Dif drain & speedo gears

[sirfixalot]

How is the LSD oil drained from the diff?
Have just put turbo 700 auto in my car diff is 3.55 ratio with  265  x 15 " tyres any one have any info on what  speedo gears will suit
to get correct speedo reading

[Cameron 77C3]

Don't know about other vettes but on a 77 there is no diff drain.  You have to remove the old oil through the filler hole with a plunger.

There is a thread on speedo gears here somewhere.  I'll go find it for ya and report back shortly

Cam

[Cameron 77C3]

Ok I found this

hi cam the formula is
63360 X axle ratio
-----------------------[divided by]
3141.6 X tyre diameter in inches
the figure you get for that is then times by 8. This gives ya the number of teeth needed on the speedo driven gear.


And this was in this thread, CLICK ME

Hope this helps

Cam

[Chromie]

Hi sirfixalot ;42
It is recomended that you remove your differential. then remove the cover flush out all the old oil.
Install a suitable drain plug and reassemble
make sure that you use correct differential oil ;27

[77CVT]

TH700 with 3.55 gears!!!   Man that will have some hook off the line!!

;46;46

[sirfixalot]

Ok how do i make / fit a drain plug to diff?Dont mind removing cover plate not real keen to remove diff as still have to fit exhaust, tailshaft, carpet & seats & sort gear box before going to Queensland

[Chromie]

Originally posted by sirfixalot
Ok how do i make / fit a drain plug to diff?Dont mind removing cover plate not real keen to remove diff as still have to fit exhaust, tailshaft, carpet & seats & sort gear box before going to Queensland

Hi sirfixalot;42
You don't have to remove the differential (it is only recomended);27
What you need to do is drill a hole in the differential half way between the front differential mount and the rear camber strut mount on the differential.
You will be using a 350 chev engine oil gallery plug so the thread size is 1/4" NPT and the drill size is 7/16"
make sure that the drain plug only goes in so it is flush with the inside surface.
This will enable you to fully drain all the differential oil out (allow 24 hours for draining with the vehicle level)
then you simply refill the differential with fresh oil
I use Penrite 85W-140 limited slip gear oil it comes in a 2.5 litre bottle and you will use about 2 litres.:spook
Hope this helps:luv

[Chromie]

On another note i am unsure if the TH700 has the same speedo gears as;53 the TH350
If it does I have a full range of speedo gears in stock;43

[jdunne]

sirfixalot,is that correct for your tyre size?it is usually 255.60.15 which is standard......there are two different coloured plastic gears one driving and the other driven...most of the vendors sell them and you just need the right combo...i purchased mine from Bowtie overdrives but i'm sure vendors here sell them....i think mine was 17/42 combo...the 700r4 was a holden box in vn commodore so gmh probably have them...john;35