FireballXL5

So... My 81 vette is 'new to me' as of about a month and a half ago... Which had a new 383/TH350 combo dropped in it prior to me getting it... If the seller who I bought it from is accurate in telling me it's only had 254 miles since rebuild( and I tend to agree based on the cleanliness of all those parts(headers hadn't even blued)), new rims & tires, and new exhaust... Then I've now got ~2,400 miles total on all the above mentioned parts...

All was going well, until last Friday... Mind you, this is basically my daily driver, so it's not seeing track/strip time(yet)... But I do tend to play with the first two gears a lot ... Anyways... All of a sudden , from a on ramp to the freeway, it wouldn't shift into third at about 55-60mph... Let off the throttle, and she kicked down into third, then gave it a light touch of gas, and she revved out about 1,000-1,500 Rpms before going into second and getting back up to speed...

So, manually downshift into second, and she grabs like a champ, put her into Drive, and she will only shift at zero throttle... Give her any gas , and she revs out, grabs second, and takes off! But there is no grab in third gear... Unless she's cold. When she's cold, all gears shift fine , 1-2 and 2-3, and she's got low end torque at the pedal in third gear ... When she warms up... Third gear goes away , and she won't shift out of second under load, and won't hold third under load but reverts back to second.

Replaced all the vacuum modulator lines, as well as the modulator itself... I thought it fixed the problem, but it only gave me 10 minutes of glory til she warmed up again... So... Now I wanna try to check the governor, then drop the pan and check filter/fluid... Fluid is nice and rosy, with a tinge of blackish residue on top... Or so it looked like in my catch basin when I changed the modulator...

Had a trans shop look at it/go for a ride with me... They say the trans fluid smells ok on the dipstick, but we didn't have enough time to drop the pan... So I'm thinking I'm gonna do that myself, and look for anything out of place...

It's possible that something could be gummed up/sticking, because according to the previous owner, he only drove it 254 miles in 2.25 years... So... I'm crossing my fingers, willing to entertain ideas, and hoping to provide you guys with some good news when I fix it without a complete overhaul!

If an overhaul is imminent ... I'm debating on; A) rebuilding this current trans ... B) buying a direct swap in TH350 replacement... C) upgrading to a TH400 and being done with it ... D) installing something with an overdrive.

Build specs on the motor are 441hp, but I have no idea what it is actually at... It's got all kinds of goodies on the engine, and stainless headers and 2.5" exhaust all the way back. Now that I've got ~2400 miles on the motor, I figure I can start tuning for performance and get her on a dyno...

I'll start rippin into the trans pan tomorrow morning... Wonder what I'll find?!? Oh btw... Rear gears are still the stock 2.72 or 2.73's this year came with... It's a late 1980 build(oct) with 1981 licensing... Kind of a split year for parts etc... Found that out when I recently replaced some rear u-joints... It's got the rear end of a 80 not a 81...

oldalaskaman

upgrade to 700r4/2oo4R

FireballXL5

I have heard/read that... I guess it depends on what actually went wrong... I did just get/buy the car.. Was hoping not to double my investment right off the bat... Lol. But I do want it reliable, and street friendly... I planned for tis to be my work commuter in all weather except ice...

I'm hoping that it's 'all of a sudden' loss of 3rd gear is a component issue... And not a slipping band... But we will know more when I tear it all apart... Every gear and shift works great, except 2-3 shift/3rd gear hold when hot... All other gears and shifts still work great when hot... Even the downshift... Thinking its governor, 2-3 shift valves, or... Something else internally blocked... Hard to say.. There do seem to be lots of common forum posts about this particular issue, with numerous 'fixes'... Be it a seal, spring , valve body, or governor... Let's hope mine is something similar and simple... ;-)

jnealg

I am rough on xmissions, there are many gravestones in the xmission graveyard due to me. so I feel your pain.

If I ever put a new one in mine it'll be with an O/D

FireballXL5

Brought it to another trans shop for another opinion... After talking with him, think I'm gonna pull it and see what we can find..

The fact that the 1-2 shift is good/perfect eliminates the possibility of a governor issue because it controls both shifts... And the fact that it will shift into 3rd when cold, just won't hold when hot pretty much eliminates the 2-3 shift valve... So.. It's gotta get pulled, and torn down to inspect seals and bands...

Being as it's soo new, I might be able to salvage many parts, and just upgrade/change a few things... Gonna give this one a rebuild at least once, before tossing it aside for another trans... If it goes out again later, I'll know it is just not the right trans for the application. Everyone says the fluid looks/smells good... But I won't know fully til I drain it and inspect the pan/filter...

I'll keep you guys posted as I get the time to work on it... And what the final determination is once inspected/ pulled apart.

tektrans

Upgrading to a 400 isnt neccessary as th350's if built right can take a beating.
I was running 9 second 1/4 miles with my old car with a stout th350.

vairxpert

Could it be overheating badly? As in an issue with the lines going into the radiator or an external cooler (if installed)?

To me, freshly rebuilt with less than XXX miles is an automatic deal breaker when I'm looking at any vehicle. So many out there with claims of less than 800 to even never driven. I think problem car or someone trying to do a flip as cheaply as possible. When it's running perfectly with 10,000 miles, it's out of the woods and good to go, imo.

mikejpss

Did you adjust the TV cable at the carb ? Make sure you try that before you pull the xmission.

FireballXL5

I don't think it was an overheating issue... Because it was a 'all of a sudden' loss of third gear holding power... A month and a half of trouble free driving, then this issue manifested .

Pure speculation here... But if the prior owner only drove it 254 miles since the motor/trans/exhaust upgrades (which I do believe simply on the quality/shiney newness of all those parts) there is one work repair receipt that leads me to believe he may have slipped the clutches(and sold it soo cheap)...

7 months after the engine/trans install, he brought it to a trans shop to fix a leak at the speedo cable... And also did a complete trans fluid/filter flush... Why would he flush the system and new filter with less than 254 supposed miles... Unless he ran her low on fluid (from the leak) and slipped the third gear clutches... Then afterwards hoped to band aid the issue by replacing fluid and filter...

That's all speculation on my part... And the seller did disclose that I may need to upgrade the trans at some point per recommendation of his trans guy... It held for 2,200 miles for me, and I was just starting to put my foot in it a little bit more often (thinking I had sufficiently broken in the new engine by this point)...

So my guess... Is that I'm going to need to do a th350 rebuild, doing the R&R myself... And will still have gotten a great price on the rig as a whole... It may turn out to be a faulty seal or stuck valve body only, and I'll get away even cheaper... But I'm planning on a proper rebuild so I won't be surprised...

FireballXL5

Yea, I did adjust the tv cable, and tried pulling it off completely for a quick run with the same results... I'll be delightfully surprised if it turns out to be something simple... But the only way to truly tell will be to pull it... I don't mind, I like wrenching!

FireballXL5

A few pictures I took before I began disassembly...













There's a dent in one of the pipes... I'll get it replaced while it's out and easy...



So far, only had time this morning to get it up on jacks, pull the exhaust, pull the inspection plate, and pull the rear driveline...

I did talk to the guy who originally built the trans, and while it is out of warranty by time, he is willing to make it worth my time to bring it to him... He's curious what failed , wants to make a good product to stand behind it, and says he will rebuild it for cost plus $50-100 for his time... He's also saying that's its rough to build a trans with a properly adjusted shift kit mated to a 2.73 rear end... But he can/will rebuild it specifically to the other components in my vette... Might go that route...

AGVI

Also do not call your Vette 'she' or use the word 'champ'.

Thanks. Les

FireballXL5

Guilty... Lol. Referred to 'her' as a 'she' in my first post...

What's your reasoning behind this? Just curious...

lvmyvt76

Put headers on instead of replacing the pipe!

David Mc

Those are really bad assumptions. The governor has two sets of weights. One does the 1-2 shift the other 2-3.

The iron valve body bolted to the aluminum case causes distortions due to different rates of expansion. So yes, spool valves sticking can be caused by heat.

Third gear shares the same clutch with reverse. Does reverse work well?

At your power levels the weaknesses in the TH350 start showing up. Input shaft breaking out of the forward drum, intermediate sprag and race failure.

But I think you have wear in the governor or it's bore.

7T1vette

The governor doesn't 'manage' individual shifts; it just regulates governor pressure according to the output rpm. The "two sets of weights" just help it regulate that pressure in a linear manner better. Individual shifts are controlled by the shift valves and the throttle valve system.

vairxpert

It has headers.

FireballXL5

Good point on the bad assumptions... Transmissions were never my Forté, and I haven't owned a true hot rod in over 10 years... So I've been outta the game for a while... And even then, I'd do the R&R, but still let a shop do my trans work... Maybe next time I'll tackle the job myself..

I'm thinking/ it's looking like clutches/bands... The fluid I collected when I changed the modulator, I transferred into a white jug... And it looks pretty dark... It's hard to say how it was treated by the other owner... But either way, the trans is still coming out and getting looked at/rebuilt... Heading back out now to continue pulling it... I'll check the rest of the fluid, see what's in the pan etc... I've gotta work later, so we will see how far I get... I'll post pics of progress as I go...

FireballXL5

Look what I found! Lol. Go figure... Wonder what it's from...

FireballXL5

So, it was a bolt out of the valve body... Not sure if it would have caused my issue... But there is a little bit of metallic flake in the bottom of the pan... No big pieces to speak of... But enough to warrant concern... But I'm assuming anything more than nothing is a need for concern... Right? I haven't torn too far into the removal process... But I'm gonna stop here for today, so I can get some opinions... I would doubt that replacing/ tightening that bolt, and swapping fluid would necessarily cure my issue... Or what kind of long term damage I could cause by those little metallic flakes...