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Identify a LT77 gearbox??

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lebochet9
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Identify a LT77 gearbox??

Postby lebochet9 » 31 Dec 2007 16:20

Just finished pulling the 5 speed gearbox out of my car, and guess what...there is no serial number on the casing. Where my "Spare" box (now in pieces) has a serial number telling my its a C-suffix box, this one has got nothing, not even the cast land next to the drain plug where the serial number shoud be. Otherwise, it looks identical. So what does that mean then???
Thanks (and have a good night [;)])

1980 DHC TR7-V8 (was an 8V, then a Sprint)
Back on the road after 3 years restoring...

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Postby Workshop Help » 31 Dec 2007 17:24

Try looking at the underside rim at the front of the gearbox. The number is probaly there. Our gearbox does not have the pedastile cast for the number stamping. It is a 'B' box, which indicates it was built during early production, and the number is stamped there on the underside rim.

If you do have an early gearbox, you are lucky. You input shaft is priced by Victoria British at about $100.00, versus about $270.00 for the later 'C' and up units. Please note, an early gearbox differs principally by having a smaller bearing than the later 'C' unit supporting the input shaft. This makes practically no difference for use on a 4-cylinder engine.

As for the laygear, observe that tho Victoria British specifies their's is for the later 'C' units, it will fit the earlier boxes with no modification.

Mildred Hargis

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Postby john 215 » 01 Jan 2008 12:48

Hi
This is the info i have:-
14ACL Speke built car 5 speed (TR7)
CL Canely/Speke built car (TR7)
15A TR8
G16A SD1 2000 (poss 4 speed)
G17A SD1 2300/2600
G19A SD1 3500 VP/SE
G22A SD1 3500 Police Spec
G23A SD1 2600 Police Spec
G26A SD1 2400 Diesal
G27A SD1 2000 5 speed
G28A SD1 Vitesse
G30A Sherpa range of vans
May help in the quest to ID?
Cheers John.

LIVE LIFE A QUARTER OF A MILE AT A TIME!
1979 3.5 FHC(STATUS PENDING!!)
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lebochet9
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Postby lebochet9 » 06 Jan 2008 16:14

Ok. Thanks for the advice. The box in the V8 had the serial number on the underside: 19A02432A. The other box that was in the TR7 when I bought it was CL085215C. So, according to the info from John, the V8 box was originally from an SD1 3.5 VP/SE and the TR7 box was probably an original TR7 box. (The car was a 1980 Canley model)

Now the questions:
1) Are the ratios the same in the 2 boxes?
2) Is an A suffix box going to be weaker/stronger than a C suffix box?
3) Any other differences between them?

Basically the decision I have to make is either to rebuild the C Suffix box, which is in good condition, but needs bearings and an oil pump or to strip down the A suffix box, try to find and cure the oil leak, and the stiff selection problems.

Thanks - Laurence

1980 DHC TR7-V8 (was an 8V, then a Sprint)
Back on the road after 3 years restoring...

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Postby john 215 » 06 Jan 2008 18:06

Hi,
Not sure about the ratio's but the top gear between post and pre 1981 model year (Sept 1980) cars is different.
These guys are experts on the LT77 and R380 boxes,they have been featured in a '4x4 is Born' on Discovery rebuilding the box in that vech,might be worth dropping them a email-
http://www.ashcroft-transmissions.co.uk/index.html
Will try to find my BL training book on LT77 to see if that mentions ratio's.I would say the 'A' is probaly a weaker box than the 'C' as these boxes had developments as far as bearings ect during prodution
Cheers john.

LIVE LIFE A QUARTER OF A MILE AT A TIME!
1979 3.5 FHC(STATUS PENDING!!)
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1982 2.0 DHC Soon to be a 4.6 fire breather!!
Read My Blog http://www.waringstowntr7s.co.uk/blogs/ ... hp/John215

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Postby Workshop Help » 06 Jan 2008 22:14

Mr Laurence,

If I may, the internal ratios are the same on the TR7 gearboxes regardless of the end letter, A-C, except for the late fuel injected cars that had a different 5th gear that allowed an 800rpm drop from 4th versus the 550rpm drop from 4th on the earlier TR7 gearboxes.

As for basic strength, there is none as they all have the same basic gear case, inner plate, rear extension, main shaft, synchros & hubs, and main shaft gears. The difference is the later 'C's have a somewhat larger input shaft taper roller bearing and the laygear has some minor modifications over the production span of the TR7. But, the late laygear will fit just fine in an early case.

The change to a larger input shaft bearing caused a minor change in the gear case as the front hole was enlarged to fit the larger bearing and the input shaft was also changed for that bearing. Overall, both early and late gearboxes are equally strong.

Given the choice, we opted for the early 'B' gearbox for the TR7 as the input shaft, front bearing, and shims were less expensive than the late 'C' gearbox. Since our engine is relatively stock, the 300hp capacity rating of the LT77 gearbox rendered useless the argument for going with the late 'C' gearbox with it's larger front bearing and any imagined benefit it may have offered.

May I suggest, on tear down, please examine the condition of the teeth on the input shaft and the corresponding teeth on the front gear of the laygear. If striations are present on the input shaft teeth along with a longitudinal groove on the teeth of the laygear, these two parts should be replaced. Therein will be the determining economic factor on which gearbox should be overhauled. In our case, we saved the early gearbox as parts prices were less.

The choice is yours.

Mildred Hargis

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Postby bmcecosse » 06 Jan 2008 22:29

Mildred - if I may ask - what oil should I use in the LT77 gearbox ? Book says EP80 but many say ATF is better - but what viscosity of ATF should I use - there seem to be various!!

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Postby Workshop Help » 07 Jan 2008 01:24

In answer to your question, it would seem to be a matter of personal tastes. We prefer to use the high-mileage formula ATF at about $2.00/qt from the local Walmart because we will be changing it at every engine oil change. Others choose the more expensive MTF's or Manual Transmission Fluid from GM or Pennsoil or Red Line. Then there is the synthetic crowd. The one thing that appears to be in common agreement is EP80 gear oil as the factory specified should be avoided.

However, this argument can be turned on it's head if the local climate is tropical year round. Consider, once EP80 is warmed, it thins out. In a tropical climate, this thinning out period would be very short if at all. Thus, EP80 would flow easily and be well suited for a LT77 application. Do you reside in a tropical climate? Are you anywhere near the earth's equator? Since we aren't, we use an ATF as it flows easier in cold winter weather.

For those in tropical climates, perhaps you might enlighten us with your gearbox oil experiences? Is your initial shifting experience baulky or must you drive a while to warm up the gearbox fluid and then shift easier using a standard gear oil?

Mildred Hargis

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Postby Hasbeen » 07 Jan 2008 02:18

I am in Queensland, Oz, so a reasonably hot climate.

I am using AFT, because I found that with EP80 I could not get
second at all, [except when stationary] for at least the first
3 miles. I would then still have some difficulty with second for a
further 3, or 4 miles. All 4 of my 7s have been the same.

This was the case even in summer, when the minimum temperature is
likely to be above 20 degrees C.

Hasbeen

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Postby Workshop Help » 07 Jan 2008 02:31

There we have it, from that fine gentleman speaking from experience. EP80 is not the gearbox oil to use, even in hot weather. ATF it is.

Which particular fluid remains your choice. There are simply too many opinions and preferences out there to single out which is best.

Mildred Hargis

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Postby Launie » 07 Jan 2008 03:27

Mildred, excuse me for being off topic, and feel free to respond in a separate thread, (or not at all of course), but I've been following your posts lately, looked back at your earlier posts, and I am amazed at your detailed knowledge! I've been wanting to ask, and can no longer resist...What is your background, if you don't mind the question? Is it not unusual for a 72 year-old woman to be stripping down a TR7 gearbox? Again, my apologies if I am being too personal or off topic.

I thoroughly enjoy your wonderfully detailed posts, and your demeanor (which definitely comes across). I can see you are a great asset to this forum.

Respectfully,

Launie
'76 TR7 FHC
'86 Renault Alliance (daily driver)
'77 Chev Silverado
'86 BMW 635CSi

Hasbeen
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Postby Hasbeen » 07 Jan 2008 05:43

Yes please Mildred, where did this encyclopedic knowledge of things
Triumph come from.

What knowledge I have is all very recent.

About 8 years ago, the first thing I did with my first 7, when I got
it home, was change all the fluids.

After driving it about 200 yards, & making quite a few phone calls,
the second thing I did to it, was drain the new gearbox oil & refill
it with AFT.

Hasbeen

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Postby john 215 » 07 Jan 2008 18:40

Hi Mildred,
You certainly know your gearbox's [:D] Been looking for a lady that strip and rebuild a LT 77 all my life!! That link for that SD1 site you posted before is great.As Launie said you are a asset to us all.
Cheers john


LIVE LIFE A QUARTER OF A MILE AT A TIME!
1979 3.5 FHC(STATUS PENDING!!)
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1982 2.0 DHC Soon to be a 4.6 fire breather!!
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Postby FI Spyder » 08 Jan 2008 06:25

For sure Mildred, don't leave us.

My Spider had regular gear oil in it when I picked it up near Sacramento, the temp was high eighties to low nineties. It was too hot to put the top down as the sun would burn you. We Canadians laugh at Californians with A/C in their convertibles but I now understood why. You have top down driving for three seasons and summer is not one of them. The car would shift fine into second even at six in the morning when I would hit the road (for the next two days.) The third day in Blaine, WA the weather had turned and I woke up to cool cloudy skies and threatening rain. I ran into my first expeience with baulky second gear.

I found that when cold you had to rev it up to about 3 grand then give a positive shift into second. When I changed to Pennzoil synthetic it was much better.

A club member had synthetic in it and when having it serviced the mechanic changed the oil to ATF saying the oil in there was too "thin". He could no longer shift into second when cold. He's going to change it back to synthetic this spring.

TR7 Spider - 1978 Spifire - 1976 Spitfire - 1988 Tercel 4X4 - Kali on Integra - 1991 Integra
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Postby bmcecosse » 08 Jan 2008 19:19

Mildred et al - thanks for the 'Poll' that ATF is the way to go - however, here in Scotland (very much NOT tropical!) the makes of fluid you suggest are not available - but various viscosity of ATF are available - so can I ask which viscosity I should go for ? Car only used in 'summer - ha!' when temp between 5 and 20 C very rarely!

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