Double Aught

I will be getting my car back from the Vette shop in a day or two. They said the tranny is not a bolt in unit. The new crossmember changed the angle of the engine block, causing the fan to hit the radiator shroud. They had to take out the crossmember and modify it to fit. I will find out exactly what they did when I pick up the car. Anyone else run into this or other problems?

Shark Racer

Biggest problem was the throttle linkage/TV Cable. They reccommended that it was set a certain way, and the transmission shifted like crap that way. You used the crossmember BTO sells? My guys had no problem, maybe your guys shimmed wrong, or a motor mount was bad.

*edit from 2012*

In case anyone is back in time reading this thread, I think the shop that installed my BTO 700R4 did a horrible job. BTO has the right idea, I just had my faith in the wrong people. Please ignore my response.

Chris69

I've also got the BTO tranny and the crossmember wasn't right. The parking brake pulley bracket hit the floorpan and the angle was all wrong. And, of course, the exhaust pipes wouldn't clear it so ended up modifying the original crossmember.

Also going through the TV cable setup woes. Like Steve said, if you set it up like they want you to, it shifts with a kick in the pants. Not too bad, but certainly not smooth, although catching rubber in 2nd & 3rd can be fun... They said they were coming out with a better linkage adapter that will help fine tune the shifting. Guessing their main concern is keeping the pressure up and less with the shift quality for warranty purposes. Steve... what was your experience with the TV system and did you get it the way you like it? I haven't messed with mine yet.

TedH

Biggest problems I have had with my BTO kit:

Fluid level - Per BTO you can't trust the dipstick and only remedy is to pull pan and establish full point using their instructions. Mine was .5-1 quart over filled until last night when I drained approximately that amount. Now shifts properly and right on full (forget pulling the pan; not gonna happen).

Shifter Reverse Lock-out - My shifter doesn't prevent D-N-R shift that I discovered when I was at stop and proceeded to move shifter to N to find that it stopped in R-everse! Actually, the lock-out is a bit reversed as I can go from R to N and then have to press the button to go to D-rive. Not sure if this is due to my hammering on the shifter to break the resistant welds on the old shifter pattern or if I broke something (perhaps the latter) in the shifter.

Leak at tailshaft - I suspect this related to overfilling early on. I also had to swap the speedo gear as they sent for 3.08 and I had changed to 3.54. Not sure if one of the rubber seals that go around the aluminum speedo unit are 'off' or if just leaking. Will keep an eye on now that I've removed the .5-1 qt of fluid.

Parking Brake - Had to hammer the floor to clear the pulley and still have a parking brake cable that is limp and not sure what to do to adjust it to make my parking brake usable. Had no other choice as BTO said the pully was positioned correctly (per .jpg I sent them) even though it is obvious the mount points up to the floor at an angle and floor clearance is a problem.

Trans Lines - Save yourself the aggravation and install new lines for the 700R4 (82 Corvette). I've had to loosen/tighten them more than I prefer and still have minor seepage. Gotta get those new lines...

Exhaust - bought a true duals setup for 74-79 vettes from Mid-Am. Ended up ditching the pipes at the manifolds due to bends that sent the pipes into my x-member. Chose instead to use the two 2.5" sections from my front y-pipe (catalytic car), sections of 2.5" pipe from Summit, and then the rear exhaust pipes from the kit with my Dynomax Super Turbos that I had salvaged from my old system. Got some welding to do to clean up the connections...

TV Cable - Had to play with that for a while. Guitar string tight (as recommended by Chevy High Performance) was neck-snapping. Backed TV off to about 1" from seated. Shifts better (softer and sooner) and car exits overdrive when I tap the brake (have used the wiring kit from BTO for overdrive release).

Driveshaft Installation - I found that removal of the rear differential with driveshaft attached (and re-installation in this manner) was only way to install the driveshaft after trans installation. Didn't help having to attach the differential snout mount AFTER the driveshaft guided into the tail of trans and balancing the diff on a large floor jack. Quite a few scratches and bruises from this effort.

1-2 shift - Still causes my carbureted engine to shudder/stumble when under hard acceleration and the trans drops rpms about 750! Am hoping that when I have the car dialed in at local dyno shop that we can richen/adjust carb and timing to resolve the stumble. Doesn't stumble if shifting under less load.

Recommendation: rebuild and blueprint the driveshaft, differential, half shafts and rear bearing assemblies (if not already performed). This trans shifts harder and the 1-2 shift is bound to break something if near end of useful life (u-joints or Dana 44 aluminum diff housing).

Double Aught

I talked with my mechanic today and this is what is happening. The installation shifted the engine angle upwards, causing the fan to hit the shroud. So, he jacked up the back of the trans and it fixed the problem. (I think he shimmed it) Then, it goes to the muffler shop, who specialize in Vette exhaust. The crossmember interferes with the proper alignment of the exhaust. He calls Steve and lo and behold, someone emailed them concerning the very same problem in a 76. So, now BTO is checking the crossmembers they have in-stock to see if it is a manufacture problem.
Tedh: I didn't run into any of the problems you described or at least they haven't told me about them yet. My mechanic said it went in without a hitch.


[Modified by sd pacecar, 6:20 PM 11/29/2001]


[Modified by sd pacecar, 8:34 PM 11/29/2001]

cbyrd74

I did the BTO conversion on my 74 and the only thing that was a problem was the driveshaft clearance. I had the shaft shorted but I did not change the end of the shaft to a 350 style, I used a hybrid U-Joint . I had to shift the rear of the tranny to the driver side about 1/4 inch to keep the yoke of the driveshaft from hitting the driveshaft channel. I did not have to shimm the tranny up at all.

I did have to have all new exhaust installed from the manifold back to the muffler.
I think that after you have setup the tranny using BTO's instructions, you can change the aggressiveness buy changing the position of the linkage on the carb. My does not shift to radical unless I have it set in the very forward position.

just my .02 :)

PS. BTO was very good to work with on all of the install and testdrive.

jeffs

I did the BTO swap in my 1978 last year. I used a little adapter plate that bolts to the original crossmember. Everything really worked out very good as far as part clearance during the re-installation. You must have received the wrong crossmember.

After initial installation everything drove fine, I did have a new modulator put in to get it to shift at 5500, however, now after about 700 miles the shift at WOT has changed and is now at 3000 rpm. I'm thinking the problem is either this new modulator or that little plunger thingyabob that the TV cable connects to is sticking. BTO has a kit for a sticky plunger thingyabob so this could be a clue and maybe will be my first check.

As far as the shift feel I actually had too soft of shifts. I was thinking of putting a medium shift kit in next summer. Maybe after I get the TV setup figured out I wont need a shift kit. I have swaped carbs since the initial install.

Where can I get a second opinion on TV adjustment other that BTO?

Jeffs

spokewrench

Wow! what aggravation, you guys have the patience of a saint! I was seriously considering this swap, but between talking to local trans. shops they
convinced me that no matter what you do to a 700r it will never hold up as well
or long as my turbo400. and then to hear all these problems, Its not for me!
I figure it this way, if you drive 5000 miles a year and your car gets 10mpg with t-400 and 3.70 gears = 5000/10 = 500 gals x $1.20 per gal = $600 per
year. Now if with a 700r you double this milage(very unlikely) then 5000/20=250 gals x $1.20 per gal. = $300.00 per year. for a savingings of
$300.00 per year fuel savings.
Cost of swap:
shorten and bal. driveshaft= $150.00
shifter conv. kit = $100.00
wire = $16.00
speedo kit = $44.00
dipstick =$ 22.00
crossmember = $179.00
cover = $ 22.00
convertor = $ 155.00
trans= = $866.00
freight $185.00
------------------------------------------
$1739.00/ $300. fuel saving per year = 5.8 yrs!
New muffler system $400.00
installation $300.00
misc.parts $100.00
-------------------------------------------
Grand total $2539.00/$300.00 fuel savings per year = 8.5 yrs!

fauxrs

spokewrench:

If you are trying to pay back the cost due to fuel savings you are absolutely correct however, factor in the absolute fun of the nice low (high numericly) first gear in the tranny for excellent off the line performance - the increased top speed of the car due to gearing, the ability to drive on the freeway with the car not having to turn 4000 rpm all the time.....all of which, while difficult to place a monetary value on, may be enough for many to rationalize the expense.

I'm looking to do a 5 or 6 speed manual conversion to my 4-spd equipped car and the same reasoning applies - but I'm looking at driving pleasure in addition to fuel savings, motor longevity etc....

To each his own.


[Modified by fauxrs, 11:36 AM 11/30/2001]

spokewrench

I definately agree there are some nice benifits to this swap, I was already to jump myself, I just feel the negatives out way the positives, especially in my case where I would be giving up some durability, I also did not mean to insult anyone just wanted to share the way I figured it.
SPOKE-

cbyrd74

Just to follow up.

I LOVE my 700R4. It makes driving more fun. I can cruse at 70 with a RPM of 1950. The car runs cooler and the AC works good!. And alot less noise.

I have talked to several tranny guys and they say the700R4 can take a lot of abuse and handle alot of torque. The biggest problem is if you dont set the tranny up so that the pressures are right you will burn it up.

Another .02. That makes .04!

Carl in LA

I can't offer any thoughts on trouble with installing the BTO 700 because I am about three weeks away from doing mine!!!! My engine is at the rebuilder getting a 383 rebuild.

I can offer another reason for getting the overdrive tranny... driving range. I expect overdrive mileage on the new 383 to be over 20mpg. My old mileage was about 11 mpg and my range was about 100 miles before the needle showed E... with the overdrive tranny I can expect to double that and enjoy cruises with modern vettes in the local corvette club. 100 miles to E just won't get it done!

By the way... about the price of a BTO 700R4... I have a junk yard in the area that rebuilds 700s and resells them at $550... Somehow I think that extra $300 is worth it for the piece of mind.

DR700R4

After hearing about this shroud problem, we got a Corvette in to check the fit and we found a problem with our welding jig. It has now been corrected. If anyone has a cross member that the fan hit the shroud please contact us for a free replacement. Sorry about this problem.

We are working on a revised design of a cross member that will clear all stock exhausts systems without modification. We are also designing it so you can run very large aftermarket exhausts and run them almost straight back.

Your local exhaust shop will have to attach exhaust hangers onto the cross member as needed to support the exhaust.

Sincerely

Steve Holmes
Bow Tie Overdrives

Stingy74

I thought my car would be faster in top speed with the 700-r4 but it wasn't. With the 3.08 gears I had at the time the engine couldn't pull hard enough in the .70 overdrive gear, and that's with my hotrod engine that peaks at 6500rpm. When I switched to 4.11's I could actually grab 6500 in OD. The 4.11's helped me put the car in a better power range when in OD.

Here's a few calculations I made with a program i've got.

3.08, 1:1 (3rd gear), 6500rpm = 161mph
3.08, .70 (overdrive), 4500rpm= 159mph

There's some small inconsistancies within the formula but as soon as I shifted in from 3rd to 4th the speed didn't really climb. Only the revs dropped. All I could get in OD with the 3.08's was 4500rpm, no more.

4.11, 1:1 (3rd gear) 6500rpm = 120mph
4.11, .70 (overdrive) 6500rpm= 172mph

I like the 4.11's alot better with the 700-R4, too bad I allready sold them.

Shark Racer

Chris-I had my guys set the transmission a little softer, and it shifted just fine after that. However, when mine was set improperly, not only did it shift hard, it also shifted late. Furthermore, it would freewheel at speeds below 20 mph or so, and this was a MAAAAAJOR pain in the butt. When driving through my complex, the transmission REFUSED to go into gear until almost 2000 rpm, so I made a large amount of noise and the car felt like it was suffering from some kind of injury, behaving like that. Now, the only hard shifts occur after ~4000 rpm.
Fuel economy has not jumped, and I'm a little disappointed, but... I think I have a problem elsewhere. (thinking carb), car got 10mpg before, on the freeway mostly, and now gets 13-15(an improvement nonetheless). Got 17 once, and was elated.
-Steve

Shark Racer

Stingy-A higher top speed should be possible with the 700R4, unless your engine just isn't capable of overcoming the drag. (Which could be possibly, 160 mph is VERY fast for a C3... the Z06 has 400 hp, is much more slippier than our car, and only does 172).
My guess would be that it's harder for the engine to overcome turning motion and fight drag in O/D. With an engine with 4.11s though, there's obviously less turning motion to resist. A car with 3.08s isn't going to get much top end help from the 700R4, however my car, with only 3.55s, red lines at ~118 mph as it is. So, for me, the 700R4 gives me an additional 20 mph or so. When I supe my motor up, I hope to be capable of the same speeds as you.
-Steve

Chris69

DR700R4.... That's great about the new crossmember. I still haven't shipped mine back yet and may just request an exchange when you folks have the new design ready. The mods made to my original xmember worked out fine, but just not as pretty. :rolleyes: Do you have that new q-jet linkage adpater available yet?

Stingy74

Yes, your exactly right. Those were just my erperiences. I've also had 3.55's behind the same engine/tranny combo but that was when it was in my 79 which I felt was a heavier car. Others here also have the 700/4.11 combo (Gkull is the first that comes to mind). For my application it was the perfect ratio. Lot's of acceleration, more than enough top speed, and decent gas milage and revs on the highway. I've currently got 4.56's that have yet to be installed but the 4.88 are also on their was strictly as a backup ratio or possibly for a spare diff if I can find a core cheap enough.

Here are some calculations with either new ratio and new engine that revs higher.

4.56, 1:1, 7000rpm = 117mph
4.56. .70, 7000rpm = 167mph

4.88, 1:1, 7000rpm = 109mph
4.88, .70, 7000rpm = 156mph

The 4.88's don't fare that bad actually and i'll never ever need to go 156mph.