Big service: what would you change preemptively?

when those are brass test them and see if ok, if iron then change

test how much AMP they need and if not too much and makes no noise no need to change. also those you can change with the engine in the car

so here what I change when the engine is out:
all seals ( camshafts, cranshaft )
replace the water and oil hoses with silicone hoses
then of course the timing belts with tensioner bearings and of course the other V-belts
I think I have not to mention the valve cover gaskets when adjusting the valve clearance

think over the diff

 

All the rubber fuel and vapor hoses on the tanks and the fuel return hoses to the engine. Get a look at the fuel filler hoses too. The coolant hoses all over the firewall connecting all the pipes and radiators and the coolant hoses at top front of engine. If it is a version with air injection I replace the check valves. Like Joe said, consider the differential. Replace the shifter bushing and the shift shaft seal.

 

since long time some other members and also me say:

it is not a question of IF the diff housing will break, it is only a question of WHEN

please use the search function and you will find a lot of info about those broken diffs

 

Alex, I don't know how you define "big service" or if you are doing this work yourself. A few additional service/replacement items come to mind, some of which are not engine-out dependent. However, doing so during engine-out could make you or your mechanic happier. EDoug

1) The front wheel bearings are not sealed and the grease evaporates away.
2) Heater inlet and return hoses routed through the tunnel. (Not sure if Brian was including those above or not.)
3) AC control vacuum line routed through the small tunnel channel from the vacuum reservoir.
4) Brake booster vacuum hose routed through the rocker panel area.
5) Brake caliper hoses

QUOTE: "What do you mean with the last sentence ("think over the diff")?" As an input, for owners that have had their TR from new or essentially new and have NEVER subjected their car to abuse such as hole-shots, burnouts and the like, the confidence level of diff integrity will be higher than most. At least that is how I have always treated my 1986 Testarossa and view near-term diff integrity.

 

The differential carrier had a flawed construction technique and they were weak. Very late in 512 production they were fixed. Paul Newman here sells a good copy of the no longer available part. If he has none available Modena Engineering in Australia make another choice.

If you wait for it to break it can destroy the ring and pinion, it will destroy the left side housing and possibly the spider and side gears.

 

Try a search using "diff carrier" in this Boxers/TR/M section -- you'll only get 194 prior threads to read with many gruesome pictures. It's a weld in the stock 2-piece diff carrier that can fatigue fracture and break, but when it does, many other parts can be damaged. The aftermarket replacement diff carrier is a 1-piece billet part with no weld.

 

Seems a minor thing, but make sure that the acc cable gets well re-lubricated from the engine end -- very difficult to do with the engine in the car.

 

Alex, a couple more items:

1) Starter solenoid problems: Brian made recommendations to use a 1/4 inch spade connector to fix the weak feed-thru connection for this heavy solenoid load in the large C12 (?) connector under the coolant expansion tank. Many choose to add a relay instead, but Brian's simple addition of a spade connector seems to address the problem. I chose to parallel the original connection with the spade connector to be proactive. Tons of stuff on this to search here.

2) Look at your brake fluid reservoir and it's hose that feeds the supply to the adjacent clutch master cylinder. Feel this supply hose to see if it feels wet or if it has turned to a tan color. If either, the hose needs replacing, or maybe just do it.

EDoug