Gearbox ID 1948 TC

[bergxu]

Hi gents,

Wondering if there’s an easy way to determine if I have a TC or TD gearbox in my car. The engine was replaced a long time ago with a TD unit (engine # 27379) but I’m not sure if the gearbox was as well and I’d like to change the gear oil in it but don’t know if I should get SAE140 or SAE90, since it’ll depend on which box is in my car. I can say the gearbox casing is painted green, so I’ll assume it’s still a TC box but want to be certain before ordering oil. Thanks in advance for any assistance!

[cdrolshagen]

Hi Boy,
on a TC box the remote is fitted on the top/middle of the casing,
the remote on a TD box is fitted on the rear end of the box - rear cover,
cheers Carl

[bergxu]

Thanks Carl!

[Steve Simmons]

I've never seen a TD box in a TC so I don't know what the easiest way to figure it out is. I think the dipstick on the TD box is a wire loop handle, whereas the TC has a chrome MG octagon handle. If you look down the hole in the gearbox cover where the filler cap is, the TC cap is threaded into the rounded aluminum cover. The TD has its filler plug threaded into a flat steel plate. If you get underneath then the differences become very obvious. Here are a couple photos I pulled off the web.

[bergxu]

Thanks Steve, I’ve got the car on my lift so got underneath to have a glance, looks as though it’s the proper TC ‘box.

[Tom Lange, MGT Repair]

TC gearboxes are MUCH stronger than TD/TF boxes, such that racers in the 50's would install TC boxes in their racing TD's. I've never heard of a single TD box installed in a TC; that would be a step backwards.

Tom Lange
MGT Repair

[bergxu]

Thanks Tom, good to know!

[Duncan M]

Foaming of the oil can be a problem in these gearboxes that call for 140W. I started out running GL4 140W from a major supplier, and one day I checked it after a drive and the dipstick only registered foam. Switched to a multi-weight and have never had foam again.

Now I run the straight GL4 140W only in the BC steering box and the differential. The scroll seals on the axle ends work best with straight 140W, though the original pinion scroll cap never leaked with any of the oils I have tried.

[bergxu]

I’ve ordered four liters of Dynolite “Mild EP” which is an SAE 140 gear oil, I was going to ask if something like Red Line MTL would work in a TC box but everywhere I looked/read, it was a pretty unanimous 140 weight is the way to go, so your experience is interesting to hear

[Steve Simmons]

MTL will work, but the best product Redline makes for the job is 75W-140-NS. They specifically recommend it for the TC gearbox. I've been running it in two TCs and an SA with good results.

[Duncan M]

Run your Dynolite 140 through the differential, and change it often. The oil in the diff of the TC never heats up much over 130F, and it is always dirty when I change it out after 2500 miles.

The transmission oil stays pretty clean. All the Redline oils are "yellow metal safe." I use the 75W140NS in the transmission, also.

[bergxu]

Interesting, thanks gents. I’ll keep the Dynolite for the rear axle and will order up some Red Line 75/140NS for the box.

I run Red Line gear oils in just about all of my other classics, so am no stranger to their product. Always good quality.

[bergxu]

P.S.

And the gearbox basically holds 1 US qt, which is what I see as 1.5 imp pints. Just want to be sure!