My new 3:55 Gear did what ??

[cmegga]

It killed my transmission.. thats what.

If anyone followed my last post it was a pretty long discussion on the right gear to put in built up 81. I went with the 3:55, from the origonal 2:81 . I was very please with the results, lots more low end torgue to get up and go !!! I ended up about 3100 rpms at 70 MPh which was ok on the motor, but obvisuly not on the transmission. Anyway I picked it up last night with the new gear and by this afternoon 3 rd gear on my trany was shoot.


My question is should I rebulb my TH 350c traniey or swap to a TH400 or ..how much more is invlolved in going to a 700r4 ?? What else needs to be change and how much more expence ?? What tranie will hold up the best in 3rd gear under high rpms and not break my piggy bank ??

 

[Stallion]

Do you know why exactly it did this to the tranny? And why 3rd gear? Was it because that was the gear you were in with the high RMPs and that speed?

What would cause something like this to happen? :confused

 

[MaineShark]

I've been looking into the overdrive swap. It was looking to roughly be in the $1500 range, depending on options and such. I'd suggest talking with the guys at Bowtie Overdrives (700r4.com).

For the 700-R4, you'll need to replace your torque converter, transmission crossmember, and shifter, and have your driveshaft shortened. If you email Bowtie with the details of your car, and what sort of performance you're planning on, they will reply with a complete list of parts, and prices, tailored to your particular swap.

Joe

 

[cruisin-davey-g]

It killed my transmission.. thats what.

If anyone followed my last post it was a pretty long discussion on the right gear to put in built up 81. I went with the 3:55, from the origonal 2:81 . I was very please with the results, lots more low end torgue to get up and go !!! I ended up about 3100 rpms at 70 MPh which was ok on the motor, but obvisuly not on the transmission. Anyway I picked it up last night with the new gear and by this afternoon 3 rd gear on my trany was shoot.


My question is should I rebulb my TH 350c traniey or swap to a TH400 or ..how much more is invlolved in going to a 700r4 ?? What else needs to be change and how much more expence ?? What tranie will hold up the best in 3rd gear under high rpms and not break my piggy bank ??

cmegga: Wow! Sorry to hear that your trans went. Unfortunately, this can sometimes happen when you go to changing things. Sort of like rebuilding the top end of a motor & not the bottom end. Sounds as if the sprags in the trans were weak to begin with & adding the more gearing in the rear caused it to finally show up. BTW: How is the torque Converter holding up? If you want to go to an overdrive trannie & really don't want to go through all of the mods to put the 700R-4 in. Then I would suggest using the 200-4R trans instead; should be a direct bolt in. And, from what I've been hearing, the 200-4R has a lower first gear & a better third & overdrive gear than the 700-R4. You could also rebuild the TH350 (least inexpensive thing) or go to a TH400 using a real early model one (from the 60's era). Those were the better of the TH400's (have a better 2nd gear with more intermediate sprags & is an overall stronger trans (this is what I've got in mine). So, tell me, did it launch alright?


Dave

 

[MaineShark]

Re: Re: My new 3:55 Gear did what ??

[BIf you want to go to an overdrive trannie & really don't want to go through all of the mods to put the 700R-4 in. Then I would suggest using the 200-4R trans instead; should be a direct bolt in. And, from what I've been hearing, the 200-4R has a lower first gear & a better third & overdrive gear than the 700-R4.[/B]

Tranny ratios:
TH350:
2.52:1 - 1.52:1 - 1:1

200-4R:
2.74:1 - 1.57:1 - 1:1 - 0.67:1

700-R4:
3.06:1 - 1.62:1 - 1:1 - 0.70:1

Multiplying through by the 3.55 rear, for overall ratio:
TH350:
8.95:1 - 5.40:1 - 3.55:1

200-4R:
9.73:1 - 5.57:1 - 3.55:1 - 2.38:1

700-R4:
10.86:1 - 5.75:1 - 3.55:1 - 2.49:1

So, the 700-R4 would work better with the 3.55 gearing currently in the car. The 200-4R would allow a higher-ratio rear (say, 3.90) to be used, while still having a similar overall overdrive ratio. That would give a similar first gear (10.69), and better second (6.12) and third (3.90) gears. But I doubt that cmegga wants to swap his rear gear a second time.

Swapping the rear gear, vs. doing the mods to fit a 700-R4, seems pretty similar in price, although I think the 700-R4 might be a bit cheaper. If cmegga can chime in with what it cost him to have his rear gear swapped, I can give you actual dollar figures of one vs. the other.

Joe

 

[cmegga]

cruisin-davey-g

It launched terrific , I have a 2 mile ride back to work from the mechanics shop, I had it sideways 3 times when I first picked it up. It also felt like it had alot more in the mid range to, at 50 to 60 it took real good. It was definitly the right choice of gear, thanks again for all your feed back with that. If not for you I probably would have went with a 3:36 and not been happy.

I asume I droped 3rd gear just becuase of the operating range, that old tranie wasnt used to countinus driving at 3100 + RPM in third gear with the old 2:81 gear.

With the trannie swap I would like to be around $1200 probably $1500 max , as I broke the bank with all the other goodies this year ( gear, rearsping , shocks, etc ). And this one has VISA written all over it.

Looking at the numbers Maineshark was so kind to post, I think the 200-4R: would be the best fit for me. A higher fist gear then I have now in the TH350 and a decent overdirve. This is probably the one Im going to look for , from what it sounds like I wont have to many other mods as to get it in.

I anyone has a good line an a rebult unit let me know. Im going to check out the guys at Bowtie Overdrives this moring.

Thanks

 

[Yoda]

cmegga,

When you call them ask them how the BLACK 1980 2004R conversion is going

My ole pal BLACKDOG dropped off his CA305~1980 on April 7th for the 2004R conversion. He is hoping to get it back by the middle of May sometime.

They were booked, but since we were on our way back from the Corvette's Against Cancer Phoenix show, we dropped it off, rather than make the trip back down there later.

Best wishes..

Bud

 

[92ghost]

Hi cemmega, thought I would put in my 02 cents worth on your tranny delema. I'd get the TH350 rebuilt with a shift kit etc. and put back in your vette. It should last if you have close to stock power from the engine. This will cost beween $500-$750 if you pull the tranny yourself, and it sounds like you are mechanically inclined. Save up for the 2004R and all necessary parts and take your time doing the swap during the winter. I'm here in Rochester NY and like Syracuse (120 miles apart), winter lasts too long. I doubt you will be driving the vette during most of the winter months anyway. I know it sounds like your paying for two trannys but in the long run you will probably want to keep the original tranny. Now you will have a new TH350 (few miles only) sitting on the floor in your garage instead of an old broken tranny. Just my 02 cents worth... Good luck

Wayne...

 

[cmegga]

The motor is built up pretty good, probably 330-350 HP or so.

Fixing the old would be the most economical thing, but with this new gear turning 3100 RPM on the highway I feel like I have to go for a 4 speed if I can aford so. That high rpm on the high cant be great for the motor. It was something I was planning on doing anyway , just not this soon !

It looks like I can get the tranie for $866 , its the level one they rate it for up to 350 HP. If it is truly just a drop on tranie I should be able to swing it. Well see when bowtie gets back to me about what else has to be changed to make it work.

They say on their site it is a bolt in fit for the TH350, but this trannie Im pulling out of my 1981 is actually a Th350 C . Im not sure if that makes a big impact on the swap or not ....

 

[cruisin-davey-g]

cruisin-davey-g

It launched terrific , I have a 2 mile ride back to work from the mechanics shop, I had it sideways 3 times when I first picked it up. It also felt like it had alot more in the mid range to, at 50 to 60 it took real good. It was definitly the right choice of gear, thanks again for all your feed back with that. If not for you I probably would have went with a 3:36 and not been happy.

I asume I droped 3rd gear just becuase of the operating range, that old tranie wasnt used to countinus driving at 3100 + RPM in third gear with the old 2:81 gear.

With the trannie swap I would like to be around $1200 probably $1500 max , as I broke the bank with all the other goodies this year ( gear, rearsping , shocks, etc ). And this one has VISA written all over it.

Looking at the numbers Maineshark was so kind to post, I think the 200-4R: would be the best fit for me. A higher fist gear then I have now in the TH350 and a decent overdirve. This is probably the one Im going to look for , from what it sounds like I wont have to many other mods as to get it in.

I anyone has a good line an a rebult unit let me know. Im going to check out the guys at Bowtie Overdrives this moring.

Thanks

Hey, Glad 'ya like the launch! I'm a "launch-man" myself. If your driving the car mostly on the street, launch is everything! It is definately an attenion getter. Will impress some & intimadate others. On the subject of trans swaps & things. First off, I need to correct myself on a couple of issues I told you earlier (sometimes I'm so worried about my typing;not good; that I sometimes get things mixed up). On the subject of the TH400 trans: I maent that the earlier 60's TH400's are better trans in that they have more intermediate clutches (not sprags) & have heavy duty sprags. It also has a better front pump (important if your running a non-stock converter). Now that I got that cleared up, I think "Wayne's" answer above is a good one. Get the TH350 rebuilt & put it in. That trannie, if rebiult by a compentent shop, will work OK for you in your situation. And, I'm assuming that you only drive the car for pleasure, 3100 RPM's at 70MPH won't be an issue. The trans will hold up. If you got bucks, go ahead & put in the overdrive trannie. But, remember, if you do break the overdrive trans, it's quite abit more expensive to repair than the TH350 or Th400. In my opinion, putting in an overdrive trans would be a waste of money & time, for what your are using your Vette for. If you've never done an overdrive trans conversion, it can be a real headache & end up costing you more than expected. Also, if you decide to rebuild the 350 trans, you can always put alittle more into it & have it beefed up & that would be much better. These are just my general thoughts on the issue & my 2 pennies worth. What ever you decide to do, good luck on you project.

Dave

 

[MaineShark]

The TH350C is the lockup version of the TH350, correct? That might mean that you can re-use your torque converter. You'll have to ask Bowtie.

According to my emails with them about a 200-4R swap, the following parts are needed (in addition to the tranny):

Torque converter (well, maybe not, in your case)
TV cable ($95)
Pressure guage (for setup) ($29)
Dipstick ($44)
Inspection cover ($25)
Speedo gear ($44)
Brake pedal switch for lockup disconnect (maybe you already have this) ($12)
Wiring for switch (again, maybe this is already there) ($16)
Shifter conversion kit ($90)

So, you're looking at a minimum of $327 in accessories, up to $509. So, $1193-1375, total, with the Level One transmission.

Joe

 

[page62]

I have a friend in England who's doing a 200-4R swap on an '81 right now. I did mine last year. All I can say is: Go for it! Don't waste your money rebuilding the TH350c when the cash can go towards an OD unit.

I know you're not rich, but you should still go for the Level 2 unit. The Level 1 tranny uses OEM-grade parts, while the Level 2 uses better-quality bits. Also purchase the TV Made EZ kit. You will not regret it!

You'll also have to find a tranny crossmember from a '75-'79 C3. There should be one in a junkyard somewhere around you. The '81 stock crossmember does not work for some reason. (My British friend found out the hard way!) And the Bowtie aftermarket x-member isn't fitting too well for him, either.

 

[cruisin-davey-g]

cmegga: Sounds like you're getting alot of advise about the OD conversion. So, doing it yourself might not be a hard as expected. I keep forgetting that this "Forum" is an abundence of info; silly me. Like I said, if you've got the bucks, go for the conversion. But, it just seems to me that if all you're worried about is that high R's issue & you end up driving it more on the street, than on the open road. Then the difference in costs between these two issues (rebuilding the TH350 vs. OD trannie) is more than what I would be willing to pay for. I'd take that extra money that I'd be saving & put it into something else on the car. Just my thoughts. And then there's that issue if the OD trannie should break somewhere down the road; the repair costs of the OD trannie vs. repair costs of the 350. I've had buddies that have done OD's in their cars (not necessarily Vettes) & have pounded on them a lot, only to have 'em break & be costly. It would be nice to have a real close friend in the Trans Business who will help you out in time of need when doing these kinds of swaps & such. I wouldn't put a OEM stock type OD auto trans behind a high performance motor & expect it to last & the beefier OD trans are "pricey". Now, manuals; hey, that's a different story! Good Luck!


Dave

 

[cmegga]

Here is what they quoted me as bare minimums .. oooch Not quite the bolt replacement as I was expecting

Transmission: 2004R Level 1 $866.00
Torque Converter: 2200 Heavy Duty 1 $154.00
Crossmember: 80-81 Corvette Standard rubber mounts $179.00
Shifter: 77-81 Corvette $90.00
Inspection Cover: Has Own/Not Ours $0.00
Dipstick: 2004R $44.00
TV System: TV Made Ez $95.00
TCC Wiring: TCC Relay Kit 1$28.00
Speedometer Gears Drive Gear: 10 Driven Gear: 28 $44.00
Installation Tools Cost
Pressure Gauge $29.00
Inline Filter $19.00
Misc Items Cost
The $100.00 Super Deal! $-100.00

Sub Total $1,448.00
Tax $0.00
S&H $194.56
Total $1,642.56

 

[cruisin-davey-g]

cmegga: Looks like that OD conversion is starting to get "pricey". Looking at a logicial piont of view, I really don't think this is the way to go. I don't know what this shop, your dealing with, termination is of a "Level 1" OD trans is, but it sounds like it's not much more than a stock OD trans. I'd be leery about putting a stock or almost stock OD trans behing a high performance V-8 that will be "getting-on-it" alot (I'm assuming). You have to remember that most of the OD trannies were put into passenger vechiles with economy in mind & to please the Goverment Standards for autos. Using these transmissions in applications other for which they were intended for, can be asking for trouble. Now, I know there are shops all the across the good 'ole US of A re-working & massaging these transmissions, because there now seems to be a demand for them in hi-po applications. But, like everything else, comes the price tag for these conversions. So, logic tells me that if you want a really good OD trans that will be the most dependable for you hi-po application, then your gonna pay big bucks for it. I wouldn't be willing to do that. Now, you could take those monies, go to a race trannie shop, & get yourself a really good beefed-up rebuid of your TH350 (or better yet, you could get a TH400) all for less than what your facing. But, the final decision is yours & whatever you decide, good luck in your project.

Dave

 

[cmegga]

With that figure its definitly more then I can afrord and the moment, so maybe down the road a bit more.

So I guess I need to know what I should have done to that old 350 to beaf it up ??

Also is it possible for them to just change the 3rd gear in the tranie while rebuilding ?? Just a thought, I dont hit 3rd until highway speeds anyway. If I could put a smaller 3rd gear it might help to solve the RPM milage issuse. Which I would love it I can even be done.

As this is a daily driver here , well in the summer anyway ( PS New York).

 

[cruisin-davey-g]

With that figure its definitly more then I can afrord and the moment, so maybe down the road a bit more.

So I guess I need to know what I should have done to that old 350 to beaf it up ??

Also is it possible for them to just change the 3rd gear in the tranie while rebuilding ?? Just a thought, I dont hit 3rd until highway speeds anyway. If I could put a smaller 3rd gear it might help to solve the RPM milage issuse. Which I would love it I can even be done.

As this is a daily driver here , well in the summer anyway ( PS New York).

cmegga: How much highway driving do you REALLY do? I can remember back in the "Good 'OLE Days" when we didn't have the luxury of deciding for or against OD trannies (never had 'em to begin with). Now, I talked to a few of my buddies about your 3100 RPM's @ 70 & they couldn't believe your that worried about it. They say that the OD trannies are nice, but alot of money. If you're only driving your Vette in the summer, even though its on a daily basis, I'd still opt for the TH350 rebuild. Just more thoughts on the subject.

Dave

 

[cmegga]

I just dont want to run into the fix onr thing break another agian.

What im really worrie about is the aditional wear on the motor, the thing that makes me nervous is on a 10 min highway ride the temp went from its normal 205 to almost 220. I know the high temp can cause additional problems as well. And if its rasing them temp it as to be working the motor pretty hard .. right ??

 

[cruisin-davey-g]

I just dont want to run into the fix onr thing break another agian.

What im really worrie about is the aditional wear on the motor, the thing that makes me nervous is on a 10 min highway ride the temp went from its normal 205 to almost 220. I know the high temp can cause additional problems as well. And if its rasing them temp it as to be working the motor pretty hard .. right ??

you're running 205? what's your thermostat rated at? 220 is a little high, especially when it gets real hot out. About your motor. Is it the original motor & did you bore it out? If so, how much over?

 

[92ghost]

Cemmega: I hope your not thinking we're trying to tell you what to do with all our comments. It's always better to get as much info before making a decission, and I think your making the right one. Now for your question on replacing 3rd gear only. Find a reputable/trustworthy transmission repair shop in the area and there should be plenty. Ask around if you need some help but stick to a performance shop if possible. Pull the tranney and take it to them and tell em what happened to 3rd. They should ask you what engine you have, how much HP/TQ etc. and how you will be driving the vette. Let them tare into it and see what is bad or salvagable and get back to you with their recommendation. It all depends on what the insides look like and I'm not a transmission expert so I can't tell you what to look for. If you want you can ask for all the old parts that they replaced. As far as what to beaf up to make stronger so this delema does'nt happen again, the answer is with the repair shop mechanic. I have seen TH350's run with 600 HP engines at the track with no ill affect on the transmission. They use Kevlar discs and a lot more hi-performance upgrades to keep it together but it is possible. You won't need this extream upgrade. I had the same trans on my 72 Camaro rebuilt last spring. I paid $700 for the trans rebuild and some minor upgrades. I had to buy a new torque converter and that was an additional $250. I would suggest getting a new TC just to be safe. Good luck and keep us posted...

Wayne.