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Hot Rod Forum : Hotrodders Bulletin Board > Tech Help> Transmission - Rearend> 1968 firebird , highway RPM way to high
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Topic Review (Newest First)
04-16-2013 11:28 AM
starin dang.. i think i'll just throw my 200R4 in and not worry about this since the transmission will be junked, i was just hoping to be able to drive it till my one week vaction next month when i do the transmission swap.

thanks for the help all
04-15-2013 11:23 PM
Originally Posted by starin View Post
i believe a piece of the spring was hanging on the hook that hood up to the detent cable when i dropped the pan the first time, how do i fix the spring? the detent definitiely does not retract.
You'll want to remove the valve and see what the spring looks like and see if the valve is hanging up in its bore or what.

Below is a drawing of the valve body. Look for "G".

04-15-2013 11:48 AM
starin i believe a piece of the spring was hanging on the hook that hood up to the detent cable when i dropped the pan the first time, how do i fix the spring? the detent definitiely does not retract.
04-15-2013 11:36 AM
cobalt327 The detent valve is spring loaded. If the spring is bad (or the valve is sticking) and the detent is positioned like the throttle was wide open this would effect the shifting.
04-15-2013 10:44 AM
starin Ok so just an update and recap, i jacked up the car and spun the tire, for one rotation of the tire the driveshaft spun 3.75 times, so i guess that equates to 3.73 gears.

I also checked my shifter linkage and drive is drive and everything is good there.

I took the car for a drive and still the same issue at, 3500 rpm im doing 58 mph using my phone gps and and a tom tom GPS with 28 inch tall tires which equates to 5.03 gears. so i think i narrowed it down to some type of problem with the transmission.

Also when i was driving i did see that the rpm did drop twice once from 1st to 2nd and another from 3rd to 4th. but it shifted gears very quickly, it shifted from 1st to 2nd at 2000 rpm and then again from 2nd to 3rd around 2000 rpm. and both gear changed happened within 6 seconds of each other.

So i'm not too sure why my rear end gear 3.73 but its still taching high.

One other thing. i do not have the detent cable from the trans hooked up. when i dropped the pan intially to change the fluid the first time in this used th350 it had a little spring just hanging from the detent hook that connect to the detent cable. also when the detent was hooked up it would not retract. lets say if the carb was wide open throttle and the cable was pulled out, it would not retract when i let off the throttle and the car would just stay in first gear wind all the way up in rpm and then shift really hard. so i just pushed the cable back in. Don't know if this would have any relation as to why my trans is gicing me such high rpm.

Thanks again
04-11-2013 11:33 AM
starin yea i don't plan to regear it, hopefully i can figure out how to drop the th350 and put in this 200R4 and call it good, i got under the car yesterday and the bell housing bolts are going to be a pain.....
04-11-2013 11:26 AM
69 widetrack With 3.73's you where probably driving in 2nd gear...3.73's for a Pontiac motor are an excellent gear. Pontiacs can be a torque monster and unless your looking at putting as many mile on the track as on the street, often a taller gear isn't needed.

04-11-2013 10:59 AM
starin Just an update because i always hate leaving hanging threads.

So i marked my driveshaft and tire with a white marker and spun the tire one rotation, the driveshaft spun 3.75 times, so i'm assuming i have 3.73 gears in it.

I then messed with my B&M automatic shift cable, the instructions say to put the trans linkage and shifter all the way in low 1. then put the car into park and make sure it's still in adjustment. Well when i had adjusted that the line on my shifter that indicates if the car is on D or R or N never reall lined up. so this time i manually moved the trans linkage to P then R and N and D etc. to make sure that each notch lined up with my shifter mark.

I havn't test drove the vehicle, can't until Saturday, but my guess hopefully is i was driving in D2 instead of Drive.
04-09-2013 11:40 AM
69 widetrack You do have a tach, correct...what you could do, again, put the car in drive, watch your tachometer, you should see your RPM rise and drop twice...if the RPM's rise and drop from 1st to 2nd and then from 2nd to Drive...then you have all three gears. If it only does it once, then you are probably running in 1st and 2nd gear only.

Another way to tell is by listening to the engine, the same thing should happen, you will hear the engine rev up and then hear it drop and rev up again and drop...On a three speed automatic this should happen twice. If it's only happening once, you'll need to get under the car and adjust the shifter linkage.

04-09-2013 11:12 AM
starin something just occured to me, the car never had a shifter so i installed the most basic shifter i could find which was a basic b&m. now i'm thinking is it possible i've been driving in d2 instead of D the whole time? how can i tell if im Drive and not in D2 the shifter is not the greatest.

thanks again for your guys input
04-08-2013 03:33 PM
big gear head My wife is pretty glad that I quit doing rear end work. She had to put up with the smell every day for 15 years. Old Ford gear oil is the worst. Some of those '50 and '60s 9 inch Fords had some really stinky oil in them.
04-08-2013 12:15 PM
cobalt327 Been there, no fun! The only thing that even begins to come close to the smell is the "dead" motor oil at the bottoms of blind main cap bolt holes of an engine w/100K miles. *pee-YOO*!
04-08-2013 12:06 PM
Originally Posted by cobalt327 View Post
A word of caution: Be sure to use a W I D E pan to catch the diff lube! It stinks to high hell, and if you get it on the floor of the shop or driveway (let alone on you or your clothes), you'll regret it.
Ahh the ol 'center-chunk funk'.

Not only will he regret the stench; his wife will make sure he never forgets it! she'll never do his laundry or let him sleep near her for a month...LOL ask me how I know
04-08-2013 11:45 AM
59 wagon man yes you are correct
04-08-2013 11:43 AM
starin i'll have to check, so reaching highway speed from a dead stop how many rpm drops should there be? one drop from 1 to 2nd and another drop from 2nd to 3rd right?
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