The V8 Owners Forum -

Hello esteemed forum members.
I would like to replace the slushbox in my 1972 P6 restoration project with an LT77 speed manual. I understand that there were many different versions of this gearbox. Which would be most suitable for my car? I have the wider auto tunnel, so there'll be enough room for a manual box, albeit less room for the clutch pedal. Other than a manual pedal assembly, what will I need? I'm thinking gearbox, bellhousing, shift lever, rubber gaitor, tunnel cover (the plastic bit from the centre console to the back ashtray), clutch, flywheel, release bearing; what else is required that I've overlooked?
Furthermore, what is a reasonable sum of money to pay for a used box, without a guarantee, (i.e: off the bay or similar), and what would I have to pay for a rebuilt/reconditioned box from a reputable company with a guarantee? Any recommendations for gearbox suppliers?
Your input is most welcome, oh wise forum members!

Hello Al,

You will also need a point fabricated to attach the rear of the box onto the underside, along with suitable modifications to the tailshaft, longer or shorter, or a new complete tailshaft altogether.

Speedo connections are another area to consider.

I don't have a manual box in my P6B, so I may well have missed some other areas too.

Ron.

Al,

You dont say where your based, it's helpful when advising peiple where to look for parts.

Lokk for someone breaking a SD! the later the better and get the LT77 and possibly the propshaft so you can have that modified to the correct length.

You will need to modify as Ron said the gearbox crossmember with mounts for the LT77, and you will need the pedal assembly form a manual P6 and a flywheel and clutch for a SD1

I would suggest that any LT77 that has not had a rebuild will need a little attention, synchro's and bearings would be the norm, they are pretty tough boxes and replace the bushes on the remote and where the remote is bolted to the gearbox itself.

Do you know what final drive ratio you have as they are usually higher on cars that originally did not have a fifth/ overdrive gear.

Kevin.

You can use the standard P6B automatic propshaft.

All P6B's have the same 3.08:1 diff ratio. You could fit the 2200 diff (3.54:1) for improved accelleration at the expense of outright top speed and some loss of economy.

Early SD1 LT77 gearboxes have a 0.82:1 (Or very close from memory) later ones upped it to 0.792:1. (Once again from memory.) fifth gear.

The box fits easily into the smaller manual tunnel, and the gearlever comes up in exactly the right place. No gearbox mods are required.

I did the conversion on a 3500S in the mid 1980's and after a few owners the car is now back with me.

I swapped my BW35 for the LT77 and used the auto bellhousing with an adapter plate and some machining to fit the release arm out the side and a mount for the slave.
Propshaft was the original auto.
Some fiddling with the rear mount, but not serious.
I took my pedal box/mount out and custom fitted the clutch and brake pedals to suit me, to good result.
Not too painful a job and very satisfactory. Be sure that the "new" box is in good nick or the input bearing will fail like mine did.......resulting in a 4spd O/D Jag box..... soon to be replaced with a Toyota Cressida T21.

You'd think I would learn my lesson sometime...... Nah!