700R4 hesitating in DRIVE!
Thread Starter
2026 Loser of the Year
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From: New Or-leens Loo-z-anna
700R4 hesitating in DRIVE!
ROOKIE PROBLEM........
If anyone has a clue: My 700R4 that is now in my '34 street truck will soon be swapped with the TH400 that is in the Vette project inorder to drop cruising rpm and increase mpg. I will put a rebuild kit in it before the swap.
I've spent hours doing searches, but no site has a definite answer.
When hot or cold the transmission hesitates for about 5 seconds when it is shifted into DRIVE.....it doesn't hesitate at any other time.
I have installed a dash-pressure gauge, serviced the unit/tried different fluids and additives/replaced servo-seals-etc with no good results.
According to the test-charts, the operating pressures are perfect in all gears and at all speeds/it shifts itself perfectly....it has an external fluid cooler....I have always serviced it every 20,000 miles.
I think it's a valve body problem, but would rather change a $30 piston or spring, than a $250 valve body (and STILL not solve the problem).
Problem is...being a rookie....I can't decide which piston, spring, or servo in the transmission needs to be replaced.
Has anyone had/heard of a similar problem?
If anyone has a clue: My 700R4 that is now in my '34 street truck will soon be swapped with the TH400 that is in the Vette project inorder to drop cruising rpm and increase mpg. I will put a rebuild kit in it before the swap.
I've spent hours doing searches, but no site has a definite answer.
When hot or cold the transmission hesitates for about 5 seconds when it is shifted into DRIVE.....it doesn't hesitate at any other time.
I have installed a dash-pressure gauge, serviced the unit/tried different fluids and additives/replaced servo-seals-etc with no good results.
According to the test-charts, the operating pressures are perfect in all gears and at all speeds/it shifts itself perfectly....it has an external fluid cooler....I have always serviced it every 20,000 miles.
I think it's a valve body problem, but would rather change a $30 piston or spring, than a $250 valve body (and STILL not solve the problem).
Problem is...being a rookie....I can't decide which piston, spring, or servo in the transmission needs to be replaced.
Has anyone had/heard of a similar problem?
Le Mans Master
Joined: Oct 2006
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From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
When you put it in gear is the pressure rise instant or does it take that few seconds to come up?
My first thought is either the pump regulator filter has caught some trash, the pump is lazy or maybe even the lo-reverse clutches have too much clearance.
My first thought is either the pump regulator filter has caught some trash, the pump is lazy or maybe even the lo-reverse clutches have too much clearance.
Thread Starter
2026 Loser of the Year
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From: New Or-leens Loo-z-anna
I'll post the results tomorrow....with the cold and hot transmission results....and thanks for the input.
Thread Starter
2026 Loser of the Year
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From: New Or-leens Loo-z-anna
Racer
Joined: Mar 2003
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From: Klein Texas
I don't believe there is a pressure difference between park/neutral and drive. The pressure does increase when selecting reverse.
Pet peeve- I hate the term "hesitation" when describing transmission concerns. "hesitation" is an engine performance/drivability complaint.
If I had to guess, I would think the seals for the forward clutch are hardening and leaking. If you select manual 1st is it the same?
Pet peeve- I hate the term "hesitation" when describing transmission concerns. "hesitation" is an engine performance/drivability complaint.
If I had to guess, I would think the seals for the forward clutch are hardening and leaking. If you select manual 1st is it the same?
Thread Starter
2026 Loser of the Year
Joined: Sep 2013
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From: New Or-leens Loo-z-anna
I don't believe there is a pressure difference between park/neutral and drive. The pressure does increase when selecting reverse.
Pet peeve- I hate the term "hesitation" when describing transmission concerns. "hesitation" is an engine performance/drivability complaint.
If I had to guess, I would think the seals for the forward clutch are hardening and leaking. If you select manual 1st is it the same?
Pet peeve- I hate the term "hesitation" when describing transmission concerns. "hesitation" is an engine performance/drivability complaint.
If I had to guess, I would think the seals for the forward clutch are hardening and leaking. If you select manual 1st is it the same?
I drove the truck today (what would be a good term to use instead of "hesitates"?):
36*F ambient air (approx. the same results on a 95*F day/all psi readings 10% less)
80 psi cold in PARK
150 psi cold in REVERSE
80 psi cold in DRIVE with brake on
105 psi immediate rise while driving at any speed
70 psi in PARK with transmission warm ( at operating temperature)
145 psi immediate rise in REVERSE warm
70 psi in DRIVE warm with brake on
95 psi while driving at any speed
So....there is a 10 psi drop in pressure at operating temperature.
(I forgot to try 1st gear manually)
Is that enough info for you to make a conclusion....
or do you want me to do the 1st-gear manually tomorrow?
Thanks, doorgunner
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Thread Starter
2026 Loser of the Year
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From: New Or-leens Loo-z-anna
This afternoon I will drive the truck and check for delayed engagement in low gear. I'll post the results tonight.
Last edited by doorgunner; Jan 9, 2015 at 08:39 PM.
Thread Starter
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From: New Or-leens Loo-z-anna
Cold or operating temperature......when I manually shift it into low gear it still delays engagement.
So I can rule out mechanical problems............ a quality rebuild kit will give me a good solid transmission again.
So I can rule out mechanical problems............ a quality rebuild kit will give me a good solid transmission again.
Thread Starter
2026 Loser of the Year
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From: New Or-leens Loo-z-anna
Somehow.........I didn't adjust the TV cable correctly when I added the 700R4 carb linkage adapter to the Holley on my '34 SBC truck.......
it won't solve the delayed engagement problem, but it may stop the tires from "barking" when going into 2nd gear under moderate acceleration...a little rough on the neck with no headrests......LOL!
it won't solve the delayed engagement problem, but it may stop the tires from "barking" when going into 2nd gear under moderate acceleration...a little rough on the neck with no headrests......LOL!
Thread Starter
2026 Loser of the Year
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From: New Or-leens Loo-z-anna
The TV cable adjustment worked....no more neck snap with 2nd gear shift.....I must not have fully engaged the adjust-button previously and the cable tightened up some!
Now....to collect rebuild parts.
Now....to collect rebuild parts.
Le Mans Master
Joined: Oct 2006
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From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
There should be a shop that sells nothing but trans related parts- there are 2 or 3 in Kansas City that I've used. Prices vary a little between them, I usually go to the same one because the guys there seem to have a better handle on what's needed and I don't forget something. Rubber, paper and faced clutches runs about $125 IIRC. Add a front pump bushing, the 10 vane pump kit, and a filter. The ones I usually see are smoked big time so I usually get a convertor too. Out the door for between 200 and 250.
I forgot- I always get a shift kit- I prefer Superior, but had good luck with the Trans-Go kits too.
I forgot- I always get a shift kit- I prefer Superior, but had good luck with the Trans-Go kits too.
Last edited by TimAT; Jan 15, 2015 at 03:21 PM.
Thread Starter
2026 Loser of the Year
Joined: Sep 2013
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From: New Or-leens Loo-z-anna
There should be a shop that sells nothing but trans related parts- there are 2 or 3 in Kansas City that I've used. Prices vary a little between them, I usually go to the same one because the guys there seem to have a better handle on what's needed and I don't forget something. Rubber, paper and faced clutches runs about $125 IIRC. Add a front pump bushing, the 10 vane pump kit, and a filter. The ones I usually see are smoked big time so I usually get a convertor too. Out the door for between 200 and 250.
I forgot- I always get a shift kit- I prefer Superior, but had good luck with the Trans-Go kits too.
I forgot- I always get a shift kit- I prefer Superior, but had good luck with the Trans-Go kits too.
the transmission now has................223,000 miles on it.
Who said 700R4(s) don't hold up well?................LOL!
Le Mans Master
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From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
Must be an 89 or later 700R-4. The rear planetary gears were not real great before that. I worked at a Chevy dealer in 85-86. They had 9 parts delivery trucks. In the span of one week 6 of them blew the rear planetary gears apart. And that was back when warranty paid 14hours to R&R and rebuild.
Easy to tell the new style- the inner gearset has an oil slinger pressed on and the outer gear has chamfered edges and a line on one of the teeth the parking lock goes into.
Easy to tell the new style- the inner gearset has an oil slinger pressed on and the outer gear has chamfered edges and a line on one of the teeth the parking lock goes into.
Thread Starter
2026 Loser of the Year
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From: New Or-leens Loo-z-anna
Must be an 89 or later 700R-4. The rear planetary gears were not real great before that. I worked at a Chevy dealer in 85-86. They had 9 parts delivery trucks. In the span of one week 6 of them blew the rear planetary gears apart. And that was back when warranty paid 14hours to R&R and rebuild.
Easy to tell the new style- the inner gearset has an oil slinger pressed on and the outer gear has chamfered edges and a line on one of the teeth the parking lock goes into.
Easy to tell the new style- the inner gearset has an oil slinger pressed on and the outer gear has chamfered edges and a line on one of the teeth the parking lock goes into.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
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From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
That's good news. It should have the updated rear planetary set and a 10 vane pump. Just replace the rings in the pump with the hardened rings and drive on, provided the rest of the pump looks good.
Thread Starter
2026 Loser of the Year
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From: New Or-leens Loo-z-anna
Thanks for the replacement info!
Thread Starter
2026 Loser of the Year
Joined: Sep 2013
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From: New Or-leens Loo-z-anna
I got side-tracked with the purchase of a complete soft top assembly!The trans. Rebuild is still on the list though.
Maybe in another month...I'll post the pics in my build thread.
Team Owner
Joined: Jul 1999
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From: Orange Park Florida
he has helped my greatly over the years with auto trans issues, so keep your ear to the ground.....
