Transmission slip

[Bobplane777]

I have a 79 rebuilt tranny with 700r auto. Just purchased...it was in taken out of storage for the winter and finished last season in good shape. Now hw, I noticed a little grabbing (or slipping) from 1st to 2nd... all the other gears work fine and it down shifts normally. I noticed it was a 2 Qrt + low on tran fluid so I ran and filled it to the X hot mark on the stick (after heating it up) ... but no change in grab. Fluid was changed before storage but not filled to proper level (because I havent noticed any leaks anywhere around tran).

Any ideas on how to smooth out the shift or what may be going on ?:bash

thanks!!!

 

[Hib Halverson]

I'm confused on this one. At the 1-2 shift, is it slipping? Or Grabbing? Hard to imagine it could do both.

 

[Bobplane777]

Trans grabbing

I'm confused on this one. At the 1-2 shift, is it slipping? Or Grabbing? Hard to imagine it could do both.

It would probably be best described as grabbing, it actually does not slip once in gear (bad use of terms) but feels like it goes into gear hard (vs. smooth transition).

 

[Bobplane777]

It would probably be best described as grabbing, it actually does not slip once in gear (bad use of terms) but feels like it goes into gear hard (vs. smooth transition).

It would probably be best described as grabbing, it actually does not slip once in gear (bad use of terms) but feels like it goes into gear hard (vs. smooth transition).

thks

 

[Rodney Gold]

Check for a vacuum leak or partial vac leak tween the intake manifold and the vacuum modulator. Perhaps some rubber hose has perished or split? I would also try draining the tranny fluid and using something like trickshift...

 

[Hib Halverson]

Does it shift hard going into drive from park/neutral or into reverse from park/neutral?

 

[Bobplane777]

Does it shift hard going into drive from park/neutral or into reverse from park/neutral?

Yes, 70-80% of time it feels like it grabs. Yet, 2nd thru 4th gear is smooth (above 25+ mph) and when coming to a stop it is also smooth (only when first engaged or 1st shift

thks for help!

 

[Bobplane777]

Check for a vacuum leak or partial vac leak tween the intake manifold and the vacuum modulator. Perhaps some rubber hose has perished or split? I would also try draining the tranny fluid and using something like trickshift...

I will take a look at the hoses. Is 'Trickshift' available at most auto stores? What is it correcting?

thanks for suggestions and help!
/Bob

 

[Hib Halverson]

If it hard shifts into drive, reverse and at the 1-2, shift, as "Rodney Gold" suggests, I'd carefuly check the vacuum modulator and its hoses.

Typically, products like "Trickshift" will make the problem you are having worse. Besides, if the problem is being caused by the vac. modulator, no trans fluid will fix it.

 

[Rodney Gold]

Well , we fill all modded or overhauled boxes with B&M trickshift as a matter of course , its an extreme duty ATF and helps parts survive.
B&M Trick Shift Trans Fluid - JEGS
Do you hear a noise at all when going into R or D from N?
If so , one other thing I would check is the propshaft universals.

 

[TimAT]

Thinking about TrickShift in a 700R4 makes me cringe. I guess I've built too many of them. The 700 is VERY critical of lube in the rear planetary gearset. Very tight clearances in the pinion gears, and all that gets back there comes from the front- so it's already very hot. And TrickShift is basically FORD Type F fliud. Not as good a lubricant as Dexron.

From what the description of the problem is, I suggest resetting the TV cable as a beginning to diagnosis. If you have a pressure gauge that would be the very best way to set the TV cable, but lacking that, release the lock on the cable and pull the housing all the way to the rear. Then (engine off!) give it full throttle. The cable will ratchet back out to the correctly adjusted position. If you don't like the way it feels, here's the fix:
Shifts hard/late, pull the cable out so it comes out a maximum of 2 clicks
Shifts early/soft, retract it a maximum of 2 clicks.
The 700 has no vacuum control.

 

[gmjunkie]

Thinking about TrickShift in a 700R4 makes me cringe. I guess I've built too many of them. The 700 is VERY critical of lube in the rear planetary gearset. Very tight clearances in the pinion gears, and all that gets back there comes from the front- so it's already very hot. And TrickShift is basically FORD Type F fliud. Not as good a lubricant as Dexron.

From what the description of the problem is, I suggest resetting the TV cable as a beginning to diagnosis. If you have a pressure gauge that would be the very best way to set the TV cable, but lacking that, release the lock on the cable and pull the housing all the way to the rear. Then (engine off!) give it full throttle. The cable will ratchet back out to the correctly adjusted position. If you don't like the way it feels, here's the fix:
Shifts hard/late, pull the cable out so it comes out a maximum of 2 clicks
Shifts early/soft, retract it a maximum of 2 clicks.
The 700 has no vacuum control.

 

[Bobplane777]

Thanks so much for the help. Good to know not to search for vac modules if not on the 700r. I purchased the 703 page Cd and assembly guide but have not had a chance to look at it yet (I am in Japan until next week on business). I've never heard of "TV cable..." and would appreciate it if you could direct me to more information (I'm a convert from Mustang GTs days!). I've always loved the string ray look - the 79 is in good shape but I would like to see it shift smoothly.

Thanks again for your time and help (and everyone's suggestions).
/Bob

 

[Rodney Gold]

There is a mod for the 700r4 (I didnt read the first post correctly...thought it was a TH350) and that is the constant line pressure valve body , but it doesnt fit early trannys
This site is also very informative
700 Raptor 700R4 700R4 Transmission 700r4 700R4 700r4 PATC 700R4 700r4 700r4 700r4 700r4 700r4 700r4 700r4 700r4

 

[TimAT]

Not a bad article for someone trying to sell 700's. Couple of things I disagree with- 1st is the statement about the front seal- they say, QUOTE "If you have a problem with the front seal, installing a new seal is a waste of time and money, it will only leak or blow off again. You must install a new seal, torque converter and rebuild the pump all at the same time to correct this front seal leak. This should cost about $360.00 plus tax."end QUOTE.

Unless the snout on the convertor is scored or grooved not necessary to replace it. And you can install a new bushing in the front pump cover, check the drainback holes are drilled to 5/16 and 1/4, install a 10 vane pump with hardened rings, and a new seal with locktite around the OD. Done.

And rebuilding a 700 without a shift kit (IMHO) is like leaving 1/2 the clutches on the table. Why install 2 or 3 of the pieces when for about the same or less $$ you can get a good quality shift kit that has these parts PLUS additional parts to correct line pressure, TV pressure and have better "feel" for all shifts?

The other thing is not hooking up the TCC- when the TCC locks up, the pressure to the cooler jumps from about 70 psi to 125 psi. More fluid thru the cooler= better cooling.

I'm not running down that companies product, just throwing my $.02 out there for additional info.