Gearbox fluid ..change?

[Winston]

During my snow and cold bound musings, I was reading my Haynes manual regarding the gearbox. The manual reccomends that the gearbox fluid not be drained unless it's being overhauled and indicates the gearoil, (90wt. I presume),should be "topped off" being careful not to overfill.
I understand the overfill concern.
I am 3rd owner and have not pulled the plug to the gearbox in the three seasons we've been running.
Given the position of the plug I would have to think the only way to check the level is perhaps to use one's finger. Not the most accurate method I can conceive. I'm also concerned about the age and viscosity of the gearoil since I've driven the the TR4a probably 1000 miles by now.
I know I have a clutch slave cylinder to replace, and should do the same with the master, so yes I have noticed a little more difficulty shifting at the end of last season. No noises of any concern and I'm sure the clutch slave will smooth things considerably.
I have been respectfully neglectful to this area of maintenance and would appreciate any and all thought's on the matter.
Oh by the way. I found the clutch slave cylinder I want. Rimmer Bros. Girling part. $114.00 American + shipping. I wonder is it worth the extra cost in a resto mod.

 

[Guest]

Never scrimp on parts that allow you to go and make you stop.

Bill

 

[Winston]

Bill,
The slave could as easily be replaced with a 7/8" bore from Moss and be as safe ,would'nt you think?

 

[vagt6]

Winston, if the TR4 fill plug is on the side of the box, simply fill it until the oil barely begins to leak out. Can needs to be on a level surface. That's how you do it on Spits/Gt6.

A little messy, but accurate!

 

[Hayfever]

Winston: On another note, make sure you get the proper oil. If it is like the TR6 box (I believe it is) you need specifically 90wt GL-4 oil. NOT GL5! GL5 will eat the yellow metal parts inside the tranny (like synchros). You should be able to get Redline MT-90 at a local auto parts store (I know Advance Auto Parts stocks it locally, others can order it). If you don't know what's inside it's probably best to drain it all and refill, you never know if some water has gotten in or something that could cause problems.

 

[Stinky]

The guy that basically rebuilt my car for me when I initially pruchased it, recommended that I change the Gearbox Oil once a year. If nothing else that will help make sure I don't run it low on oil. He said most of the Gearbox problems he sees are due to low oil, or no oil in the gearbox.

Furthermore:

He recommended using Castrol 20w 50 motor oil in the Gearbox. He went on to say that in his years of working on these cars, the gearboxes that ran the Castrol 20w 50 motor oil always looked better on the inside than the gearboxes that were run with GL-4 gear oil.

Of course that's just his observations, and opinion.

But he sure seemed to know these cars inside and out,...so I'm gonna listen to him.

 

[Guest]

I'd like to second hayfever's recommendation of the redline gear oil, also it is a fully synthetic lube. My buddies that run some pretty high horsepower rides have been using redline's products for years and love them. I was having some baulky shifting for awhile using some other standard dino type gear oil (forgot which brand), especially in the cold, and then I switched to the redline. What a difference, butter smooth shifts, even in cold weather. It's a little more expensive but worth every extra penny in my opinion. Funny thing though is that they actually do not recommend the MT-90 gear lube for cold weather street driving, but I think it's been better than the standard dino oil.

I would also recommend changing it if you don't know what's in there and didn't put it there yourself. Cheap insurance.

 

[MGTF1250Dave]

Aloha Winston,

There is a drain plug on the bottom of the gearbox and a filler plug located on the left hand side of the gearbox. The filler plug can be accessed by removing a rubber plug in the transmission cover. With the car on a level surface, oil is topped up until it starts to run out of the gearbox filler hole. This is often more easily said than done.

Since it sounds as if you are uncertain as to quality and type of oil now in the gearbox, I would drain it and refill it with fresh oil. Some manuals will state a 30W non detergent motor oil, while others recommend 90W gear oil. Motor oil and gear oil are rated for viscosity at different temperatures, so both have a similar ability to flow at the same temperature. Personally, I use gear oil since it is engineered for this application.

I find that a hand pump that fits to oil container and a length of clear vinyl tubing works well to add oil to the gearbox. Once the filler plug is removed, you can route the tubing through the transmission cover into the gearbox and pump the oil from the left hand foot well. When you notice oil dripping out of the filler hole your done.

The filler and drain plugs are general iron plumbing plugs, pipe threaded and with a raised square for a wrench to engage. Often these squares have been are rounded over after years of use. I have replaced these with plugs with a counter sunk square. This square is close to either a 3/8 or 1/2 square drive (I can't remember which) for socket wrenches. I found these easier to remove and replace without doing damage to them. Also anti seize or Teflon tape help in future removal.

Safety Fast,
Dave

 

[Simon TR4a]

Hey Winston, pretty comprehensive answer from Dave, I have cut a hole in the (plastic replacement) transmission cover, use a grommet to seal it up, and use a long necked funnel or a flexible tube to fill. I agree that gear oil is formulated for higher film strength (to prevent galling of the gears), I think the sulphur compounds that are added to gear oil are not in motor oil so even if the same thickness its not the same stuff.
I change mine more often than most people as I have overdrive which likes 20/50, but share with the gearbox which likes 90 weight, so I tend to use 20/50 with a little 90 blended in, and hope thats ok. Simon.

 

[Larry4A]

Did a whole frame off rebuild on my 4A except the trani and overdrive, ASSUMED it would be inspected and at the least clean fluid replaced, with all else being taken care of and assembly all done, and driving it for the first spring this last year all went well until the overdrive started slipping, so on a hoist it went , pulled the plug and yuck, no one did tend to it, amazing how these LBC continue to run, advice from this shop guy , who is a MG fanatic was to use ATF first to help flush out the gunk, so we did that ran it for about two weeks, overdrive came back on line, drained it out again, and then put in the proper 90wt fluid. All is well. Draining the trani also allows you to inspect the screen for any metal chunks that may help give advance notice of problems before they occure on the road.
Would recommend a draining if you never have had a look yourself. /ubbthreads/images/graemlins/driving.gif /ubbthreads/images/graemlins/canpatriot.GIF

 

[Geo Hahn]

I also use the RedLine synthetic in the gearbox and it seems just fine. For filling I prefer to run a hose down to the filler hole from inside the engine compartment with the funnel sitting there around the master cylinders (you can just see the filler plug if you peek down there with a light). The stuff flows so slowly thru the small OD tube required that this arrangement makes it easy to fill the funnel and go do something else while it works its way down.

The diff of course has no drain plug, they really thought that was lubed for life I guess. Unless you can suck it out you're left with either topping it up or removing the rear cover to drain.

 

[Guest]

Winston, check with TRF to see if they have the correct part. Sometimes some vendors will sell parts that they say will work but sometimes fall short. As for gearbox oil, the fella that rebuilt my overdrive said that if I used anything but 30wt. non-detergent oil, he would void my warrantee. Had my diff reworked and they tapped a drain plug. Kinda neat. They all leak so as to keep the underside of the car rustfree.

Bill

 

[jsneddon]

I just came across a different opinion about the synthetic transmission oil.... something to think about:

https://www.linkline.com/personal/koblinger/trsc/tech%20articles/translub.htm

One thing about racing; technology is rampant and sometimes we get poor or confusing results. About two years ago, one or two of the current crop of TR racers and a good number of TR owners whose cars are street-driven only began using synthetic gear oils in the gearbox to reduce friction. This did in fact reduce friction by a small but measureable degree, with an equal rise in available power.

Toward the end of last year’s vintage racing season problems began to develop in two particular areas. First, the race drivers noticed that virtually all the TR’s using synthetic gear oil developed a tendency to jump out out of third gear while braking hard downhill. We disassembled a gearbox that had been doing this and found that it could be made to jump out of third gear while performing a simple test out of the car. We held the gearbox vertically in the air and released it, stopping it just short of hitting the ground, at which point it would snap out of third. Making some adjustments on the detent springs and balls in the synchro hub reduced this tendency, but could not completely prevent it. It then became apparent that the combined weights of the shifter shaft, fork and the outer ring of the 3/4 synchro was enough to overcome the resistance of the detent and the ‘box would jump out of gear. We tried changing to a normal gear oil and found that it no longer jumped out of gear.

The second problem with the use of synthetic gear oil came when we noticed that when racing on short, twisting courses where first gear was needed repeatedly, it became increasingly harder to get into first. After about 20-30 engagements, it became progressively more difficult until it could no longer be engaged at all. After we took apart a box that had this problem we found that the synthetic oil was so slick that the heavier gears could not be stopped by the synchro rings. The steel gears were grinding off the pointed teeth until they were flat, preventing engagement. The heavier the gear, the more inertia we had to deal with; first gear is so heavy that its synchro ring failed first.

The cure is to stop using super slick gear oils and change to a standard 80-90 weight gear oil in non-overdrive gearboxes, or 20-50 engine oil (Valvoline Racing is a good brand) in the OD-equipped units.

 

[Alan_Myers]

Hi Winston,

I just noticed your original question about the slave cylinder. It so happens I just bought the correct Girling part for my TR4 from The Roadster Factory for $90.

I believe the later 7/8" bore slave might not be a good idea. I seem to recall there were clutch issues on some of the cars using it. Mainly, the larger bore seemed to allow too little room for proper clutch adjustment, leading to other problems. I'd suggest using the .70" bore, if at all possible.

Alan

 

[Dave Russell]

[ QUOTE ]
I just came across a different opinion about the synthetic transmission oil.... something to think about:

The cure is to stop using super slick gear oils and change to a standard 80-90 weight gear oil in non-overdrive gearboxes, or 20-50 engine oil (Valvoline Racing is a good brand) in the OD-equipped units.

[/ QUOTE ]

Please note that the above references were to Redline MT90 & MTL. A quote from the above link by hayfever:

"Red Line Oil's MTL and MT-90 are designed to provide excellent protection and improved shiftability for manual transmissions and transaxles, having cured the problem of hard shifting in thousands of transmissions with shifting troubles. How? They have the appropriate coefficient of friction for most manual transmission synchronizers (many gear oils, engine oils, and ATFs are too slippery for proper synchro engagement)."

Some oils "may" be too slippery for good synchronizer operation. R/L is not one of them.
D