 to 1/2 inch.
Also...the installer put the mounting block on the passenger side of the stick and it's suppossed to be on the driver side of the stick.(yes, I did give him the directions and a diagram which clearly showed this set-up)

I spent some time w/my son in the Keys last week so I had to stop on the project, but hope she'll be ready in "another" week. thanks for the imput, jim
ps, I am also posting a list of stuff needed for this swap on another post after this one.

[like2drive]

Hope this helps someone...TRANSMISSION EXCHANGE PARTS LIST
1981 Corvette Automatic Removal, 4 Speed Manual Installed
1. Brake light switch
2. Back-up light switch, rod, bracket, shield , screws

3. Pedal pads
4. Clutch and Brake Pedals
5. 80-90 gear oil, 2 quarts (fill to plug..won’t need it all)

6. Clutch fork bearing spring
7. Clutch Fork & Rod
8. Clutch Fork Boot
9. Clutch Fork (#3887177) & Rod Anti-Rattle springs , 2

10. Clutch Pedal Push Rod w/ firewall boot
11. Clutch pivot stud on engine
12. Clutch pivot stud at bracket
13. Z bar clutch return spring, 1 @
14. Z bar frame bracket

15. Zbar (bellcrank)
16. Clutch Disc, 11” (1 1/8“ Dia.-26 spline input shaft)

17. Pressure Plate, 11”; (a BOP- chevy will not work, get Corvette!) Pressure Plate to Flywheel bolts, 6@ 3/8-16 x 1” , Grade 8, Hex Head w/shoulder to prevent movement.

18. Throwout Bearing; use the shorter (~1.25“), not the longer(~1.75”)

19. Pilot bearing (roller type)
20. Alignment tool (26 spline)
21. Flywheel, 168 teeth, (Starter will need replacement) (automatic flexplate is 168 tooth but starters are different)

22. Flywheel to crankshaft bolt set , non-standard, “special“! 5 @ THIN Hex Hd, SHOULDER bolt, 7/16-20 x 1” w/internal star washers.

23. Bell Housing (ID#3899621) w/new ball stud 6 bolts, w/2 dowel alignment locations on sides. **(Bellhousing and transmission must be in alignment) Phasing

24. Bell housing to engine bolts, 6 @ 3/8-16 x 1 5/16 w/o washers (will likely use 3/8-16 x 1 1/2” w/hardened flat washers)



25. Bell housing Inspection Cover: 4@ 1/4-20 x 5/8 hex hd. bolts w/o washers. (due to odd ball length: I used 1/4-20 x 3/4 w/hardened flatwashers and star lockwashers).

26. Transmission to Bell Housing bolts, 4 @1/2-13 x 1 3/4 w/flat washer. 27. Lower shifter seal/boot and stainless screws

28. Transmission Rubber Mount to Exhaust hanger bracket Bolt set: 2@ 7/16-24 x 1.25“ ( or 1 1/2”).

29. Transmission Hanger Bracket/Rubber Mount to transmission ** Bolt set (metric): 2@ M10-1.50 x 35 mm Hex head Cap Screw

30. 7 @ 5/16 x 3/4 Hex Hd bolts for Muncie shifter plate
31. 3 @ 3/8-16 x 3/4 “ “ “ “ arms. (or use 3/8 x 1” w/Flatwashers & Lockwashers)

32. Transmission to Bell Housing bolts, 4 @1/2-13 x 1 3/4 w/flat washer.
33. Starter bolts: 2@ 3/8-16 x 4” (and/or 3/8-16 x 3 1/2”).

34. slip yoke for 1 3/8” diameter, 32 tooth spline output shaft.
35. Hurst Shifter w/mount bracket & linkage

36. Hurst stick (has 3/8-16 thread for knob & a locking nut)
37. Hurst 4 speed shifter knob (3/8-16 female thread)

38. 4 speed shifter plate to mount on console
39. Speedometer cable gear fitting retainer (1957-81)

40. Speedometer cable gear fitting in transmission (4 spd) 1965-75
41. Speedometer cable gear fitting seal, 11/16” (1965-82)

42. 1971 Muncie, M-20 4-speed transmission. 43. Driveshaft w/ujoints installed. C-clips2@ 5/16-24 x 1 1/2” hex hd. bol

----------------------------------------------

WILL NOT USE/replace: Clutch safety switch & rod (neutral safety switch). Vehicle Speed Sensor (ACDelco # 213-196 for manual)?

COULDN’T FIND..YET Harness to connect the back-up light switch to the plug connector in the center console.

FYI: Grade 8 bolts can take more Torque Ft/Lbs. than Grade 5, but make allowances for lubrication (10% less) & mating material (alum?). I use Gr. 8’s mainly because they will stretch less over time than Gr. 5 with the same torque applied.

Manual drive shaft, longer than the Automatic Drive shaft by <1/4” Larger U-joint on Transmission end and smaller U-joint on Differential end. (Automatic has same (smaller) u-joint on both ends)

The Manual shaft has about 1/2 to 3/4” play after installation
..manual transmission crossmember , (bolt up, not welded)
{anticipating removing old crossmember for easier tranny removal}
4@ 3/8-16 x 1 1/2 & 2@ 3/8-16 x 4” + 2 nuts.

( ‘81 Assembly Manual shows same crossmember for auto & 4 speed transmissions)
(There are many clutch “brand Names” but only about 5 or 6 mfgs..ZF Sachs, Exedy, Valeo, Perfection, Luk, Perfection most are IMPORTS )

** Caution: Item #24 , an odd-ball metric bolt, may have been a SAE “American” size originally such as 3/8-16 and was tapped to a larger size. Also, beware of the “softer” casing this is going into; don’t strip!

[kunneman]

Originally Posted by like2drive

Hope this helps someone...TRANSMISSION EXCHANGE PARTS LIST

This thread is a gold mine from my "newbie" perspective. Many thanks.

I had a new crate 350 HO with headers installed by a shop in Atlanta, and I just added true duals without cats (NE tags). It'll be a while until I can swap out the automatic for a 4-speed, but I've got a copy of the parts list already tucked away. Thanks again.