Spitfire 1975 Spitfire 1500 shifting problems when hot

[wmeans8776]

Ive spent the past 2 years working on a 1975 Spitfire I saved from the scrap yard. I actually saved a 1974 at the same time, but It’s still waiting it’s turn…

Anyway, I went through the overdrive tranny and it actually wasn’t too bad. Cutting a long story short, the tranny is back in, I’ve put about 25 miles on the car and it has been shifting perfectly through all gears around the neighborhood…

but wait, there’s more…

I decided to go a little further to the local fuel station (about 5 miles) and everything was fine on the way there. However, after getting fuel and jumping back on the road, it wouldn’t shift into second and was very hard into first and third . I just wanted to get it home, so just milked it. after getting into the garage and letting the car cool, it shifts fine again…

I did install a new exhaust which runs straight down the middle of the car and is tucked up in so it’s as high as possible and doesn’t hang down. I wonder if that exhaust is getting the tranny too hot and causing the shifting problems.

Thoughts? Seen anything like this before?

 

[bobhustead]

Maybe getting the clutch hydraulics too hot?
Bob

 

[Trevor Triumph]

When you say hard... Is there gnashing of teeth? What about hot but engine not running? When was the clutch hydraulic fluid changed and bled?
T.T.

 

[wmeans8776]

When you say hard... Is there gnashing of teeth? What about hot but engine not running? When was the clutch hydraulic fluid changed and bled?

All new hydraulics (slave, master and line). Engine is running at normal temps. After a little more playing , it definitely only happens after everything gets good and hot. I pulled the trsnny cover and the trsnny itself is getting pretty hot.

I got some exhaust wrap and am going to pull it and wrap it to see what happens.

 

[charlie74]

What kind of fluid did you use in the transmission? I had difficulty shifting my TR6 OD transmission after trying 30 weight non-detergent oil in it. After I switched back to gear oil (yellow metal friendly GL-4) the transmission was back to normal…

 

[Andrew Mace]

First thing I'd check is the oil level in the gearbox. Also, I'm curious: Did you get to try the overdrive? If so, did it engage and disengage ok?

 

[wmeans8776]

First thing I'd check is the oil level in the gearbox. Also, I'm curious: Did you get to try the overdrive? If so, did it engage and disengage ok?

Good questions. Rebuilt tranny and I’m using 70/80 gear oil filled to the brim (but not overfiull.

the solenoid doesn’t pull overdrive in. It does click mildly, so I think it’s bad…

 

[bobhustead]

If your engine is running on the edge of too hot, stopping the exhaust radiating heat by wrapping it could put the operating temp above where you want it. A barrier that leaves the exhaust exposed but blocks it from the hydraulics could be preferable.
Bob

 

[Bakerman8888]

I’d start with the clutch fluid myself. It sounds like it has absorbed water over time and is boiling off at operating temps, hampering the cylinder motion to engage the fork. Exhaust wrap might help, but ultimately if your clutch fluid is compromised you’re gonna want to address the root before other stuff breaks (like your master or slave piston).

I recently did an overdrive swap-in and used MTL due to the instructions of the gearbox rebuilder calling for a 30W non-detergent type lube. It was quite simply too light for good shifts and overdrive engagement. After about 30-40 miles OD would get ultra sketchy. Switched to MT-90 and it shifts cleaner and OD works like a dream. Oil weight matters, especially in the OD gearbox.

Clean your OD filters if you haven’t. The cover is located in a ridiculous place; 6 bolts drop the OD filter cover which sits directly above the exhaust pipe… you need to at least loosen up part of the exhaust for access.

If your solenoid clicks, that component is probably fine. My first look on the OD issue would be the filters under that cover. This involves draining fluid and dropping part of the exhaust for access again, but is otherwise pretty straight forward. There is a filter behind the cover and another inside a plug behind the cover (no special tool needed to open the plug, just use a needle nose to grip the holes). Check out a part diagram to make sure you’re pulling the plug for the filter, not the pressure relief valve.

It’s also possible there are other things causing OD to be sad, but this is a simple thing to try before giving up on it. Clean the filters in a container of gas, blow them dry, then give it a try. You might be lucky. Mine was getting extra crabby, so when I switched weight I also took the time to check the filters in the OD. Even on a fresh rebuild with about 2k miles there was a lot of crap in them.