To Cool Tranny or Not To Cool?

[UKPaul]

I'm probably a bit late for this post but I'll reply anyway!

You definately need the stock type rad with inbuilt trans fluid cooler. Period. I've fitted A BTO 200-4r in my '81. When I fitted the OD unit I also fitted a trans temp fluid guage. It's quite revealing. With the stock cooling system (new rad fitted) I found that the ideal trans temp of 150 deg was being slightly exceeded when in OD with the converter locked. If I ran in OD with the converter unlocked, or used one of the lower gears, the fluid temp rapidly climbed & kept climbing. A lot. I fitted a small external cooler in the return line to the tranny coming from the rad. The rad will now help to warm up the tranny fluid quickly from cold & then do it's normal job of cooling the fluid. The cooled fluid then passes through the external cooler & goes back to the trans. We haven't got Texas weather here, but I did some testing on a day where the ambient hit 100F here. Testing involved lots of WOT runs & everything I could do to increase the temps. What I found was that the tranny temp was running, as usual, about 130 when in OD with the converter locked, & was just above 150 (the ideal temp) when cruising in any other gear. I'd taken the entire A/C system out the previous winter (not expecting a record breaking summer!) so cooling will be more efficient due to no condenser in front of the rad. Really I should have got the smallest external cooler I could have as it's slightly overcooling it now. Fitting a large cooler could mean that you'll end up running it at to low a temp. A temp guage is very well worth fitting. And another bonus of the external cooler is that the coolant temp always stays at 180 (the stat rating) & I've never got it near, let alone above, the 200 mark. Prior to fitting the external tranny cooler my coolant temp was normally 200 or above (with both the th350C & 200-4r). But I mention this to people & they look at me like I'm crazy.......
Any reason you're going for a 700-r rather than a 200???
Cheers

 

[Macgyver]

THanks for the reply UKPaul, I decided to be very patient and return the radiator wait for the credit and then purchase another. Im fitting it all in tonight. Ialready have the rad in but I forgot about the shroud becuase I had it sitting in the backyard after I cleaned it off. The one I got is close to OEM just a little longer. I dont know if the one in there was OEM in the first place cuase it was made of plastic, so I doubt it. The new one looks great, one piece alum, and has the tranny provisions.

I was under the impression that the first gear in the 700r had some great getup and ran your engine at lower RPMs on the highway. I do a lot of highway driving and i like to drive very fast as well. I would love to be @3000 RPMS at 100-110 mph. Most think Im an idiot but hey if youve always driven fast then your just as good as someone whose always drivin 70mph. Is the 200 just about the same in performance? It fits right up in place of the 350th unlike the 700r doesnt it?

Whats the optimum tranny fluid temp anyways 150-180?

 

[UKPaul]

Hi,
Did you fit the rad & forget to put the shroud in 1st? If so, you aren't alone!!
The 700 1st gear is much lower than the 200 1st gear, but there's a big change going into 2nd, meaning that the rev drop from 1st to 2nd is a lot more on the 700 than on the 200. I also do a lot of highway driving & that's the reason I put the 200-r4 in (fuel costs are extortionate here & with Headers, duals & Monza "mufflers" the noise level at highway speeds was a real attention getter - esp from the cops ). The rear ratio on my '81 is 2.87 & I'm now doing 75mph at 2000rpm with the converter locked in OD. It's excellent, even in the year I've had it the savings in fuel costs have been considerable. I reckon in 3 years the tranny would have paid for itself. Even better is that the cruising speed is now comparable to any modern car
The 200 1st gear isn't as low as the 700 & I think the OD gear is very, very slightly higher. The really nice thing about the 200 is that it drops right in behind the motor in place of the Th350C & no driveshaft mods are needed - it's almost plug & play. With an '81 you'll definately need a custom x-member as so many modifications will be needed to the stock one that it'd be easier to fabricate one from scratch. The Bowtie x-member is a must have if you're doing the swap. I measured everything up after fitting it & the driveshaft is held in exactly the same position as with the stock setup. Additionally, the BTO x-member allows you to fit true dual pipes as it kinks up for clearance on both the passenger & driver side (the only limiting thing then is the drivers floor pan).
The only "problem" with the 200-r4 is that it'll stay in OD when you slow down. Apparently OD trannys don't like being run at low speed in OD & the general consensus is that at anything below 65mph just manually knock it into 3 (same gearing as D in the stock TH350C) & just use OD on the highway. I was originally going to get a 700 but driveshaft mods would be required & a few people with 700's said that if they were to do it again they'd fit the 200 due to the even gear spacing & less hassle in the swap. Something else I heard was that 200's are inherently weak, but they're fitted in GN's & there's Vettes with much more power than my '81 running them with no problems. The BTO level 2 (what I got) can handle 400 (450?) hp & lbft happily. It'd be nice to have to worry about breaking it, but I've got nowhere near that much power coming out of my L81 (yet ).
The BTO website keeps praising them with words like "wonderful" etc, etc. Having fitted one I can say that they don't praise them enough, it's the best mod that I've done to the Vette & I can't think of any other mod I could do that would give such a massive increase in driving pleasure (as the motoring journalists say). Not even a ZZ4 with twin turbos (although it'd be fun!). Something nobody has mentioned is the effect on C4 & C5 owners. When they're cruising at your sort of cruising speeds their mouths just drop open when an old C3 purrs up alongside them at about 3000rpms. The looks on their faces has gotta be worth at least some of the cost of the swap :L

edit: optimum tranny fluid temp is 150deg.

 

[Macgyver]

Hmmm... If its not going to cost me another $500+ in extra parts and labor then maybe I will go w/ that one. Theyre the price anyways and youre rigtht the 60mph rpms are like 200rpm difference. Maybe then this will be in the even sooner future. Id like to get all the mechanical stuff done by mid May so that I can have a great cruisin summer.