I agree it should have changed down or not even changed into 2nd at 20mph – but what does ‘seems to rev slowly’ mean, either it is or it isn’t.
TBH I've never tried to drive an auto with power problems that hasn't simply stalled as soon as you put it in drive, at which point I've fixed the engine problem which er seems to be the obvious thing to do. I'm often surprised by people who go on a long test drive when they have obvious problems - I wouldn't get past the end of the drive. lol
I was just the passenger on the test drive and I described what I heard and observed. The engine never had high revs and leaving the traffic lights at the bottom of the hill and pulling away there was a slow increase in road speed but soon hit the hill and the engine seemed just stuck in too high a gear and struggled up the hill and road speed went down dramatically and the auto box didn't change down on its own so my son had to select first gear manually and floor the pedal to just about manage to crawl up the hill and back home. Even driving on the level, the box seemed to be in too high a gear and we crawled along at 20 to 30mph. I agree with @Zed its not changing down when it should but I will check out the engine at the weekend to make sure that's running its best. Auto box after that.
and thanks @77 Westy for your input regarding auto box not changing down as it should. this may well turn out to be the issue.
I have an auto. I agree with Geoff, reading all the above it sounds like it's stuck in a high gear. These auto boxes are smooth, but you would defo notice if it changed gear. But, for certain, you should be able to easily proved by driving it like manual by using the gear leaver manually through all the gears; just like driving a manual but without a clutch. Sent from my SM-N970F using Tapatalk
Seeing as there are only 3 forward gears it’s fairly obvious which gear you are in. Locking into 1st gear as I said even if the torque converter is locked up once rolling the engine should have enough guts to pull it along nicely & up a hill. Try a test drive on the flat or slightly downhill going from locked in 1st then second then D to see if you have 3 gears/ratio’s. If you have 3 working forward gears I would be looking at a lack of power from the engine first
This was my exact problem when I brought my van. Couldn’t do more than 50 downhill. Got it serviced, gaps checked etc. and one done it was like a rocket in comparison.
Not on my '79, though maybe late late ones on the T25 had this? Mine just works mechanically via the accelerator cable.
i have a bay in my workshop at the minute with an electrical switch under the pedal for kick down, my friends is the same too, 78 I think, I wonder if they just fitted 2 different gearboxes regardless of year
Yes I think they started out with the 030 with the vacuum operating system and electric kickdown then moved on to the 010 which is just cable operated. The troubleshooter guide above says the 010 was introduced in 1976 model year, but there's bound to be some oddities about.
Its a 1980 T25 and I think it has no electrical kickdown switch just cable operated. I am not certain its an 010 box, but I should be able to find the 010 number on the box somewhere. Unfortunately last weekend I didn't check out the cable and operating rods setup from auto stick to box and pedal to box and carbs. I will get under and check it out at the weekend and see what happens when the auto stick is moved and the accelerator pedal is moved and if the carbs butterflies are opening correctly. Maybe its stuck or worn out somewhere in the linkages, I will find out. Apart from looking at diagrams I haven't yet seen it for myself. I will check the engine is running correctly and firing on all 4 and do compressions. Unfortunately (or fortunately) I wasn't driving the van last weekend. But going up the hill from a standing start was a struggle and even manually put in 1st and the pedal to the floor didn't give the expected high revs so it struggled to make it.
Have you checked the infamous splitting/falling off servo pipe boots on the outer sides of the inlet manifolds?
Ok went to see my son today and to have another look at the auto gearbox issues. The engine starts and idles around 1500rpm when hot at stationary. We are not driving it. Adjusted both chokes so they open fully and close when cold to correct gap. With my son in the cab and me underneath, I noted that the auto stick cable moved correctly at the box. However, when my son depressed the accelerator pedal there was a lot of slack until eventually with the pedal near the floor, I noted the lever arm at the auto box started moving but only about 1/2 inch and there was some slack in the carbs operating rod at the box lever. The accelerator cable under the pedal was in my mind rather slack. We had the air cleaner box off and with the pedal to the floor, the carbs throttle butterflies did not open any where near fully open, whether engine off or running. The bendy shaped rod from box to carbs balance bar was firm with spring tension at the carbs, but there is a little movement at the box end. With the engine running my son depressed the pedal which went way down due to the slack and when fully down the engine revs went to about 3000rpm. I had always assumed the carb butterflies should open fully wide at full throttle but we are only getting about 1/4 inch opening. one carb is opening less than the other. The exhaust is black smokey and after a few minutes of idling about 1500 rpm, the engine hunts and dies. My son said the current problem is recent as he had driven the van during late 2021 and early 2022 and the auto box behaved as it should with smooth up and down changes. The only difference since then is he has fitted the interior and new wiring. Fitted a new fuel pump push rod and fitted a fuel filter which it didn't have before. I noted today that the new filter was black rather than clear. We have the nice new tank from the old van and plan to fit that soon along with new filter and lines. So what has changed? Help please.
Does it have a rev counter or are you guessing the revs? 1500 isn’t an idle, about half that is. Both throttle butterflies should open equally and should open fully. In neutral, i.e., no load, and the throttle wide open the engine should rev until valve bounce or a rev limiting rotor arm stops it (or something breaks). Black smoke from the exhaust is a rich mixture. Someone with experience of the auto box will answer but with the throttle pedal near the floor and the lever arm at the auto box starting to move sounds like the kickdown to me.
Re the RPM's we used an Accuspark timing gun which shows engine revs based on 4 stroke setting on the gun, same reading from each plug lead, it may not be accurate and the idle sounds too high to me. The rotor arm has a limiter of 4500 RPM. We did not get a stable idle, on starting the revs were about 1800 which came down to about 850 when the chokes opened up but the revs went up again to around 1500 and the engine started hunting and stopped. Mixture is definitely rich as the exhaust gases, exhaust pipe and plugs are very sooty. Presumably the carbs are starved of air. Also my son said the brakes are needing more pressure which he assumed was a vacuum leak to the booster, but maybe the air flow through the carbs is a possibility, it seems a coincidence to me.
