need driveshaft ideas, advice, help

[pbcanney]

I am part way through the conversion of my 81 from automatic to 4 speed. I got the 79 BW installed this weekend and have run into a bit of a snafu.

For reasons only Chevy would know, the 81 automatic uses smaller, lighter duty universal joints than the beefier manual trans Corvettes.

So after I installed the trans, and cross member, it's then that I realized the 81 driveshaft would not bolt up to the 79 front trans yoke.

So as I see it I have these choices:

1. replace the driveshaft with an earlier heavier duty manual trans version (as well as the differential yoke)​
2. have the front universal holder cut off and replaced with an appropriate larger one​
3. find a lighter duty front yoke that fits both the trans and the current drive shaft​
4. locate one single universal joint that's a mixed breed (te easiest solution, but does this half breed universal even exist?)​

Also, when I went to remove the rear differential yoke from the input shaft of the differential, I found that a 1 1/16th socket is too small and a 1 1/8th is too big. wtf.. :confused​

Its been a long day..... any response or advise at all would be helpful.​

 

[black_81_vette]

I would have to say your going to need the driveshaft from a vette that had a four speed. Truthfully that would be the easy route.

 

[bossvette]

I would have to say your going to need the driveshaft from a vette that had a four speed. Truthfully that would be the easy route.

thats the easiest route with Carlisle a week away it should be just a 400 mile drive away

FYI there are "conversion" u-joints available I used one on my Yellow Truck try summit racing parts you will need to know the dimensions of the u-joints you are matching up.

 

[pbcanney]

Thanks. I'm doing both.

I have a conversion U Joint on the way from Summit while I hunt down a drive shaft

 

[like2drive]

been there , done that. hope this helps

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. Z bar (bellcrank)
16. Clutch Disc, 11” (1 1/8“ Dia.-26 spline input shaft)(10120997)
17. Pressure Plate, 11”; (GM 15638389, get Corvette!not BOP)
Pressure Plate to Flywheel bolts, 6@ 3/8-16 x 1” , Grade 8,
Hex Head w/shoulder to prevent movement.
18. Throwout Bearing (GM 15680264); use the shorter (~1.25“), not
the longer (~1.75”)
19. Pilot bearing (roller type)
20. Alignment tool (26 spline)
21. Flywheel (3991469), 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. Torque 55-60 ft./lbs.
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-clips, 2@ 5/16-24 x 1 1/2” hex hd. bol
44. Speedometer Pencil Gear
----------------------------------------------
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 the 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 for auto & 4 speed transmissions)

(There are many clutch “brand Names” but only about 5 or 6 mfgs..ZF Sachs, Exedy, Valeo, Perfection, Luk, 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!
PROM for manual tranny: 519K 8108 1008 6630 CK1911 or
GM # 1225434 (get at Standard Blue Streak)
Speedometer Pencil Gear.