Saturday, October 18, 2008
In attendance were ten club members and one visitor asking to become a new member. Weather was sunny and warm enough to leave the door open. The host supplied coffee on the warmer and soft drinks on ice. Someone else brought bagels and cream cheese and a large box of hot coffee. Apparently coffee was the preferred drink of the day as only a few sodas were consumed.
Most of the day was spent rebuilding complete George Goeppner's MGA late 1500/1600-type gearbox. On start of disassembly it was obvious that someone had been in there before. The first clue was a nylon replacement type bushing on the remote selector lever in place of the original split bronze bushing. Next clue was missing thrust shims for the input ball bearing. There were no signs of any fragments of the missing thrust shims inside the box, immediately applying the term DPO (or DPM) to the prior mechanic.
We replaced the typical worn parts, 2nd gear synchronizer ring and layshaft. The laygear rear needle bearing was losing its original needles on disassembly. This is a weak point in these units anyway, so we shortened the bearing spacer and installed two replacement type 11-roller cartridge bearings in place of the original single 18-roller rear needle bearing (no longer available), converting the 3-bearing layshaft into a 4-bearing unit. The front two original 18-roller bearings were in good condition, so those were retained in preference to the replacement type 11-roller parts.
The oil sump was quite dirty with more dirt in the oil passages. This is not nice but is common when the gearbox oil has not been changed for a very long time. The mainshaft spigot bearing oil supply orifice was clogged, starving the spigot bearing for oil. One of the spigot bearing rollers was broken, so we replaced the whole 18-roller set along with cleaning out all of the oil passages and the entire housing. The input ball bearing had a broken retainer, so we replaced the input bearing with a good used one from the spare bits bin.
The gearbox rear mount (a big silentbloc bushing) was previously removed, so installing a new one was easy enough. Just position the rear housing on its side over the pipe of a round tube jack stand, select a large wrench socket to match the OD of the steel shelled rubber mount, and tap it into place with a heavy hammer.
Careful measurement with a depth micrometer revealed the need for 0.018-inch stack of thrust shims inside the front cover for the input bearing outer race. This is an unusually thick shim stack, but it is within the high end of normal manufacturing tolerance buildup.
Final assembly with new gaskets and seals was finished
about 6-hours from start, allowing plenty of time for show and tell and lots of personal interest. Everyone present now understands the working of synchronizers, shift selectors, lockouts and detents, and is also likely qualified (and emboldened enough) to rebuild an MG gearbox without assistance. The only thing not covered was replacement of the rear mainshaft bushing for the early and mid 1500 type gearbox, as later units use a ball bearing at the rear.
Jim Dades brought a MGB 3-synchro box for inspection. Fred Schaffer brought a MGB 4-synchro mainshaft for inspection (maybe needing nothing). Both left when the first gearbox was just finishing up about 3pm. I reckon they learned enough to know to be able to fix their own parts. Steve Boswick has been through a complete gearbox rebuild before and is a close friend and near neighbor to Jim Dades. That might eventually lead to another gearbox tech session.
Tim McGowan brought a Midget 1500 gearbox (Triumph Spitfire top loader type). After everyone else left we opened it up for inspection. It looked good inside, so we replaced gaskets, rear seal, speedometer pinion seal, and the clutch release ball bearing. It was a busy day, and no one was taking pictures, but there are lots of pictures of the parts and process available on the club web site from past tech sessions. See web links below for more information on the MG gearbox.
- Barney Gaylord
A Call from the Past
An interesting email came across the club website and to Barney’s attention about an MG in the Chicago area (well, maybe still in the area). I have attached the message below, if this is your car, or you know about it, please contact Barney (firstname.lastname@example.org) for the email address and information from the former owner.
Comments: IN 1976 I SOLD MY WHITE MGBGT TO SOMEONE IN CHICAGOLAND AREA. I STILL HAVE THE ORIGINAL SALES PAPERWORK FROM THE PLACE IN ICELAND I BOUGHT IT FROM. CURRENT OWNER MAY BE INTERESTED IN HAVING RECORDS. THE SERIAL NUMBER WAS 3401.262063