Triumph Repair: Overdrive Transmission, pilot bearings, starter solenoid

Question
QUESTION: I am planning on replacing my 1969 MK3 non-synchro 1st transmission that is mounted to a 1971 (FK1682HE) MK4 engine. If I put a complete Overdrive Transmission in it does it have to be any certain kind or do I just need to be sure it fits a MK3 and 4 and then make the driveshaft and mounting changes.

Thanks,
Tod

ANSWER: Hi Tod,

The only important difference between the transmissions used on MGB were the type of starter motor and Bendix. The early "B" used a long nosed starter motor with a Bendix that went all the way through the bell housing and when the starter was activated by a remote solenoid it sent the Bendix gear from the rear towards the front to engage the flywheel. The later models used a starter motor with the starter solenoid mounted directly on the starter motor. This Bendix gear was moved toward the rear to engage the flywheel and had a short nose on it and thus the bell housing only had a hump in that area but no hole. One of the starter mounting bolts was also located in a different position so even though the two different types of transmissions could be switched, it took a lot of work and cutting to get them to mate up. Also there ware two different size pilot bearings needed to make the switch.

If you have both transmissions out all you need to do is look at the section of the bell housing where the starter motor goes and if that part is the same, they can be switched, over drive or no overdrive. The fit or no fit has nothing to do with the overdrive, it is the bell housing and pilot bearing that determines if it is a simple bolt in fit.

I have installed a late model OD transmission in a older "B" that had the long starter without the solenoid mounted on it. but it required cutting a large hole in the bell housing and cutting a corner off of the bell housing to clear the body and doing some modifications to the starter mounting bolts.

The over drive transmissions are highly prized units by MG owners.

Howard

---------- FOLLOW-UP ----------

QUESTION: Sorry Howard but this is a Triumph and not an MGB.

Answer
Sorry about that Tod, I guess I am answering these questions far too late at night. I looked back and you did say Triumph and a Mk3 and Mk4 and a prefix of "FK", which indicates it is a Spitfire.

But the same is true about the pilot bearing and the bell housing bolt pattern except as I remember the spitfires had the same starter mounting on the 69 and 71.

The gearboxes were the same on most of the Triumphs between the OD version and the non-OD versions. The only thing you need to do it count the number of bell housing bolts and note their positions and measure the input shaft to confirm they match which I think all the Spitfires were the same.

I don't remember if there was any difference in the tunnel cover or not between the Two so look at it for clearance too.

You will need to add a switch to operate the solenoid on the OD and wire it up. You also might want to add in a relay to take the load off of the switch you add. It would not hurt to put a condenser on the wire too as coils tend to have a charge built up when operating and when you turn them off they can cause a small spark in a switch or relay and burn the contacts in time. Without knowing the value of the needed condenser you should be able to use any condenser from a pointed ignition system.

Howard