Wills Engineering LLC

Instruction Manual For Wills Big Car Saginaw Conversion Kit

CLARK’S PN C11431 May 03

Corvairs with midengine V8 conversions have been around since the late 1960s, and are still being built today. Why? Because late model Corvairs (66-69) were among the best-looking cars from the 60s and they handle extremely well, thanks to a suspension copied from the Corvette. The addition of V8 (or V6) power to this lightweight car makes it outperform most of the cars on the road today.

This kit is designed to adapt a big car Saginaw 3 or 4-speed transmission to a 1966 or later Corvair rear end. This transmission is exactly the same length and uses most of the same gears, shafts and bearings as the Corvair Saginaw transmission found in 66-69 Corvairs.

You can pick up a Saginaw transmission with either a wide, close or intermediate ratio spread. These are usually identified by the first gear ratio. The 3.11 first gear transmissions are commonly found in 74-76 Chevy Vegas and are usually in excellent condition after an easy life behind the Vega engine. This is the wide ratio trans and it has the same ratios as a Corvair Saginaw. There is a 2.85 first gear transmission, and a 2.54 close ratio first gear transmission. Saginaws have been available from 1966 to 1987 in a variety of GM cars. They can be identified by three shift levers on the case and none on the tailhousing (3 speeds have two levers). All Saginaws were cast iron.

The above list is not complete. To determine the ratio of the trans you have, put it in 1^st and rotate the output shaft one turn exactly, counting the revolutions the input shaft makes. A little more than 3 turns is a 3.11, a little less than three is a 2.85, and about two and a half is a 2.54. The 2.54 trans will take more abuse since there is less torque multiplication in first gear (the weakest gear) than other transmissions. Some 2.54 input shafts have a radial groove in the spline area, and some 3.11 input shafts have two grooves. No groove is a 2.84 input shaft.

The 3.11 transmission works well with the 3.08 or 3.27:1 differential gear sets. There are 3.08, 3.27, 3.55 and 3.89 differential gear sets available.

If you are converting a Crown conversion over to a Wills kit to take advantage of the stronger connection between bellhousing and transaxle, note that the new transaxle is about ½" longer than the Crown transaxle, due to the thicker adapter plate. You may have to make some adjustments to your rear mount. The new trans will not require supporting at the bellhousing, only the motor mounts and rear support are used.

If you are building a car from scratch, you may want to order the Crown Instructions (Clark’s p/n C5357) before starting, as the Wills kit is just one component of many you will need, and the Crown Corv-8 was a well thought-out kit.

You will need the following at a minimum, besides the Wills Saginaw Transmission Kit, Shift Linkage Kit and Shifter Mount Kit:

Hurst™ Shifter

Subframe (make your own, or use the Crown one, p/n C5356)

Rear transaxle mount (make your own, or use the Crown one, p/n C8707)

Clutch Master Cylinder

Clutch Slave Cylinder

Water Pipes to Radiator

Radiator/Electric Fan

Seats/Engine Cover

Throttle Cable

Headers/mufflers

4-spider gear differential unit

Front Disk Brakes

You will also need an engine. The Crown subframe will accommodate Chevy V8s from a 283 to a 502, but a 350 is recommended as the largest engine you should consider. The Corvair differential is the weakest link. A 4.3 V6 will fit, and with the Wills kit almost any GM V8 will bolt up if you have the bellhousing for it. The subframe will need custom motor mounts to accommodate engines other than Chevys.

A 350 Chevy V8 rated at 350 HP will give 0-60 times of about 5 seconds, and 12.5 to 13 second quarter mile times, due to the light weight of the Corvair (about 2900 lbs. with a 350 engine). Disk brakes are recommended as the stock drums/linings are marginal for high performance use, although metallic or other performance linings will help. For inspiration, visit http://www.v8corvair.com/

Insert the modified mainshaft into the Corvair rear end being used; it should slide into place without sticking and the splines should engage the matching internal splines of the hollow pinion shaft. If there is any play or rattle when rotating the shaft in both directions, then the pinion shaft splines may be excessively worn. It is suggested that the pinion shaft be replaced before proceeding further.

Trial fit the adapter plate to the rear end. One side of the plate is recessed to align to the pinion bearing adjusting sleeve. Install five 7/16-14UNC socket head cap screws finger tight. The sixth bolt, nearest the top right will not fit until the hole in the rear end is slotted about 1/8th inch. After observing how the hole must be slotted, remove the adapter plate and using a rat-tail file or rotary burr make the slot. Trial fit and check; repeat until all six bolts can be inserted and tightened finger-tight. The plate should fit flush with the rear end. Remove once more and set aside - you are now ready to work on the transmission.

Tools needed: RTV sealant, good transmission snap ring pliers. A Corvair shop manual will help.

Drain the transmission. Remove bolts holding the side cover and pry off. If shaft forks fall out, retrieve and set aside with cover. Remove bolts holding the clutch gear bearing retainer and pry off. Remove the snap ring retaining the front bearing to the input shaft, and then with a screwdriver, pry gently under the locating ring on the bearing, preventing the input shaft from moving forward until the bearing slides forward and off the shaft.

Remove the five bolts holding the tailhousing to the transmission case and pry back. As the tailhousing and mainshaft move back, move the input shaft back at the same time. The whole assembly can be removed through the rear opening in the case. If the input shaft separates from the mainshaft, all the needle bearings will fall into the case and will have to be retrieved. You may have to slide the 4th gear synchro sleeve forward for clearance as you remove the assembly.

Pull the input shaft off the mainshaft, catching the needle bearings and 4th synchronizer blocker ring. Set aside. Spread the rear bearing locating snap ring with snap ring pliers, and slide the tailhousing off the mainshaft. The rear bearing, gears and synchro hubs can now be removed as follows:

Remove snap ring from one end of the mainshaft. Press off the synchronizer, third speed blocker ring and third gear. If you don’t have access to a press, try this method. Set a block of wood on the floor and cover with a shop rag. Holding the assembly vertical, raise it 2-4" above the block and rap sharply down on the block. Repeat until the parts are jarred free. Set parts aside, remove next snap ring and repeat until the shaft is bare. Clean all parts in non-flammable cleaner and inspect. Now is the time to replace any worn parts, such as blocker rings (same as Corvair). Do not dissemble the synchro hubs. You do not have to remove the counter shaft gear assembly unless the gears are damaged.

The Saginaw case needs to be modified by drilling two holes to let transmission fluid flow to the rear end and vice versa. Place the adapter plate on the case and hold with three cap screws. Note that there is a 0.75" diameter hole in the plate right above the bottom bolt hole. Use a scribe to mark the hole outline on the case, then remove the plate, centerpunch and carefully drill a 0.625" diameter hole through the case inside the scribed line. Be careful as the drill breaks through not to damage anything inside the case. Clean out any chips or metal filings. This 5/8 inch hole will line up with the one in the rear end.

Secondly, there is also a 0.50" diameter hole in the plate to the left of the top right bolt hole. Use a scribe to mark the hole outline on the case, then remove the plate, centerpunch and carefully drill a 0.50" diameter hole through the case inside the scribed line. Be careful as the drill breaks through not to damage anything inside the case. Clean out any chips or metal filings. This 1/2 inch hole will line up with the one in the rear end (see drawing 2).

Run a bottoming 7/16-14 tap into the transmission case holes to ensure that the mounting bolts don’t bottom out before the adapter plate is fully seated against the transmission.

Assemble clean parts onto the modified mainshaft in reverse order of disassembly. The order is:

Input side: 3rd gear, blocker ring, 3rd/4th synchro with shift fork slot towards shaft middle, snap ring. Rotate blocker ring to notches to align with synchro keys.

Output side: 2nd gear, blocker ring, 1st/2nd synchro with shift fork slot towards shaft middle, snap ring. Rotate blocker ring to notches to align with synchro keys. Next blocker ring, 1st gear, flat washer, spring (wavy) washer. Don’t install snap ring yet.

Using a little wheel bearing grease wiped around the inside of the input shaft cavity, install the needle bearings (fourteen) into the input shaft. The grease will hold them in place. Make sure that the 4th gear blocker ring is in place, then carefully install the input shaft onto the end of the mainshaft without dislodging the needle bearings. If you do dislodge one, the transmission will not go together.

Slide the rear bearing into the adapter plate and gently tap in. With the flat side down, bearing retainer up the bearing retainer groove will be at the top (see drawing 3). Spread the retaining ring, and tap the bearing gently through until the retaining ring seats in the groove. It may help to cool the bearing in the freezer and heat the retainer in a 250 deg F oven for a few minutes first. Bolt the retainer to the adapter plate using four #8-32 socket head screws provided. Slide the plate onto the mainshaft, bearing adapter end first. Using a soft drift, tap the bearing/adapter plate onto the shaft. Make sure that the flat and wavy washers are in place.

CAUTION! When tapping the bearing in, use a piece of tubing slid over the shaft, or a soft drift and tap only on the inner hub of the bearing, never on the outer ring or the adapter plate. When the bearing seats, install the snap ring. Do not re-use any snap ring that does not grip the shaft tightly. They should not be free to rotate.

Smear RTV thinly onto the case to seal to the adapter place. Now, install the mainshaft, input shaft and adapter plate assembly through the rear opening in the case. You may have to slide the 4th gear synchro sleeve forward to clear as you install the assembly.

Slide the input shaft bearing onto the input shaft and install the snap ring. Install the clutch gear bearing retainer and gasket and torque the bolts to 20 ft-lbs. If the mainshaft slides back more than about ½" the needle bearings may fall out, and you will have to start all over, so keep the mainshaft from moving backwards. Install the five 7/16-14UNC socket head cap screws and torque to 45 ft-lbs (let the RTV set up for ten minutes before tightening). The mainshaft and input shaft should spin freely and independently when the transmission is in neutral (all synchro rings in their center positions, not locked to gears).

To install the side cover, the transmission must be in neutral, reverse idler gear must not be engaged, i.e. it must be slid towards the adapter plate. Line up the shift forks, (the trimmed one is the 1st/2nd

fork and is trimmed so it doesn’t hit the reverse idler gear), and slide them into the synchro sleeves as you install the cover. The shift mechanism must be in neutral.

CAUTION! Be very careful of the reverse shift fork - if you move it the wrong way the reverse detent ball and spring will fly out with high velocity and could cause injury. Wear eye protection. It’s tough to reinstall, too. Use a new gasket here, too, and install the bolts and make sure the cover is not hanging up but sits flush to the case. Torque to 20 ft-lbs. Check that all gears can be selected by operating the shift levers.

Run a bottoming 7/16-14 tap into the rear end case holes to ensure that the mounting bolts don’t bottom out before the adapter plate is fully seated against it.

Using a new gasket (Corvair) or RTV, slide the transmission shaft into the rear end. The adapter plate should locate into the rear end snugly centering the shaft. Install six 7/16-14UNC bolts and torque evenly to 45 ft-lbs. Note that three bolts are shorter (1.25" long) to thread into the adapter. Make sure these do not bottom out against the transmission case. The three longer (1.50" long) bolts thread into the differential case. Fill transaxle to proper level with the correct type of hypoid gear lubricant (posi or non-posi).

The Corvair Saginaw transaxle as installed in Crown cars is shifted by a push-pull-twist linkage similar to the stock Corvair. To allow the use of a Hurst™ Competition Plus or Indy shifter you must use a big car Saginaw side cover in place of the Corvair side cover. If you are using a Saginaw transmission with an adapter to the Corvair or Speedway rear end, skip down to the fourth paragraph.

First, make sure the trans is in Neutral by pushing the (push-pull) shift rod in all the way, then pulling it out to the first detent position. Remove the cover, then remove the gear select lever which is attached by one bolt to the push-pull rod in the bottom of the transmission case. These parts are not needed. Leave the push-pull rod in the transmission case, or you will have a fluid leak.

With the trans still in Neutral, and the Big Car side cover/shifting forks also in Neutral, put the cover in place, making sure the forks seat in the synchro grooves and the Reverse finger seats in the Reverse gear groove. Use a new gasket, and do not install the two lower bolts on the side cover at this time. Test the operation of the side cover by operating the shift levers. Some transmissions may need the shift forks to be moved further into the synchro grooves to get proper engagement by adding a thin washer between the shift fork and the side cover. All gears should be obtainable, and it should not be possible to engage 3^rd or 4^th gear only when the 1^st /2^nd lever is in Neutral, and vice versa. Note that Reverse can be engaged only when the 1^st/2^nd lever is in Neutral, but Reverse can be engaged at the same time as 3^rd/4^th! This will lock up the transmission and is why a good aftermarket shifter such as the Hurst™ is recommended. Stock shifters were notorious for selecting Reverse and third at the same time due to sloppy linkage with disastrous results.

Put the Wills shift linkage in place, and secure with two bolts thru the side cover. Check that the trans is in Neutral. Remove the stock 3^rd/4^th lever by removing the 3/8 bolt with a 9/16" box end wrench, after bending the locking tabs on the washer away from the bolt head first. Bolt the new 3^rd/4^th lever on pointing forward and horizontal. Repeat for 1^st/2^nd lever, then Reverse. The Reverse lever will point down and backwards at a 45° angle. . All three levers at the bottom of the Wills unit will point vertically down in Neutral. You may need to adjust the lengths of the connecting links to achieve this. See Drawing 4.

This kit is designed to mount a Hurst™ shifter (new or used) to the floor of a late-model (65-69) Corvair in the stock shifter location.

Bolt the LH and RH brackets to the shifter. Note that the clearance notch must be on the passenger side (RH) for the shifter to operate properly. Place the shifter into position, with the shifter arms protruding into the tunnel, and note that your water pipes may need to be moved slightly for clearance. You may have to open up the hole in the floor slightly for proper fit. Drill through the four mounting holes with a 3/8: bit, and bolt the assembly in place using the supplied 3/8 bolts and nuts.

Check to make sure the shift knob feels comfortable when you are sitting in the driver’s seat. Some Hurst™ shifters have short, vertical sticks that may be too far forward. Do not shim the front of the brackets to tilt the stick backwards and move the knob back, or you will not be able to engage all four gears!. Hurst™ made a variety of sticks, the best being one which is about 11-12" long, and angles back similar to the Corvair stick.

To connect the shifter levers to the Wills shift linkage you will need three lengths of 3/8" Schedule 80, black, galvanized or stainless steel pipe, about 6 feet long. Cut the heads off six 3/8-24UNF grade 8 bolts 4" long, and insert three of them ¼" into one end of each pipe and weld. These thread into the shifter buttons that connect to the shifter arms. The other three are welded to the other ends after they are bent. Insert a short length of 5/16" diameter steel rod through the shifter frame notches and all three shift arms to hold them in the Neutral position. With the three pipes connected to the arms, note that the shift rods will need to jog to the driver’s side about 2" after exiting from the tunnel to clear the engine oil pan. Starting with the rod nearest the driver, mark the rod about 26" from the shifter. Remove it and bend in a vice at 15 degrees, then move about 8-10" more and then bend back at 15 degrees to give a 2" offset. Re-install and check to see that the rod will line up just to the inside of the 3^rd/4^th lever. The supplied rod end will attach it to the lever. Mark the next rod (1^st/2^nd) at about 26" from the shifter, and bend similarly. This rod should line up just to the inside of the 1^st/2^nd lever. Finally, the last rod (Reverse) will run almost straight back under the oil pan, then angle up. Remove it and bend in a vice at about 15 degrees, about 8" from the reverse lever. Re-install and check to see that the rod will line up just to the inside of the Reverse lever, and not hit the oil pan as it is shifted. Thread the last three headless bolts ¾" into the three rod ends on the shift levers, and then mark the pipes where you will need to cut them. Remove the rods and weld the bolts to the pipes. Re-install one last time with jam nuts and tighten them against the rod ends once the lengths are set (See drawing 1).

Remove the 5/16" rod to allow the shifter to be operated. Try shifting into all four gears. See the http://www.mrgasket.com/ web site for hints on adjusting the shifter for optimum operation. Note that Saginaws don’t shift well when the car is not moving, especially into first and reverse.

Wills Engineering LLC 650-368-5201

cjwills@msn.com