Differential Mounting and Lotus Documentation

[CBUEB1771]

I got very curious about the proper mounting of the differential in the "S1 Progress Report" thread in the Elan Gallery section. Curious because I am starting to build up a new chassis for my +2 and wanted to get this correct. I didn't want Gary to accuse me of moving too far off topic so I am starting a new thread here. The intended orientation of the bolts is shown in the attached scan from the Elan +2 Workshop Manual (1974 edition, Section R, page 4). The same orientation is shown in my 1970 edition of the Elan Workshop Manual. Lotus documentation is frustrating as ever because parts discussed in the workshop manual don't appear in the service parts list and vice versa. With respect to installing the differential the workshop manual states:

"Lift the differential unit into position from the left-hand side and adjust unit to give a clearance between the top of the unit and and the chassis crossmember. This may necessitate the removal of one of the two washers on either or both sides. A minimum of one washer must be left between the top lugs of the differential unit and the chassis cross member and between the head of the bolt and the rubber bushings. It is essential that the large 2 in. (5 cm.) diameter washers are used and not substituted by others, as they serve a twofold purpose in being both spacers and stopping the rubber bushes from spreading. Harder differential mounting rubbers (Part No. A36 R 6000) were introduced at Chassis No. 50/1550. New bolts (Part No. 50 R 027) which secure the differential to the mountings were introduced at Chassis No. 50/1880. Two washers (part No. 26 R 003) are now fitted between the differential and its mounting rubbers, this change being incorporated into current Production from Chassis No. 50/1645."

The same text appears in the Elan Workshop Manual. I don't know how you can create clearance between the diff housing and the chassis crossmember by removing washers. The text also indicates that at one time the bolts were installed with the head at the top. Gary indicates that the bolt orientation was changed at some point. Apparently the drawings and text were never made consistent. The differential stiffening bracket (A036 R 0033) made it into the Service Parts List but never discussed in the Workshop Manual. Therefore we don't know how the washer arrangement changes when using the stiffening bracket. Oh well, I guess I'll follow Figure 3 and use my best judgement on the number and location of washers.

[ppnelan]

I don't know how you can create clearance between the diff housing and the chassis crossmember by removing washers.

Hmmmm... I see what you mean! From memory, I found that it was the BOTTOM of the diff that comes close to the centre channel of the chassis, rather than clearance to the top cross member that is the problem. Clearance here CAN be increased by removing washers as the manual suggests.

Matthew

[crannyr]

Russ.
In the section of my shop manual titled Overhaul, there is detail of the diff install that calls for 3/32" min to 5/32" max clearance between the top of the unit and the bottom of the crossmember (ideal 1/8"). if you use the stiffing bracket a max of one washer or none is required as the bracket substitutes for a washer.
As to the mounting bolt, it wants to be head down. This is to allow removal of the diff in the +2 without removing the gas tank.
hope this helps

Rick