Need some Turbo 400 transmission help
 

The car is a 74 Grandville. It seems sloppy going into gear and when you hit the gas it seems slip just a tad. The other symptom is when I was driving it earlier it seems to take while going into 3rd gear and when you let off the gas at like 50 and get back on it... again just a slight slip. The trans fluid and filter has been in there probably 30 years. So heres what I did, I obviously checked the fluid not a bright perfect red red but OK and it does not smell burnt. Checked vacuum hoses at the trans and carb, at the carb is 4 years old and fine, on the trans connected and no rips or tears. I also had the old lady in the car and the column shifter jiggles a bit and you can move at the trans too. The column rod jiggles at the trans too. Maybe a simple adjustment of this? Its rusted where the rod goes through the horizontal rod to the trans and subframe so I kroiled the crap out of it. Anyone else have any ideas? Thank you!

Replace the filter, top off the fluid, see any diff.

Also be sure the HP is good so a weak engine isn't the issue. Set Total ADV to 34* (vac adv hose off during that) around 2500 rpm.

OK! I'll change it this weekend. Does the fluid actually lose its uummmpphh?

Not really. I ran the 1/4 mile in a car i bought with a fully cooked TH400, and it shifted firmly. Some clutch packs were fried to the metal. Probably had a low-fluid situation before me.

an old trick guys do for worn out sloppy shifting transmissions is to use type F fluid or something like b&m trick shift which ive read is just mostly type f. i had a higher mile th400 that had a sloppy 3 gear shift under load behind a 455, changed the fluid to type F and it made a noticeable difference, kept that trans in the car with lots of abuse for 10+ years.

need to exchange out as much as possible, not just a pan drain & fill like when you change the filter. i do a fluid exchange buy unhooking the return cooling line at the radiator, start the engine with the end of the hose in a bucket and let the running engine pump out about 2 qts, shut off engine & refill with 2 new qts then repeat until you either see new red fluid coming out or youve done about what the system holds.

i cant say if fluid looses its "uumph" but it can definitely wear out, most vehicles call for a trans fluid change at some interval, modern cars are usually around 60-80k, even with the modern so called "lifetime" ATF.

if new fluid doesnt help, its time for a rebuild or new trans.

When you drop the pan, see what debris is there. It sounds like overhaul time to me.

At a minimum the direct clutch pack is going South on you.

Since it's been at least 30 years since it's had any attention simply time for a rebuild, so I'd start there.

Dropping pans and pissing with snake oil is just prolonging the agony........IMHO........

type f is definitely not "snake oil"... firmed up my 3rd gear shift very good & kept the car on the road for many years as a broke teenager & into my mid 20's. that car saw more abuse than most on here & the trans kept up with it for longer than it should have.

i agree if its going bad a rebuild is ultimately needed, but for many transmissions depending on how bad the shifts are it can prolong the life for quite awhile to get you by until a rebuild can be done.

It is a hard decision to rebuild the trans in this car. I bought the car for $2500 5 years ago and its a daily driver and very rusty at this point. But then again I do love it. Itll cost $2000 to rebuild probably. If type F works I'll try it.

should be able to do a basic rebuild on a th400 for much cheaper than $2000 assuming you or someone you know can remove it from the car. heck a new TCI, summit/jegs/monster/etc brand th400 is cheaper than that and they are considered "heavy duty". call around your town or near by bigger towns for some estimates.

i can't guarantee the type F will fix your issue but based on what ive read & heard for decades as well as my personal experience it should definitely help a slightly mushy shift to buy you some time or possibly last a very long time, if the clutches are totally shot then fluid probably wont help. just be sure you replace as much as possible, not just 2-3 qts from a pan drain & fill. the exchange process i mentioned works good & wont cause any damage if done 2 qts at a time.

good luck!

Thanks, its worth a shot. Yeah your right, I could just look for a used transmission too.

Well... it worked! I don't think the pan was ever off this transmission. I got about almost 2 gallons out. I put in 7.5 qts of type F and sent it. it now shifts fine, the car only has 80k on it so I think it was never changed since 1974!!

Good to hear that snake oil helped this issue, just as countless others have said for many years. now just keep your fingers crossed that it keeps shifting ok.

As mentioned, if the trans/clutches are bad no fluid will fix that, but if its just a mild sloppy shift type F & other performance ATF's are supposed to firm up the shifts pretty good. the type F in my higher mile abused th400 made a noticeable improvement.

If the fluid was really that old then using fresh dexron3 type probably would have improved the shift too. was the filter dirty or pan showing signs of sludgy crap on the bottom?

i forget the actual capacity of th400's but its more than 2 gallons, i think its more like 12-13qts, would be a good idea to pump out another 4qts in 500 miles or asap to get more type F in there.

Plan to change the filter to be a metal screen filter in about 300 miles. You will thank me later.