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TR4/4A TR4A OD Follow Up

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KVH

KVH

Obi Wan
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Well, it's running good and for 3 weeks that operating shaft hasn't slipped in the pinch bolt. I think that trick of widening the gap with a file and re-pinching worked. I hope.

Here's a question. The Moss book and my manual show rubber washer-shaped magnets under the metal screen in that huge drain plug for the OD. Moss says it's a set of three.

Are you supposed to use all three, or do you "guestimate" the play and use just one, two or three depending upon clearance? Three seems a bit tight, but I'm curious.

It's a Laycock de Normanville Type A (or something like that).

Thanks.
 
AFAIK, all 3 on the later OD with the notches around the plug. The screen will crush a bit to make room for them.

The early units with the hex flats on the plug did not have magnets originally, but I added 1 or 2 magnets anyway. Wasn't room for all 3 with the early plug tho.
 
This is because of the achillies heal of the A type OD.It is a tiny one way valve that lets oil into the accumulater well. If any swarf,grit,dirt,or other unk crud get stuck in the valve, will leak back to the pump and never build up the 400 psi the unit needs to engage. Its a bitch to clean so if you have a good A type,take good care of it(fresh oil,magnets,fresh flowers and candy)Do not give the oil to your spouse,nor put flowers in the OD.....
MD(mad dog)
 
Tore down my old unit a few weeks back that was in continual use from 74 to 96, but was slipping at the end. It had sat since (read back surgery). I'm sorry I didn't take some photos. The swarf/shavings were incredible and packed in every nook and cranny, hi and lo, even though I tried to be religious about 10k oil changes. No magnets in my mine, and maybe the reason for the nasty scratches in the accumulator bore (and unfortunately on the rings also). Not sure what I can do there. The other very bad discovery was the effect of the sulfur containing oil used last (even though it was drained) on all the brass and bronze in box. all that stuff will have to go. Under magnification, very bad pitting. And will probably have to put in another brake ring and lining. And lastly if you're cleaning it, pull that access plug near the business end of the accumulator, that hole was really loaded.
 
TRTEL said:
maybe the reason for the nasty scratches in the accumulator bore (and unfortunately on the rings also). Not sure what I can do there.
Click to expand...

If you can find a good machinist, it is possible to bore and sleeve the accumulator. I don't think Herman does them any more, but maybe John Esposito does.

Another alternative is to convert to the IRS setup, which uses a sleeve inside the original accumulator bore and a smaller piston.
 
FYI, my OD operating shaft and pinch bolt setup is still working after re-tightening the bolt and monkeying a bit with the split in that operating lever--I've had to redo this setup 3 times already.

I'm taking a trip soon. So, let's say my OD operating shaft slips again while I'm out of town.

I'll have to just forget it and stay in 4th, but I'm noticing that the car really doesn't want to run at more than 2900 RPMs, and that's slow for a traveling speed.

Do you folks go 3000 and higher RPMs steady on the highway without OD?

[Side note: In 1972 I drove my first TR4 to Mexico going 85 and 90 most of the way. No OD. For some reason it didn't bother me back then]
 
KVH said:
Do you folks go 3000 and higher RPMs steady on the highway without OD?
Click to expand...

I routinely drive over 3000 rpm even with OD :driving:
 
I often cruise in the TR3A (no OD) at something north of 3K. That particular engine has always been very smooth at higher RPMs -- I just had to get over the notion that this was abuse and accept that (if everything is working well) this is a good RPM range for these engines.

I think some TRs pick up a buzzy vibration around 2800 RPM that goes away a bit above that. Anyone else heard or experienced this?

KVH said:
...In 1972 I drove my first TR4 to Mexico going 85 and 90 most of the way. No OD. For some reason it didn't bother me back then
Click to expand...

I did a lot of things in 1972 that didn't bother me at the time. Fortunately, the statute of limitations has run out.
 
Geo Hahn said:
I think some TRs pick up a buzzy vibration around 2800 RPM that goes away a bit above that. Anyone else heard or experienced this?
Click to expand...

Was that why they fitted that monster weight at the back of the transmission on later TR4A's (not sure if the TR4 ever had it)?

Scott
 
HerronScott said:
Was that why they fitted that monster weight at the back of the transmission on later TR4A's (not sure if the TR4 ever had it)?
Click to expand...
I believe so. At least some TR4s had it, as there was one on the TR4 I bought for it's OD many years ago.

Some cars also had a reinforcing strap from the rear mount to the gearshift extension; and there is a service note about sliding a length of heater hose over the shift lever to reduce buzzing.
 
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