How do you know you're going 60? Did you change the speedo gears when you changed the rearend? 4000 rpm would be like having 5.38's in the back.

 

Couple of questions?

1. Are you sure about the tranny, torque converter and rear axle ratio?

2. Is your tach right. Have you tried a differnt tach?

3. Do you have enough fluid in the transmission?

 

I changed the gears in the tranny when I installed the rearend (also had my GPS unit in my lap and speed is right on! Checked the fluid in tranny and was good ( have a big tanny cooler on it). The tach have not checked but can tell it is running hicgh rpms. As far as the stall and tranny I just know what I was told by the previous owner! I hope this helps figure out the problem. Im very new at this ole car thing and havent turned alot of wrenches but Do enjoy it and have had good luck so far with rear end swap. Any Ideas on problem?

 

Gotta go with Bowtie on this one. Are you sure you're runnin 60? Don't trust the speedo. You need to follow behind someone that has an accurate speedo, have them get it up to 60 and then see what kind of rpm's you're runnin. Then we can go from there.

 

It sounds like you're certain about 60. The converter shouldn't have anything to do with it. It almost sounds like the tranny isn't shifting into third. 4000 at 60 with 3.73's sounds about right in second.

 

Plug you numbers into this calculator it might help with the diagnosis - http://mail.groupwhere.org/firebird/speedo.php

Here's what I got when I plug your numbers in:

TIRE - Width: 10.83 inches, Sidewall height: 6.5 inches
Diameter: 27.99 in, Circumference: 87.94 in, Revolutions per mile: 720
You need a driven gear with 26 teeth
Ratios for this transmission are: 2.52:1.52:1
Overall ratio in first gear: 9.3996
Engine RPM at 30mph in 2nd (next to final gear): 2042.45
Engine RPM at 40mph in 2nd (next to final gear): 2720.55
Engine RPM at 40mph (final gear): 1789.83
Engine RPM at 55mph (final gear): 2461.69
Engine RPM at 70mph (final gear): 2999.18
Engine RPM at 90mph (final gear): 4031.16

Looks like it's not shifting

Here's another calculator - http://www.angelfire.com/fl/procrastination/rear.html

From this one I'd say your stuck in 2nd gear.

 

I have a problem getting it to shift to L1 (shifter out of allingment) but it put into L2 and will run good and will shift from L1 to L 2 and i shift to D and it shifts and pulls good. I am possitive on speed and rear gears. Checked the oil when I got back from a 4 mile drive with car in N and idleing, have a braided line style dipstick and fluid is between the hash marks? I just dont get it, not the best wrench but have good mechanical apptitude( Im an civil engineer tech) any help or other things to check would be great.

 

Can anyone else possibbly think of anything else that might make the rpm s run so high?

 

I am guessing you checked the kickdown cable and vac modulator , What is the manifold vac? Do you feel 2 distinct shift points? Does the trans downshift if you put it in L2 from drive? The fliud level should be rite at the trans pan gasket. How does the fluid smell (burnt)?

 

you have to check trans level in park. on level ground and warm. Sounds to me like your conveter is slipping or it stuck in second.... When you driving in drive at 60 (4000 RPM) when you nail it does it feel like it is slipping...go 60 let off throttle then esae back into throttle it shoul;d be almost a direct speed between rpms and speed. iof it feels solid then i think you have it in third. stomp on it from a stop and make shore you feel two good shifts. then go 60 mph with out slowing down and get your rpms

 

I think its not shifting into D for some reason? I feel 1 good shift at 35 mph or so and thats it if I get on it, I feel a shift? pretty light if it is around 15 mph and another good one around 30 if I take it easy. I dont know what to do next, sometimes feels like a good shift and some kind of week. But know matter how I drive it 4000 rpm at 60mph wich I triple checked with GPS unit. Im about ready to hunt down the seller and take some $ out of his hide, told me just rebuilt but would only let me take it around his subdivision wich is 30 mph cuz he took the insurance of it, I m starting to believe I good screwed and never even kissed! Any other tips or things to look at please let me know. Thanks Trav

 

It sounds like your in L2 and the tranny shifter linkage may need to be adjusted. Check shifter linkage for binding or something keeping it from going
into drive. If this car was all rebuilt recently the shifter linkage probably just needs adjusted.Hope this helps.

 

I just adjusted the shifter linkage and no help, but the shifter and tranny both into D and rehooked everthing up and not any better. 3000 rpm im running 45 mph or so, wich is crazy. Im at a loss, dont know what to try next, may be a cheap fix or something major. Im n ot the most mechanicly inclined person but I think it has to internal or some kind of adjustment. I have not done anything with the tranny except change the speedo gears. Anyother suggestions on what it may be Thanks Trav.

 

Well,
You could try turning the driveshaft and count the revolutions to see if you really have 3.73's--maybe someone goofed!

 

Already did that. 3 and 3/4 turns on the drive shaft to 1 turn on the tire, Im at a total loss. This is driving me nuts, not being able to figure this out, What can it be? Thanks in advance Trav

 

You didn't do the modifications to the transmission/rear end? Maybe the guy you got the transmission from modified the shift points of the transmission. Not to sure how that works on the TH350 tranny if the shift is run purely off of the vacuum modulator or TV valve, or whatever it is, but I doubt it. I rebuilt the transmission in my camaro, a 700r4 and modified the shifting to accommodate the 4.10 gears I put in the car. Your torque converter should not have any effect on shift point. If you have a tach gauge you can usually find the stall speed of the torque converter just by watching the gauge when you start the car. It'll usually flare to the torque converter stall speed. Others have told me that you can foot brake the car and see where the tires start to brake loose to find your stall speed, I don't know how much I buy into that theory.

 

I installed the 9" rear but not the tranny(except to change speedo gears) I checke the are the 3.70 gear ratio. Dont know on the stall was told 3000 but dont believe that should change the operating rpms and mph calculations much if at all.

 

Did my own little test on this. I took my buddies Camaro out. It's got a 383 with a TH350 and 3.73 gears in a 12 bolt. Guess what rpm's it ran at 60 in 2nd gear- 4000. Sounds like you're not gettin 3rd. I can't think of any external adjustments that could cause this other than shift linkage. Unfortunately it might be screwed on the inside.

 

Why not put it into second instead of drive and take it for a spin. Once the motor gets up to 3500 rpm or so in second gear, let off the gas just a bit and put it into drive. If the rpms dont drop and you dont feel anything, it isnt going into third.

Just my advice. But like alot of others have said, I dont think it is going in final gear.

-dan

 

Can anyelse think what might be the problem? Im trying to get out of work early someday and taking it to a tranny shop and have them run it for ideas, but when you work 50 - 60 hours a week its hard to get there when there open. Seems to shift twice, I adjusted the shifter cable to make sure not between gears, checked fluid, checked everthing I can think of. Do you think a problem with the tranny cooler being plugged? I dont know trying to think of anything. Please help and when I figure it out I will post wat it is or was. Thanks guys

 

I've got an 89 Ford pickup that a guy gave me for next to nothing. He said the tranny (C6) was bad. It would go into reverse and drive perfectly, but in drive it wouldn't shift out of first. I could manually shift it and it would shift from 1st to 2nd but no 3rd at all. The modulator valve (which is one part of the system that tells your transmission to shift to another gear) was bad. Could be that it's that simple.

Worst case, a 350TH is only about $350-$400 to overhaul with a good shift kit. I've been down this same road buying a car that was supposed to be all redone (and this was from a "friend") and it was a turd. But I've learned a lot and the car is great now.

 

I traded a custom chopper I was building (70 % complete)for this and love the car and so does the wife and kids. Im a civil engineer tech. and work long hours monday thru friday and was fair to the kids to get a sitter and take the bike out so now we get the car out and do family things. Me and my dad and 6 year old son work on it togher and is great bonding and learning time and love it. But finacially it is starting to suck!!! He cobbled alot of stuff toghter but you would never know untill you tore it apart. My thought is do it once and do it right!! I spent alot of my $$ on new 9" with disk brakes, new leaf springs and frame connectors and new drive shaft and have this problem. I did the rearend when I first got it before I put any miles on itcuz had 4.56 gears and I wanted it to be more streetable, if I would have know this I would have done this first. Can you get the bolts out and drop the tranny from under the car with a big block in it? Looks really tight, distributor is really really close to the firewall. Thanks for the info so far guys.

 

It should come right out with no problem. My biggest problem was getting the car high enough to get the tranny out from under the car on the trans jack. I've found that basically everything I was told about my car was not true...fresh engine? Bullcrap! Fresh trans? Bullcrap! New posi unit?Bullcrap! I got hosed on my car but it won't happen again. I'll never buy a partially finished car again.

The only way you'll be happy with it is if you go through the transmission and have it done right...or that's my way of thinking anyway. I know what you mean about spending big $$$ on the car. But once it's done you'll really have a nice car that's done right.

 

Tranny Slipping?

Hey Now. The tranny is only in 2nd gear. The shift is not going to 3rd. Turbo 350, Stuck govenor weights, or sticking weights. vacuum modulator not adjusted or leaking vacuum to modulator. Respectfully, "Bill's" II

 

I think Bill is right. First think I thought of was governor. Shouldn't need to pull the trans to check that.

 

Governor? I dont know what this, where it is, or how to see if its bad? Please explain some please. Sorry I really new at this but want to learn. Thanks

 

Thats what I was thinkin' BOWTIE !

 

I would pull a vacuume (15Hg) on the modulator valve and take it for a ride. check the tv cable make sure its not pinched or stuck or kinked even if it is disconnected. maybe just change the modulator valve for ****s and giggles. make sure you have good manifold vac signal. if you have a 300 psi gauge find the test port it is just behind the manual valve. You should have 55-70 psi @ idle in drive 150 or so WOT

 

does a 350 have a tv cable?